IMPROVEMENT IN NUTRIENT QUALITY OF CATTLE DIET AND MANURE
IN URBAN AND PERI-URBAN AREAS
BY
KATUROMUNDA SYLVESTER
B. Sc. Agric.; Dip. Educ.; M. Sc. Agric.; MUK
A THESIS
SUBMITTED TO THE SCHOOL OF GRADUATE STUDIES
OF MAKERERE UNIVERSITY
IN PARTIAL FULFILMENT OF THE REQUIREMENTS
FOR THE AWARD OF THE DEGREE OF DOCTOR OF PHILOSOPHY OF
MAKERERE UNIVERSITY
MAY 2010
DECLARATION
I declare that the work presented in this thesis is my own and that it has not been submitted
for a degree in any other University.
--------------------------------------------
--------------------------
KATUROMUNDA SYLVESTER
Date
This thesis has been submitted with our approval as the University Supervisors.
--------------------------------------------
--------------------------
Professor E.N. Sabiiti
Date
Makerere University
--------------------------------------------
--------------------------
Professor M.A. Bekunda
Date
Makerere University
ii
DEDICATION
Dedicated:
To my parents, Sylvester and Modesta who tirelessly laboured and sacrificed whatever they
had to make my future bright;
To my beloved wife, Dinah and children: Steven, Victor, Simon and Victoria, and to my
brothers and sisters for their love, support and inspiration.
iii
ABSTRACT
This study determined the effect of legume supplementation to dairy cattle fed P. purpureum
diet on feed intake and manuring quality of the ensuing faeces; and whether if properly
managed and applied in combination with mineral fertilisers in the field, cattle manure
enhances yield and quality of P. purpureum fodder. The study was carried out at Makerere
University Agricultural Research Institute Kabanyolo in three experiments. Experiment 1
determined the effect of legume supplementation to dairy cows offered P. purpureum basal
diet on feed intake, milk yield, faecal output and faecal nutrient concentration. Four diets
consisting of P. purpureum fodder fed ad libitum as a control, P. purpureum + Calliandra, P.
purpureum + Centrosema and P. purpureum + Desmodium were fed to dairy cows (average
weight 504 kg) in a 4 x 4 Latin square design. Legume supplements were offered at 0.52% of
the animal live body weight, and constituted 20% of the dry matter (DM) offered. Diets were
maintained for 28 days (14 days of adjustment to diets and 14 days for data collection).
Average daily DM and nutrient intake, apparent DM digestibility (ADMD), metabolisable
energy (ME) intake, milk yield, faecal output and faecal nutrient concentrations were
determined. Total DM intake, ADMD, ME intake and milk yield were significantly (P<0.05)
increased by legume supplementation. Daily intake of N, P, K and Ca were increased (P<0.05)
by the three legume supplements. Cows supplemented with Calliandra consumed the largest
amounts (P<0.05) of N. Among the supplemented diets, daily K intake was highest (P<0.05)
for Calliandra and Centrosema diets. Daily Ca intake differed significantly (P<0.05) among
the supplemented diets, and was 0.035, 0.043 and 0.046 g kg-1 for Calliandra, Centrosema
and Desmodium, respectively. Daily faecal output ranged between 4.32 and 4.87 kg cow-1 and
was highest (P<0.05) in Calliandra and Centrosema supplemented diets. Faecal–N, P and K
were highest in Calliandra, while faecal–Ca was highest in Calliandra and Centrosema diets.
iv
Experiment 2 determined the impact of method of storing faeces voided by dairy cows
offered P. purpureum–legume foliage meal diets on manuring quality of the resultant manure
composts. Faeces used in this experiment were produced following the same procedure as in
experiment 1. Faeces excreted daily by each cow on a particular diet were stored in a drum.
After two weeks of collection, faeces of each cow were emptied, mixed thoroughly, sampled
to obtain a faecal sample, divided into four equal portions and then subjected to four storage
methods for three months. Storage methods were: (i) placing faeces in pits (0.75 x 0.75 m)
and covering with soil (T1), (ii) placing faeces in pits lined with polythene sheet and covering
with another sheet (T2), (iii) placing faeces in pits and leaving the pits open (T3), and (iv)
stockpiling faeces on flat ground and leaving them uncovered (T4). After three months of
storage, the composted cattle manures were sampled to obtain manure samples and their
texture, colour, smell and biological activity assessed to determine their maturity and quality.
Both the faecal and manure samples were analyzed for OM, total N, NH4-N, P, K, C and pH.
Composts derived from faeces subjected to T3 and T4 methods were at advanced stages of
decomposition and exhibited features of maturity, namely fine texture, homogeneous colour,
inoffensive smell and presence of macroorganisms. But the T4 method produced poor quality
compost due to higher N and K losses. Changes in N concentrations were +0.18, -0.05, -1.39
and -1.80 g kg-1 for Calliandra, Desmodium and Centrosema diets and the control, respectively
with significant N losses in the control and Centrosema diets. Changes in K ranged between
-6.20 and -13.72 g kg-1 with the highest reduction occurring in the compost derived from faeces
of cows fed on the control diet. Changes in OM ranged between -38.23 and -123.53 g kg-1
with the greatest reduction in T3 and T4, suggesting that exposure of faeces to the atmosphere
accelerated the decomposition process. The concentrations of NH4-N in composts were 0.76,
0.43, 0.4 and 0.34 g kg-1 for T2, T4, T1 and T3, respectively and was highest (P<0.05) in T2.
v
The C:N ratios of composts from T3 and T4 were similar, but that of T3 was lower (P<0.05)
than those of T1 and T2. The concentration of N in T3 compost increased as a result of
higher rate of OM loss than that of N, and this in turn led to reduction of the C:N ratio.
In experiment 3, the effect of combining composted cattle manure with mineral fertilisers on
the yields and quality of P. purpureum fodder was evaluated in the greenhouse. The
experiment comprised twelve treatments arranged in a split plot design with three main plots,
four sub-plots and replicated four times. The experimental unit was a 25 cm diameter plastic
pot filled up to the height of 20 cm with 10 kg of sandy-clay loam soil. Main plots comprised
three soil amendments namely; sole composted cattle manure application (M), sole mineral
fertiliser (urea and SSP) application (F), and a combination of composted cattle manure and
mineral fertilisers (MF). Each of the amendments was applied at four rates which consisted
the control in which neither manure nor fertilisers were applied, low (L), medium (M) and
high (H) rates. Sole application of composted cattle manure at low, medium and high rates
(2.7, 5.4 and 10.8 ton, respectively), or in combination with mineral fertilisers at medium
(2.7 ton + 110 kg SSP + 110 kg urea) and high (5.4 ton + 220 kg SSP + 220 kg urea) rates
improved the growth of P. purpureum fodder in terms of LAIs and DM yields. The mean leaf
area indices (LAIs) of these treatments (ML, MM, MH, MFM and MFH) were 3.58, 3.69,
3.31, 3.28 and 3.56 respectively, and were higher (P>0.05) than 2.89 for the control. Fodder
DM yields from these treatments were 7.15, 6.99, 6.74, 6.80 and 7.01 ton ha-1, giving an
average of 7.0 ton ha-1. This amount of fodder, when supplemented with leguminous forages
and dairy meal at rates used in this study, would be able to support two dairy cows for a year.
Fodder obtained from ML, MM and MFH contained greater proportions of leaf than fodder
from the control, indicating that there was greater vegetative growth in these treatments than
vi
in the control. Since the leaves of plants usually contain less fibre and are thus easily digested
than stems, higher leaf proportion was an indication of improvement in fodder quality. The in
vitro organic matter digestibility (IVOMD) levels of fodder from all treatments were similar
but greater than that of the control.
The results of these experiments suggest that there is potential for improving the quality of P.
purpureum basal diet fed to lactating dairy cows through supplementation with legume
foliage particularly Calliandra. Better diet would result in higher milk yields for home
consumption and for sale, and higher faecal output and faecal nutrients for recycling within
the crop-livestock production systems. However, improvement in techniques of handling and
storing faeces following excretion is required in order to manipulate manure quality. Results
have shown that storing cattle faeces in open pits would be the most appropriate and low-cost
manure management intervention. The results also indicated that sole application of properly
managed cattle manure at low, medium and high rates (2.7, 5.4 and 10.8 ton, respectively) or
in combination with mineral fertilisers at medium (2.7 ton + 110 kg SSP + 110 kg urea) and
high (5.4 ton + 220 kg SSP + 220 kg urea) rates has the potential of improving the yields and
quality of P. purpureum fodder.
vii
ACKNOWLEDGEMENTS
I would like to express my most sincere thanks to my supervisors, Professor E. N. Sabiiti from
the Department of Crop Science and Professor M.A. Bekunda from the Department of Soil
Science, Makerere University for initiating and accepting to supervise this research. Their
guidance, technical advice, encouragement, suggestions and constructive criticisms directed
this study to a vivid end. Their willingness to sacrifice considerable time from their busy
schedules to attend to this study made it a success. Working with them and gaining from their
experience and knowledge in agricultural research has been an enriching experience in my
academic life. I am really proud of them and I appreciate their efforts to make me a
researcher. I must also express my gratitude to Doctor D. Mpairwe from the Department of
Animal Science and Doctor J. S. Tenywa from the Department of Soil Science for their
encouragement and suggestions on this study.
I am very grateful to Prof. E. N. Sabiiti not only for supervising me but also for securing a
scholarship for me from Rockefeller Foundation and additional funding from Sida/SAREC.
Importantly too, Prof. Sabiiti’s jovial nature, sense of humour, optimism and parental
guidance at times when I felt defeated and almost giving up kept me striving till the end of
the programme.
I sincerely thank Doctor Mary-Silver Rwakaikara, who was the Director of Makerere
University Agricultural Research Institute Kabanyolo when I was conducting experiments for
allowing me to use facilities of the Institute. Her acceptance was very reassuring. I am also
grateful to the technical staff at the Institute, for their invaluable assistance when I was
viii
conducting the experiments. I am greatly indebted to Mrs. Ruth Mubiru of Animal Science
Department for assisting me in the laboratory analyses of my samples. The assistance of
Constantine Katongole and Sadhat Walusimbi of Animal Science Department when I was
conducting statistical analyses is highly appreciated.
I am also grateful and sincerely appreciate the moral support, a sense of security and
belonging given to me by my wife and children. I thank my brothers and sisters, and all my
friends for their many words of encouragement, which kept me pushing on.
I would like to express my deepest gratitude to Rockefeller Foundation for sponsoring part of
my research work and tuition, and to Sida/SAREC for providing extra funding, which
enabled me complete the research.
To you all who contributed towards this research and have been inadvertently omitted, I ask for
pardon. I pray that the Almighty God, from whom all good things come, rewards you
abundantly!
ix
TABLE OF CONTENTS
PAGE
DECLARATION ...................................................................................................................... ii
DEDICATION ......................................................................................................................... iii
ABSTRACT ............................................................................................................................. iv
ACKNOWLEDGEMENTS ................................................................................................... viii
TABLE OF CONTENTS .......................................................................................................... x
LIST OF TABLES .................................................................................................................. xv
LIST OF FIGURES ............................................................................................................... xvi
APPENDICES………………………………..…………………………………………….xvii
CHAPTER ONE ..................................................................................................................... 1
GENERAL INTRODUCTION .............................................................................................. 1
1.1
Background ................................................................................................................... 1
1.2
Justification ................................................................................................................... 5
1.3
Specific objectives of the study .................................................................................... 8
1.4
Hypotheses ................................................................................................................... 8
CHAPTER TWO .................................................................................................................. 10
LITERATURE REVIEW .................................................................................................... 10
2.1
Importance of urban/peri-urban smallholder agriculture ............................................ 10
2.1.1 Role of urban/peri-urban agriculture in household food security and nutrition ......... 11
2.1. 2 Provision of employment and income for the disadvantaged urban dwellers ............ 13
2.1.3 Role of urban/peri-urban agriculture in the recycling of urban wastes ...................... 14
2.2
Effect of human population growth in urban areas on agriculture ............................. 14
2.3
Effect of agricultural intensification on soil fertility and productivity ....................... 15
x
2.4
Urban and peri-urban dairy farming ........................................................................... 16
2.5
Pennisetum purpureum (Napier grass) as a fodder crop ............................................. 17
2.6
Supplementary feeding ............................................................................................... 20
2.6.1 Effects of supplementing roughages with legume foliage on feed intake and
digestibility ................................................................................................................. 20
2.6.2 Effect of supplementing roughages with legume foliage on milk yields .................... 21
2.6.3 Dietary effects on faecal output in ruminant livestock ............................................... 22
2.6.4 Dietary effects on the mineral content in faeces and urine ......................................... 23
2.7
Management of livestock manure ............................................................................... 26
2.7.1 Animal excreta collection and storage ........................................................................ 26
2.7.2 Composting cattle excreta ........................................................................................... 28
2.8
Utilisation of livestock manure as a soil amendment in the crop-livestock
production systems.......................................................................................................31
CHAPTER THREE .............................................................................................................. 35
EXPERIMENTAL ................................................................................................................ 35
3.1.0
EXPERIMENT 1: Improving the quality of diet and manure by
supplementing Pennisetum purpureum offered to lactating dairy
cattle with legume foliage meal ............................................................................. 35
3.1.1
Introduction .............................................................................................................. 35
3.1.2
Materials and methods ............................................................................................ 37
3.1.2.1
Experimental design and management ................................................................... 37
3.1.2.2
Diets and feeding management ............................................................................... 37
3.1.2.3
Sampling procedure and treatment of feed and faecal samples .............................. 38
3.1.2.4
Milk yields and composition………………………………………………………39
3.1.2.5
Chemical analysis of feed and faecal samples ........................................................ 40
xi
3.1.2.6
Estimation of energy content .................................................................................. 40
3.1.2.7
Statistical analysis of data ....................................................................................... 41
3.1.3
Results ..................................................................................................................... 42
3.1.3.1
Chemical composition of experimental feeds and faeces ....................................... 42
3.1.3.2
Feed intake and digestibility, and faecal output...................................................... 45
3.1.3.3
Nutrient intake and excretion in faeces ................................................................... 47
3.1.3.4 Prediction of faecal output (FO) and the quantities of N and P excreted in faeces . 49
3.1.4
Discussion ............................................................................................................... 52
3.1.4.1
Chemical composition (nutrient content) of experimental feeds and faeces .......... 52
3.1.4.2
Feed intake and digestibility, and faecal output...................................................... 53
3.1.4.3
Nutrient intake and excretion in faeces ................................................................... 53
3.1.4.4
Prediction of the amounts of faeces excreted ......................................................... 55
3.1.4.5
Prediction of the amounts of N and P excreted in faeces ....................................... 55
3.1.4.6
Implications of increased faecal and nutrient excretion ......................................... 56
3.2.0
EXPERIMENT 2: Physical and chemical characteristics of composted
cattle manures as influenced by faecal storage method ......................................59
3.2.1
Introduction .............................................................................................................. 59
3.2.2
Materials and methods ............................................................................................. 60
3.2.2.1 Experimental design and management .................................................................... 60
3.2.2.2 Sampling procedure and treatment of manure samples ........................................... 61
3.2.2.3 Chemical analyses of manure samples .................................................................... 61
3.2.2.4 Statistical analysis of data ........................................................................................ 62
3.2.3
Results ...................................................................................................................... 63
3.2.3.1 Physical properties of composted cattle manures .................................................... 63
xii
3.2.3.2 The ammonium concentrations, C:N ratios and changes in the chemical
properties of composted cattle manures ....................................................................65
3.2.4
Discussion ................................................................................................................ 68
3.2.4.1 Physical properties of the composted cattle manures .............................................. 68
3.2.4.2 The ammonium concentrations, C:N ratios and changes in the chemical
properties of composted cattle manures ....................................................................70
3.3.0
EXPERIMENT 3: Growth characteristics and quality of Pennisetum
purpureum following the application of composted cattle manure and
mineral fertilisers ....................................................................................................74
3.3.1
Introduction ............................................................................................................. 74
3.3.2
Materials and methods ............................................................................................ 75
3.3.2.1
Production of composted cattle manure and soil preparation ................................. 75
3.3.2.2
Experimental design and measurements ................................................................. 75
3.3.2.3
Chemical analysis of samples ................................................................................. 78
3.3.2.4
Statistical analysis of data ....................................................................................... 79
3.3.3
Results ..................................................................................................................... 80
3.3.3.1
Growth Characteristics............................................................................................ 80
3.3.3.1.1 Leaf area index ........................................................................................................ 80
3.3.3.1.2 Fodder dry matter yields and in vitro organic matter digestibility ......................... 86
3.3.4
Discussion ............................................................................................................... 90
3.3.4.1
Growth Characteristics............................................................................................ 90
3.3.4.1.1 Leaf area index ........................................................................................................ 90
3.3.4.1.2 Fodder dry matter yields and in vitro organic matter digestibility ....................... 91
xiii
CHAPTER FOUR ................................................................................................................. 94
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS ...................................... 94
4.1
Summary and conclusions .......................................................................................... 94
4.2
Contribution of improved cattle diet and management of ensuing manure to the
productivity and sustenance of dairy production in urban and peri-urban areas…….97
4.3
Recommendations………………….……………………………………………….100
REFERENCES .................................................................................................................... 102
APPENDICES ..................................................................................................................... 123
xiv
LIST OF TABLES
TABLE
PAGE
1. Mean chemical composition of feeds fed to the lactating dairy cows at MUARIK …... 42
2. Mean chemical composition (quality) of faeces excreted by lactating dairy cows
fed on Pennisetum purpureum and different legume meal supplements …………...…. 44
3. Mean daily DM and OM intake, digestibility and faecal excretion by lactating
cows fed Pennisetum purpureum and different legume meal supplements ………...…. 46
4. Daily N, P, K and Ca intake and excretion by lactating dairy cows fed
Pennisetum purpureum and different legume meal supplements …………………..…. 48
5. Mean faecal output and composition for a 504 kg crossbred dairy cow fed on
Pennisetum purpureum fodder supplemented with dairy meal and legume meal …...... 57
6. Physical properties of the composted cattle manures that were sensually evaluated …. 64
7.
The ammonium concentrations, C:N ratios and changes in the chemical properties
of composted cattle manures as affected by legume supplementary feeding to dairy
cattle offered Pennisetum purpureum ………………………………..…………..……. 66
8. The ammonium concentrations, C:N ratios and changes in the chemical properties
of composted cattle manures as affected by faecal storage methods …………….……. 67
9. Characteristics of composted cattle manure and soil that were used in the
greenhouse experiment (on DM basis) ……………………………………..…….…… 75
10. Description of the treatments …………………………………………………….……. 77
11. Mean leaf area index of Pennisetum purpureum fodder at harvesting stage ……….…. 82
12. Dry matter yields, morphological fractions and IVOMD of Pennisetum purpureum
fodder as influenced by the application of composted cattle manure alone, mineral
fertilisers alone and composted cattle manure + mineral fertiliser combinations ….…. 87
13 Effects of composted cattle manure and mineral fertilisers on chemical
composition of P. purpureum fodder ………………………………………..…………89
xv
LIST OF FIGURES
FIGURE
PAGE
1. Linear regression of faecal output of crossbred dairy cows fed P. purpureum diet
and different legume meal supplements on apparent dry matter digestibility ….…….. 50
2. Increase in the leaf area index of Pennisetum purpureum plants as growth period
advances ……….…………………………………………………..……..…….…….. 81
3. Synthesis model of improvement in nutrient quality of cattle manure for utilisation
in the urban and peri-urban areas …………………………………………..….……. 98
xvi
APPENDICES
FIGURES
PAGE
1. Rainfall distribution and mean maximum temperature variation at Makerere University
Agricultural Research Institute Kabanyolo from July 2004 to February 2005 .…..… 123
APPENDIX TABLES
1
Experimental design for experiment 1 …………………………………..………..… 124
2
Changes in OM concentrations as affected by legume supplementary feeding
to dairy cattle offered P. purpureum basal diet ……………….……………..……… 124
3
Changes in total N concentrations as affected by legume supplementary feeding
to dairy cattle offered P. purpureum basal diet ………………….………………..… 125
4
Changes in total P concentrations as affected by legume supplementary feeding
to dairy cattle offered P. purpureum basal diet ……………….……………….….… 125
5
Changes in total K concentrations as affected by legume supplementary feeding
to dairy cattle offered P. purpureum basal diet ………….…………………….….… 125
6
Changes in pH as affected by legume supplementary feeding to dairy cattle
offered P. purpureum basal diet ………………………………………………….… 126
7
Changes in OM concentrations as affected by faecal storage methods ………….… 126
8
Changes in total N concentrations as affected by faecal storage methods …….…… 126
9
Changes in total P concentrations as affected by faecal storage methods …….….… 127
10 Changes in total K concentrations as affected by faecal storage methods …….…… 127
11 Changes in pH as affected by faecal storage methods ……………………………… 127
12 Concentrations of NH4-N in faeces and composted cattle manure …………….…… 138
xvii
CHAPTER ONE
GENERAL INTRODUCTION
1.1
Background
Uganda’s agriculture is mainly smallholder based, and accounts for over 90% of the total
agricultural output (PMA, 2000). In spite of the relatively favourable climatic conditions,
Uganda’s agriculture registers as one of the lowest productive sectors in the World. Key
among the causes are limited access to agricultural support services such as extension
services, food processing technologies, limited market information, high cost of inputs and
low price levels for agricultural products associated with production of low-value crops
(MFPED, 2004; PMA, 2000). Smallholder resource-poor farmers who dominate the
agricultural sector cannot afford expensive input technologies which can boost agricultural
production. For instance, use of inorganic fertilisers by smallholder farmers is associated
with several constraints, including limited accessibility and high cost (Makokha et al., 2001;
Woomer and Muchena, 1996). The soil protection techniques, particularly the long fallow
periods under traditional shifting cultivation, which used to allow soils to regenerate are no
longer sufficient (Nandwa and Bekunda, 1998; Tenywa, 1997). Thus the declining soil
nutrient content as a result of continuous cultivation is adversely affecting the productivity of
smallholder farms, particularly in urban/peri-urban areas, and consequently the incomes and
food security of farmers (Zake et al., 2003). One of the strategies to overcome these soil
constraints is intensification through integration of crop and livestock activities (Blackburn,
1998). Integration will promote utilisation of alternative sources of crop nutrients such as
crop residues, livestock manure and biomass transfer from trees and shrubs planted along the
farm boundaries (Delve et al., 2001; Mafongoya and Nair, 1997). However, to increase the
1
productivity of both crops and livestock, more inputs and improved technology application
are required (Mugisa, 2002; Mugisa et al., 1999).
Livestock are a crucial component in the smallholder mixed farming systems. In addition to
being important as producers of high quality protein-rich foodstuffs, livestock provide farmers
with an opportunity to diversify the risk of relying solely on crop production, to use labour
more efficiently, to have another source of cash, to be self employed especially women, and
to add value to crop wastes by turning them into useful products (Nambi-Kasozi et al., 2004;
Ehui et al., 1998; Mugisa et al., 1999). The animal manure can be used to produce biogas for
cooking and lighting, thus reducing on the problem of waste disposal and eliminates offensive
odours associated with huge piles of manure (NEMA, 1998). In addition, manure is a key
resource for sustaining productivity of smallholder farming systems in low-income fooddeficit countries (Giller et al., 2002; Fresco and Steinfeld, 1998).
With good management, livestock can make a positive contribution to the environmental
quality. For instance, owning livestock is a great motivation to plant forage bearing trees and
shrubs, grass contours and pasture, all of which help control soil erosion, conserve water and
increase plant biodiversity (Blackburn, 1998). But the most significant link between
urban/peri-urban agriculture (UPA) and the environmental and public health is waste
management. Urban waste production is growing in all cities globally, and UPA can serve as
one of the tools for dealing with urban wastes including cattle manure, both as an end-use and
as a treatment technique (Nambi-Kasozi et al., 2004).
2
Uganda’s livestock rearing systems have evolved over time to suit the various agroecological zones and the socio-economic settings. In the urban/peri-urban areas, stall-feeding
has been adopted as the most applicable and productive system of livestock rearing
(Tumutegyereize et al., 1999). It was vigorously promoted in the late 1980's by the
government, non-governmental organizations (NGO’s) and churches (Nsubuga, 1992). The
main objectives were to provide employment particularly for women who spent most of the
time at home taking care of their families, improve the nutritional status of the rapidly rising
urban human population through increased milk production and increase family income
through surplus milk sales (Kabirizi and Drania, 1997).
UPA encompasses all agriculture practices within and around cities which compete for land,
water, energy and labour resources that could also serve other purposes to satisfy the
requirements of the urban population. Important sectors of UPA include horticulture,
livestock, fodder and milk production, aquaculture and forestry (FAO-COAG, 1999).
According to Mougeot (2000a), UPA is an industry located within (urban) or on the fringe
(peri-urban) of an urban centre, which produces and supplies food and non-food products
using mainly human and material resources and services largely found in and around that
urban area. UPA is currently practiced by millions of people around the world and it has
been expanding since the late 1970s in many parts of the developing world. This expansion
has been regarded as a response to the market demands arising from rapid urbanization
(Smith and Olaloku, 1998). Development organizations have promoted UPA because it
provides food and economic opportunities for people who live at or near subsistence levels.
3
In addition to producing food for feeding their families and generating income, urban
farmers put idle land to productive use and recycle wastes. Livestock, particularly
ruminants, make a positive contribution in providing cost-effective means of disposal of
wastes from agro-processing industries and markets (Nambi-Kasozi et al., 2004). For
instance, cane molasses, cottonseed meal, sunflower meal, soybean meal, maize and rice
brans, brewery waste, blood meal, bone meal and fish meal all are agro-industrial
byproducts that are disposed of as wastes. These wastes, by serving as feedstuffs, contribute
a significant fraction of the nutrients that livestock consume and provide environmentally
safe and profitable means of industrial waste disposal. The positive effect of UPA on the
environment could be further enhanced if the manure from livestock is effectively recycled.
High annual growth rate of Uganda’s population (3.2% between 1991 and 2002), coupled
with urbanization is exerting massive pressures on food supplies, and is also responsible for
the increasing over-use of natural resources (MFPED, 2004; UBOS, 2002). Meeting the food
needs of a growing and urbanizing population with rising incomes will have profound
implications for UPA production in the coming decades. One of the key challenges facing
agricultural intensification in the 21st century is the issue of soil degradation, which adversely
affects crop yields (Murwira et al., 1995). In their review of literature and research findings
which addressed the types and coverage of soil constraints to crop productivity, Woomer and
Muchena (1996) reported nutrient limitation, insufficient soil moisture, toxicity and erosion
as the major constraints contributing to Africa’s dilemma of population growth outpacing
agricultural productivity.
4
Therefore, there is a need to develop appropriate technologies that can restore, enhance and
sustain the productivity of UPA. Future increases in the productivity of UPA will have to
come primarily from increases in output per unit of land already committed to agriculture.
This strategy requires farmers to use the available nutrient resources more efficiently and at
the same time conserve and regenerate the resource base. Locally available renewable inputs
such as animal excreta should be substituted, where possible, for the imported mineral
fertilizers or strategically combined. Giller and Wilson (1991) noted that in both developing
and developed countries, it is increasingly being realized that there is need for sustainable
agriculture, one which can feed the population of the world but not at the environmental cost
exacted by present day intensive farming practices.
1.2
Justification
For the past two decades or so, UPA has been expanding globally and has eventually become
an important sector in urban and peri-urban areas of the developing world. Its expansion has
been attributed to the market demand for its products arising from rapid urbanization and
population growth in towns and cities (Smith and Olaloku, 1998; Steinfeld, 1998).
International Food Policy Research Institute (IFPRI) estimates that for the developing world
as a whole, urban populations are likely to overtake rural populations before 2020, and a new
kind of food system will be needed to supply affordable, safe food to the cities (PinstrupAndersen et al., 1999). Governments are increasingly recognizing UPA as an important
component of urban development and environmental management (FAO-COAG, 1999;
Streiffeler, 2000). Its ecological advantages, particularly the possibility to utilise organic
wastes thereby ensuring a cleaner environment, have been observed (Nambi-Kasozi et al.,
5
2004). Also, its practical relevance for the nourishment and potential to relieve food
insecurity of the urban population has been noted (Armar-Klemesu, 2000). An important
social aspect of UPA is the provision of employment and income, especially to women as
they are the majority of those practicing it (Hovorka, 2006; Engle, 2000). Thus, the dramatic
increase in the rate of urbanization and size of cities over recent decades gives UPA a new
significance for food security and poverty alleviation, particularly among the urban poor.
However, agricultural land in urban/peri-urban areas is becoming very scarce requiring the
adoption of intensification-oriented technologies on the spaces available for cultivation
(FAO-COAG, 1999). But in the absence of appropriate management practices, intensification
can lead to soil degradation (Lal, 2001; Smaling, 1993). For instance, through sampling and
analysis of soils and observation of crops during extensive field tours, soil nutrient depletion
was identified as the major constraint to obtaining optimum maize grain and fodder yields in
the urban/peri-urban areas of central Uganda (Katuromunda et al., 2001; Mugisa et al.,
1999). The same studies showed that integration of forage legumes into maize and P.
purpureum (Napier grass) enhanced fodder and milk production, with commensurate
increase in profitability of the urban/peri-urban smallholder farming. It is envisaged that the
productivity of urban/peri-urban smallholder farming could further be enhanced if the
manure produced by dairy cattle was adequately managed and recycled back into the soil.
Recycling this manure through application to P. purpureum fields could probably boost
fodder production, which would in turn be reflected in increased livestock products.
6
However, few studies have been conducted to quantify the amounts and to determine the
fertiliser value of manure produced by dairy cattle in the urban/peri-urban smallholder
production systems of Uganda. Yet, in order for farmers to accurately plan for on-farm
manure nutrient generation and utilization, estimates of manure production and composition
are needed. Also, information on how this manure could be efficiently managed so as to
maintain its fertiliser value and therefore maximize its use efficiency as a soil amendment is
scarce. In addition, there is insufficient information on strategic supplementation of cattle
manure with the most limiting nutrients in form of mineral fertilizers so as to maximize
crop/fodder production.
Therefore, the general objective of this study was to investigate whether legume
supplementary feeding to dairy cattle offered P. purpureum basal diet improves feed intake
and manuring quality of the ensuing cattle faeces; and whether if properly managed and
applied in combination with mineral fertilisers in the field, cattle manure enhances yield and
quality of P. purpureum fodder. The resultant productivity gains are likely to increase food
(especially milk and milk products) and income (from milk sales) available to the urban/periurban households with low food purchasing power. For this reason, the current study is in
line with the strategies of the Poverty Eradication Action Plan and the Millennium
Development Goals aimed at providing sufficient food to the population, promoting
economic growth and eradicating poverty (PMA, 2000). It is also important to note that
intensive stall-feeding practices could increase nutrient losses and jeopardize long-term soil
productivity if technologies that can effectively capture and recycle the nutrients voided by
stall-fed livestock are not available.
7
1.3 Specific objectives of the study
The specific objectives of the study were to:
1.
Quantify the effect of legume supplementary feeding to dairy cows offered P.
purpureum basal diet on feed intake, milk yield, faecal output and faecal nutrient
concentration for improved animal and soil productivity.
2.
Develop regression models for predicting faecal output and the amounts of N and P
excreted in faeces by dairy cows offered P. purpureum diet and supplemented with
legume foliage meal, so as to accurately plan for manure utilisation as soil amendment.
3.
Identify the most effective method of storing cattle faeces which will lead to production
of compost with better manuring quality.
4.
Evaluate the effect of combined application of composted cattle manure and mineral
fertilisers on the yield and quality of P. purpureum fodder for better animal nutrition.
5.
Evaluate the contribution of improved cattle diet and management of ensuing manure to
the productivity and sustenance of the smallholder dairy production in urban and periurban areas.
1.4
Hypotheses
The following hypotheses were tested:
1.
Supplementing P. purpureum basal diet offered to dairy cows with legume foliage
meal might improve the quality of diet which in turn will result into higher feed
intake, milk yield and excretion of larger amounts of faeces with better manuring
quality.
8
2.
Regression equations can be developed to predict faecal output and faecal-N and P by
dairy cows based on intake of DM, nutrients and apparent dry matter digestibility.
3.
The method of storing faeces excreted by dairy cows fed P. purpureum basal diet and
supplemented with legume foliage does not influence the maturity period and the
manuring quality of the resultant manure compost.
4.
Supplementary application of mineral fertilisers to fields that have received
composted cattle manure has no effect on nutrient uptake and the resultant yields and
quality of P. purpureum fodder.
5.
Improvement of cattle diet and management of the resultant manure does not have a
positive impact on the productivity and sustenance of the smallholder dairy production
practiced in urban and peri-urban areas.
9
CHAPTER TWO
LITERATURE REVIEW
2.1
Importance of urban/peri-urban smallholder agriculture
Food and Agriculture Organisation-Committee on Agriculture (FAO-COAG, 1999) defined
“urban” agriculture as small plots within a city that are used for growing crops and raising
small livestock or dairy cows for own-consumption or sale in the neighbourhood markets.
Peri-urban agriculture was defined as farm units close to town which operate intensive semior fully commercial farms to grow vegetables and other horticulture, raise chickens, dairy
cows and other livestock. The majority of urban/peri-urban farms are small, hence the term
smallholder. Waters-Bayer and Bayer (1992) defined smallholders as those families which
practice labour-intensive forms of farming using low levels of purchased inputs and small
plots of land to produce agricultural products. There is a worldwide growing recognition of
the importance and significance of UPA. Sawio and Spies (1999) summarised the important
roles that UPA plays as bridging the gap between food demand in the cities and the poor
rural food production and supply systems, augmenting food security of urban households
whose food purchasing power from the markets is low, employment and income generation
among the unemployed and low-income urban households, provision of supplementary
income to the poorly paid urban dwellers, provision of economic investment alternative for
better-off urban dwellers who have interest in investing in intensive market gardening, meat
and milk production, and provision of opportunities for recycling biodegradable wastes.
10
In Uganda, urban agriculture started in the early 1970’s as a result of economic decline,
crippled food distribution system, reduction of wages, institutional breakdown and civil
conflict that characterized the social life (Obbo, 1991). Since then, the urban population has
grown considerably and an increasing number of vulnerable households have turned to urban
farming as an alternative source of food, as a means of savings on food expenditure and also
a way of generating income. Initially it was mainly a survival strategy for the poorest of the
urban poor, but increasingly, farming activities gained importance among the urban poor and
also among a significant proportion of low and medium income earners (Maxwell, 1994).
Most urban farmers in Uganda like in other developing countries are women who embrace it
as a way of supplementing their families’ incomes and food supply. Although the largest
proportion of harvest is consumed by the producers, the surplus can be traded. Land and
space for agriculture is limited and when available, it has to compete with a multiple of other
uses.
2.1.1 Role of urban/peri-urban agriculture in household food security and nutrition
In sub-Saharan Africa, UPA is increasingly being seen as an alternative urban food strategy
that could be employed to alleviate some of the impacts of structural adjustment policies on
the urban poor (Hasna, 1998). The crisis of the urban formal economy, falling real wages and
decreased opportunity for wage employment are the forces that are driving the need for such
a source of food. Urban residents all over the developing world cultivate urban plots and /or
keep livestock in order to sustain their living. Different modes of urban farming are
embraced by the different socio-economic groups. Swift and Hamilton (2001) noted that due
to inadequacy of formal safety precautions against food insecurity, urbanites have developed
11
their own responses to food insecurity, including urban gardening, direct diversification of
income-earning activities into self-employment and transfers of food or income through
informal and kinship networks. Hovorka (2006) pointed out that UPA is the deliberate effort
of urban women to provide for themselves and the people for whom they are responsible, the
security of a source of food that is not dependent on cash incomes or fluctuating markets.
The UPA reduces food insecurity by increasing access to food among households. It is an
important coping strategy of the urban poor, many of whom would starve if they weren't
farming (Makumbi, 2004). Even a small fraction of overall food consumption coming from
UPA can greatly affect household food security if it comes at periods of acute need (Ruel et
al., 1998). Studies by Maxwell et al. (1998) revealed a significant improvement in nutrition
among Kampala households that practiced agriculture within the city. Among the low-income
groups, self-produced food could cover a considerable share of a household's total food intake
and could save cash income that otherwise would be spent on food.
Urban/peri-urban agriculture also enhances the freshness of perishable foods reaching urban
consumers, thus increasing overall variety and the nutritional value of food available. Poor
households cannot regularly afford buying perishable foodstuffs containing essential
nutrients, which are especially important for children. But even the wealthy urban dwellers
sometimes face difficulties in obtaining sufficient amounts of perishable foodstuffs like milk,
fruits and vegetables during times when transportation and distribution channels from
countryside to the city breakdown. Under such circumstances, instead of being supplemental
UPA becomes the main food source to urban consumers (Nugent and Egal, 2000). In
12
addition, when food items are produced close to where they are demanded, transportation
costs are minimized since farmers are able to take their produce to the markets either on foot
or by bicycle.
2.1. 2 Provision of employment and income for the disadvantaged urban dwellers
Urban/peri-urban agriculture offers opportunities for employment to a significant proportion
of the world population. In 2000, UPA was estimated to involve 800 million urban residents
worldwide in income-earning and/or food-producing activities (Prain, 2000). Women formed
the majority of urban/peri-urban farmers, as most of them were not employed in the formal
sector of the urban economy and, instead were more concerned with childcare and household
responsibilities (Mougeot, 2000b).
Urban/peri-urban agriculture generates a significant share of the household income for the
urban households engaged in it (Bakker et al., 2000). An agricultural enterprise, no matter
how small, offers new opportunities to families and communities living in material poverty.
The little daily income gained by selling agricultural products like milk brings new
opportunities to farm households, raises hopes as well as living standards (Maxwell et al.,
1998). According to Mugisa et al. (1999), market-oriented dairy production in the peri-urban
areas of central Uganda acted as an avenue for smallholder women farmers to increase their
income, which promoted gender equity.
13
2.1.3 Role of urban/peri-urban agriculture in the recycling of urban wastes
Urban/peri-urban agriculture makes a significant contribution to the environmental quality by
utilising urban wastes as livestock feed and by providing more green space through planting
of forage bearing plants (Nambi-Kasozi et al., 2004; Sawio and Spies, 1999). In addition to
the crop wastes that are accumulating in urban markets, the processing of agricultural
products that is carried out in urban areas gives rise to considerable amounts of wastes that
are environmentally unsafe for both humans and livestock. Such wastes include byproducts
from slaughter houses, cereal brans, seed cakes and brewery waste. By serving as livestock
feed, these wastes result in better animal productivity and a cleaner environment (NambiKasozi et al., 2004; MPMPS, 1998). According to Smit et al. (1996), UPA is the most
efficient tool available for transforming urban wastes into food and jobs. In addition, by
owning livestock, farmers are encouraged to plant forage bearing trees, shrubs and grasses,
all of which play an important role in soil and water conservation and increasing plant
biodiversity (Kabirizi, 2006; Blackburn, 1998).
2.2
Effect of human population growth in urban areas on agriculture
Enormous demographic and social changes are sweeping across sub-Saharan Africa, as it has
the most rapidly growing population of any region in the World (Bulatao et al., 1990). In
Uganda, the urban population increased rapidly from less than one million persons in 1980
(6.7% of total population) to 3 million (12.3% of total population) in 2002, representing a
more than three-fold increase (UBOS, 2002). The urban population continues to rise as new
trading centres emerge and the old ones develop into towns (Mukwaya, 2004). Ratta and
Nasr (1999) observed that the increase in population, urbanisation and income change
stimulate the intensification of agricultural systems and alter the prospects for sustained
14
economic development. Delgado, et al. (1999) noted that population growth, urbanisation,
and increasing incomes in the developing world will, over the next two decades, fuel a
heretofore unimagined growth in consumer demand for milk and meat products.
2.3
Effect of agricultural intensification on soil fertility and productivity
The increase in human population in the urban/peri-urban areas of Uganda has continuously
reduced the available land for agriculture. As a result, farmers have adopted intensificationoriented technologies in order to maximize production using the remaining cultivable land.
However, due to lack of appropriate soil management practices on some of the smallholder
farms, intensification has caused soil nutrient depletion (Katuromunda et al., 2001; Mugisa et
al., 1999). Substantial quantities of nutrients have been and continue to be lost through off
take in harvested products and crop residues.
Replenishment of soil fertility is likely to result in positive benefits associated with enhanced
crop/fodder production and increased soil biological activity. Soil fertility replenishment can
be achieved through application of organic materials and mineral fertilizers, or a combination
of both. However, the use of mineral fertilizers by the urban/peri-urban smallholder farmers
is still low due to socioeconomic constraints. Therefore, organic materials will continue to
serve as sources of plant nutrients for sometime. Rufino et al. (2007) observed that although
the absolute amounts of nutrients, particularly N that farmers may recycle with improved
manure management have limited impact on crop productivity, manure is often the sole input
available to farmers. Through research, nutrient limitations of organic materials can be
identified and rectified through strategic supplementation with small amounts of mineral
fertilizers.
15
2.4
Urban and peri-urban dairy farming
In Uganda, cattle rearing systems have evolved over time to suit the various agro-ecological
zones and the socio-economic setting. In the urban/peri-urban areas, stall-feeding (zero
grazing, cut and carry, green chop, soiling) has been adopted as the most applicable and
productive system of rearing dairy cattle (Tumutegyereize et al., 1999). It is an intensive
system where fodder grasses (such as Napier grass, Giant Setaria, Guatemala) and fodder
legumes (such as Lablab, Calliandra, Leucaena) are specifically grown for cutting and
transporting to the animals in stalls and the resulting manure returned to the gardens to
sustain soil fertility. In addition, animals are fed on agro-industrial by-products such as
brewery waste, cereal brans like maize bran and seed cakes like cotton and sunflower cakes.
Stall-feeding is capital and labour intensive as it involves rearing of expensive and high milk
yielding dairy cattle breeds. For stall-feeding to be profitable, farmers must be able to sell
milk at relatively high prices. This is the reason why stall-feeding is restricted to urban/periurban areas where the market for milk is readily available.
Owing to a multitude of constraints under which farmers operate, the genetic production
potentials of the dairy cattle are far from being fully exploited. One of the major problems is
lack of sufficient, high quality forage all-year round (Saamanya, 1996). During the rainy
periods, there is plenty of forage but during the dry periods, forage becomes scarce and the
little that may be available becomes coarse with low nutritive value, palatability and
digestibility. Such forage cannot meet the nutrient requirements for livestock and as a result
the growth rates of young animals decline and milk output from lactating animals drops
tremendously (Brumby and Gryseels, 1985). Therefore, in order to maintain and optimize
16
livestock productivity during the dry periods, there is need to focus on other alternative feed
resources such as leguminous forage plants that persist during the dry periods, and crop
wastes. During harvesting season which coincides with periods of forage scarcity, crop
residues are produced, and they can serve as an alternative feed resource. However, the
feeding value of crop residues is low due to low levels of readily fermentable and
metabolisable energy (ME), CP, minerals and vitamins and high levels of fibre and lignin
(Sundstol and Owen, 1984). Thus their usage as livestock feeds requires supplementation
with protein-rich feedstuffs such as commercial concentrates and leguminous forages (Smith
et al., 1989). Forage legumes are of high nutritive quality especially in CP and thus can serve
as supplements to roughages like crop residues and dry herbage (Mpairwe et al., 1998).
Mpairwe et al. (2003) further observed that compared to commercial concentrates and seed
cakes, leguminous forages are more economical under smallholder dairy production systems.
2.5
Pennisetum purpureum (Napier grass) as a fodder crop
During the study conducted by Katuromunda (2001), the botany, origin and distribution, the
agronomy, herbage yield and chemical composition and utilisation of P. purpureum as a
livestock feed was extensively reviewed. In summary, P. purpureum is a perennial grass with
a creeping rhizome and usually attains a height of 2-6 m at maturity, depending on the soil
type and climatic conditions under which it is grown. It is widespread in the tropical and subtropical regions of the world. P. purpureum is the dominant grass species in the Pennisetum
purpureum grassland in Uganda, and is mostly found around the shores of Lake Victoria,
extending to about 40 km from the lake. It is essentially a grass for hot and humid regions,
preferably below 1500 m above sea level (Skerman and Riveros, 1990). It grows best in high
17
rainfall areas of not less than 1000 mm annually. Its well-developed root system enables it to
withstand drought and stay green during dry seasons (Skerman and Riveros, 1990).
Pennisetum purpureum is mainly established using stem (cane) cuttings (Wolfang Bayer,
1990), with at least three nodes, one of which must remain above the soil when planted.
According to Boonman (1993), it can also be established using splits from young plants. The
planting method used does not have any significant effect on sprouting, growth and survival
of P. purpureum (Ssekabembe, 1998). A well-prepared seedbed is required so as to boost the
growth of planted cuttings. Deep ploughing to remove all obnoxious weeds such as, couch
grass (Digitaria scalarum) and spear grass (Imperata cylindrica) is necessary because these
weeds are very difficult to control once P. purpureum is fully established. Stem cuttings are
either inserted into the soil at an angle of 450, or buried horizontally in furrows. The optimum
time for harvesting P. purpureum fodder is when the canes are 0.6-0.9 m tall. However, the
first cutting should be done after the plants have accumulated a good amount of nutrient
reserves in the rootstocks (Sollenberger et al., 1988). According to Boonman (1993), P.
purpureum requires 100, 22 and 22 kg ha-1 of N, P and K respectively, in order to grow well.
When cutting and feeding it to cattle, large amounts of nutrients are transferred from the soil
to the feeding stall. Synders et al. (1992) reported that P. purpureum yielding 15-20 t ha-1
year-1 of DM can remove from soil up to 300 kg N, 150 kg P and 600 kg K.
18
Pennisetum purpureum fodder DM yield and nutritive quality depend on rainfall amount and
distribution, soil fertility, ambient temperature and the level of management such as,
manuring, cutting management, and weeding. The longer the cutting interval, the higher the
DM yields but less the nutritive quality. Yields can range from 2 to 19 t ha-1 year-1 on
unfertilized soils to 55 t ha-1 year-1 on fertilized soils with adequate water supply (Williams,
1980). Studies by Saamanya (1996) showed a gradual decline in the CP content and an
increase in the NDF as the cutting interval became longer.
As a livestock feed, P. purpureum is considered to be among the superior fodder producers in
the world (Boonman, 1993). It has also been reported that P. purpureum is non-toxic to cattle
and displays unusually high forage quality (Sollenberger et al., 1988). Grant et al. (1974)
observed that without supplementation, elephant grass could support daily production of 8-10
kg of milk per cow, and that it has been successfully used as sole feed for ruminants.
However, several researchers notably Mpairwe et al. (2003), Kabirizi et al. (2000), Muinga
et al. (1995) reported that the CP and ME values in P. purpureum were insufficient for
optimum milk production. They recommended that P. purpureum should be supplemented
with forage legumes and/or concentrates in order to improve DM intake, digestibility and
milk production.
19
2.6
Supplementary feeding
The aim of supplementation is to boost animal productivity by using small amounts of highly
nutritive feedstuffs to optimise the utilisation of cheap and readily available low-quality feeds
(roughages) and increase productivity. The supplement is expected to provide the critical
nutrients that are lacking in the roughage, particularly N, and to create a rumen environment
that is conducive for the release and utilisation of nutrients in the roughage (Mpairwe et al.,
2003).
2.6.1
Effects of supplementing roughages with legume foliage on feed intake and
digestibility
Legume foliage can serve as livestock feed supplement to roughages such as crop residues,
agro-industrial by-products and low quality forages, particularly during the dry season. The
legume foliage increases the efficiency of utilisation of roughages when fed at low levels of
supplementation by promoting voluntary feed intake and digestibility, and by providing
nutrients that are lacking in roughages, particularly crude protein. Muinga et al. (1995)
observed a significant (P<0.01) increase in feed intake with supplementation. Total DM
intake was 6.3, 7.6, 7.9 and 8.7 kg DM day-1 for unsupplemented P. purpureum diet,
supplemented with 1 kg or 2 kg of Leucaena, or 2 kg Leucaena together with 1 kg DM maize
bran, respectively. The apparent OM digestibility tended to increase progressively with
supplementation, however, the effect was not significant. In a related study, Kabirizi et al.
(2000) reported significant (P<0.05) increases in feed intake (8.8, 10.8, 12.0 and 12.3 kg DM
day-1) when P. purpureum basal diet offered to lactating dairy cows was supplemented with
increasing levels (nil, 2, 3 and 4 kg day-1) of Lablab hay.
20
According to Mpairwe et al. (2003), supplementation of maize/Lablab stover and oats/vetch
hay basal diets offered to dairy cows with increasing levels of Lablab hay (nil, 0.4, 0.8 and
1.2 % body weight (BW)) resulted in a significant (P<0.01) quadratic effect on total DM
intake. The total DM intake was 9.8, 11.0, 10.7 and 10.3 kg day-1 for maize/Lablab stover
diets and 9.7, 10.2, 11.6 and 11.2 kg day-1 for oats/vetch hay diets. The highest total DM
intake in maize/Lablab stover and oats/vetch hay diets was obtained at 0.4 and 0.8% BW
Lablab hay supplementation, respectively. The apparent DM digestibility in maize/Lablab
stover diets significantly (P<0.01) improved with Lablab hay supplementation, but not in
oats/vetch hay diets. In these studies, researchers have attributed the increase in feed intake to
increased ammonia concentrations in the rumen which in turn increase the digestion and
clearance of DM from the rumen. They observed that the presence of legume foliage
increases the activity of rumen microorganisms, which in turn increases the degradation of
fibre leading to reduced retention time of the digesta (Topps, 1997). However, the effect of
supplementing P. purpureum basal diet offered to dairy cows with dry milled foliage of
Calliandra, Centrosema and Desmodium on voluntary feed intake and digestibility has not
been adequately researched; hence the purpose of this study. In addition, these studies
neglected the changes in faecal output which could have occurred as a result of increased
feed intake and digestibility.
2.6.2
Effect of supplementing roughages with legume foliage on milk yields
Effect of supplementing roughages with legume foliage on milk yields and composition has
been extensively studied by several researchers, notably Muinga et al. (1992; 1995), Kabirizi
( et al., 2000; 2006), Katuromunda et al. (2000), Mpairwe et al. (2003), Juma et al. (2006).
Kabirizi et al. (2000) indicated that supplementation of P. purpureum with Lablab hay
21
significantly (P<0.05) increased fat-corrected milk yield but had no effect on the butterfat
content of milk. Similarly, the use of wheat bran and Lablab hay as supplements to cows fed
maize/Lablab stover and oats/vetch hay diets significantly (P<0.05) increased milk yield
(Mpairwe et al., 2003). Juma et al. (2006) reported that supplementing P. purpureum with
Clitoria ternatea, Gliricidia sepium and Mucuna pruriens significantly (P < 0.05) increased
daily milk yield. These studies confirm that utilisation of forage legumes as feed supplements
to low quality forages can be an effective way of increasing milk production by crossbred
dairy cows. Since the effect of supplementing roughages with legume foliage on milk yields
and composition has been extensively studied, not much emphasis will be put on this section
during the course of this study.
2.6.3 Dietary effects on faecal output in ruminant livestock
There are not many studies that have been done to estimate the quantities of faeces excreted
by dairy cattle under different feeding regimes, especially in the urban/peri-urban
smallholder farming systems. Some of the studies have shown that quantities of faeces
excreted vary considerably with composition of the diet fed to livestock, among other factors,
but in some experiments faecal output was unchanged. For instance, studies conducted by
Tomlinson et al. (1996) to determine the effects of level and source of dietary protein on N
excretion showed that linear increases in dietary CP did not affect the amounts of faeces
excreted, except the addition of calcium soaps of long-chain fatty acids and blood meal to the
diet. Conrad et al. (1964) observed that under free access to feed, dairy cows excreted a
constant amount of faeces per unit of body live weight (10.7 g DM kg-1 LW day-1) and
indicated that this faecal output was constant over a wide range of digestibilities. However,
Fernández-Rivera et al. (1995) observed a great variation in faecal output of ruminants
22
confined in stalls and fed ad libitum. This variation was attributed to the physiological stage
of the animals used (dry, pregnant and lactating), kind of feed offered (crop residues, grasses
with no or low levels of concentrate/legume hay supplementation) and breed of animals
(included breeds from tropical and temperate climates). Cattle with body LW ranging
between 81and 665 kg (mean, 300 kg) excreted faeces in the range of 3.7 and 16.2 (mean,
8.5) g kg-1 LW day-1. A regression analysis of daily faecal output per unit body LW (g kg-1
LW) on DM digestibility (g kg-1) revealed that faecal output decreases as DM digestibility
increases. From these studies, it is clearly indicated that faecal output in livestock varies
depending on the physiological stage of the animals, kind of feed offered and breed of
animals. Therefore, there is need to conduct similar studies to verify whether these
relationships would still hold when stall-fed crossbred dairy cows (reared in the urban/periurban smallholder dairy farming systems) are offered P. purpureum diet ad libitum and
supplemented with Calliandra, Centrosema and Desmodium foliage meal.
2.6.4
Dietary effects on the mineral content in faeces and urine
Several researchers have observed that livestock extract only a small portion of the major
nutrients that are fed to them to grow and to produce products such as meat and milk (Lekasi
and Kimani, 2003; Delve et al., 2001; Paul et al., 1998; Tomlinson et al., 1996; Powell and
Williams, 1995; Powell et al. (1994). The remaining nutrients are excreted in urine and feces.
It has been reported that about 75-95% of the N and P ingested by livestock is excreted.
According to Delve et al (2001), most of the P and about 60% of the N are excreted in the
faeces. Lekasi and Kimani (2003) observed that between 69-79% of total N was excreted in
faeces while the rest was in urine. The National Research Council (2001) reported that urine
is the major excretion pathway for readily available N, elemental K and Na. The excreted
23
elemental P, Ca and slow–release N from undigested protein are mainly contained in faeces
(Tomlinson et al., 1996; Morse et al., 1992). Powell and Williams (1995) observed that
urinary-N is readily lost through volatilization and leaching through the soil whereas faecalN is released slowly in the soil as the faeces decompose; and therefore, is more available for
recycling by plants.
According to research reports, the feeding programs followed by producers influence the
amounts of nutrients excreted in faeces and urine. Lekasi and Kimani (2003), Tomlinson et
al. (1996), Powell et al. (1994) and Morse et al. (1992) observed that feeding excess levels of
protein and P to livestock led to increased excretion of N and P. Tomlinson et al. (1996)
developed equations to predict N excretion based on N intake, DM intake, milk yield and
body weight. But they found out that milk was not a significant component of the prediction
equations when DM intake was also included. This was attributed to the fact that DM intake
was correlated with milk yield. Body weight was significant only in equations predicting
urinary-N. The only significant terms in the equation to predict daily excretion of faecal-N
were linear terms for N intake and DM intake. The equation developed for faecal-N excretion
states that:
Faecal-N (g) = 33.21 + 0.125 x N intake (g) + 4.877 x DM intake (kg); R2 = 0.66.
If DM intake was dropped in favour of milk yield, the resulting equation accounted for
almost as much of the variation in the dependent variable as the equation stated above.
Lekasi and Kimani (2003) also observed a linear relationship between the daily N intake (g
kg-1 LW) and the daily N excretion in faeces, which showed that as CP increased in the diets
so did the faecal N excreted.
24
Similar studies are needed to determine the effect of supplementing P. purpureum basal diets
fed ad libitum to stall-fed lactating dairy cows with Calliandra, Centrosema and Desmodium
foliage meal on mineral (N, P, K and Ca) concentrations in the faeces. Very few studies have
been carried out purposely to determine the effects of supplementing roughages fed to dairy
cows with legume foliage on the output and composition of faeces excreted with the view of
maximizing their use as a soil amendment. According to the literature reviewed, the majority
of researchers dealt mainly with the effects of feed quality, intake and digestibility on animal
productivity in terms of growth and milk output and neglected the effects of these factors on
faecal output and its manuring quality. Indeed some researchers notably, Sorensen et al.
(2003), Mpairwe et al. (2003), Delve et al. (2001) and Tomlinson et al. (1996) investigated
the effects of these factors on the output and quality of livestock excreta, but the basal diets
and supplements used were different from those fed to dairy cows reared in urban/peri-urban
areas of Uganda. In addition, the breeds of animals used were different. In other studies, the
legume supplements used were of different species from those used by smallholder farmers
in the urban/peri-urban areas of Uganda. Also the results of these studies showed a great
variation in the amounts and chemical composition of faeces excreted. This variation was
attributed to a number of factors including differences in the chemical composition of legume
supplements used, and the species, body sizes and physiological states of the animals.
Although the above studies neglected the value of animal excreta, other studies carried out
specifically on livestock manure have shown that if it is well managed and recycled it can
sustain or even increase the supply of livestock feed and soil productivity. Thus, along with
the research targeted at improving animal nutrition and productivity, simultaneous studies on
improvement and/or sustenance of soil fertility are necessary so as to raise the overall
25
agricultural productivity. For instance, there is need to develop improved animal excreta
handling and storage technologies that can enhance nutrient cycling in the mixed croplivestock production systems, for which part of this study is intended to address. Reducing
nutrient losses from livestock manure can improve the role of livestock in nutrient cycling
and lead to higher crop/forage yields, and in turn, animal production.
2.7
Management of livestock manure
Efficient management of nutrients in livestock manure is key to crop production, especially
for smallholder farmers who rarely use commercial fertilisers to maintain soil fertility. When
managed properly, the nutrients in manure can substitute for commercial fertilisers and thus
save money that would have been spent on fertilisers. Efficient management of livestock
manure would involve applying better handling methods and safety management practices
that reduce manure nutrient losses at various stages, right from excretion until field
application. It would also involve applying the manure in the cropping systems that
efficiently utilise the manure nutrients and at rates that do not exceed the assimilative
capacity of soil and crops. All these would require a better understanding of the causes of
nutrient losses from livestock manure at various stages.
2.7.1
Animal excreta collection and storage
The extent to which nutrients excreted by livestock can be returned to the soil and made
available to crops will depend on the way the manure is handled and stored. Reports by
Rufino et al. (2007) and Lekasi et al. (2003a) indicated that the type of floor and roof of the
animal housing system and the manner in which the animal excreta are collected and stored
before application to the field influence the nutrient concentration in livestock manure. Stall
26
feeding units with concrete floors without bedding that contain livestock whose feeding
regime included food supplements produced better manure than other systems (Lekasi and
Kimani, 2003). According to Paul et al. (1998), considerable nutrient losses, particularly of N
can occur through volatilization, leaching and runoff when animal excreta is left exposed to
weather conditions following excretion. Thomsen (2000) and Martins and Dewes (1992)
reported that the largest C and N losses from livestock manure occurred within 7-10 days
after excretion, which indicated that the frequency of manure removal from the stall has a
large influence on the amounts that may be recycled. Rufino et al. (2007) observed that
improved manure storage had little effect on increasing overall N cycling efficiency for the
poor farmers due to large N losses which occurred before storage.
These reports clearly indicate that improving the collection and storage methods of animal
excreta following excretion plays a role in the conservation of manure nutrients. Therefore,
basing on these reports one can deduce that heavy losses of manure nutrients are likely to be
occurring in the urban/peri-urban areas of Uganda where the majority of smallholder farmers
simply scrape animal excreta from stalls and heap it on bare ground in the open just adjacent
to the stalls. In some cases, by the time the excreta are collected from the stall for storage,
significant mass and nutrient losses due to trampling have already taken place. Studies on
manure collection and storage to determine the extent of manure nutrient losses under this
method of manure management and compare it with other alternatives are rare. Thus, there is
need to conduct more such studies and design better manure management strategies that can
address manure nutrient losses during collection and storage.
27
2.7.2
Composting cattle excreta
Livestock excreta require composting so that they decompose into manure before application
in the field. Composting is the controlled decomposition of organic residues. It transforms
raw organic wastes into biologically stable, humic substances that make excellent soil
amendments (Cooperband, 2002). The method of composting animal excreta is one of the
factors that affect the mineral concentration of composted animal manure, others being age
and species of the animal that produces the excreta, housing and rearing management, feed
ration and climatic conditions. The climatic conditions under which storage takes place affect
the rate of manure decomposition and the rate of nutrient losses through leaching and
volatilisation.
The principal requirement for a compost to be safely used as a soil amendment is its degree
of maturity and stability. Cooperband (2002) defined compost maturity as the degree of
humification (conversion of organic compounds to humic substances). Maturity is associated
with the ability of compost to support plant growth (Iannotti et al., 1993), whereas stability is
associated with changes in the physical and chemical properties of compost brought about by
microbial activity. Immature composts may contain phytotoxic substances such as phenolic
acids and volatile fatty acids (acetic, propionic and butyric) which inhibit plant growth (Inbar
et al., 1993). Competition for oxygen and nutrients between plants and microbes during
decomposition of immature composts also induces oxygen and nutrient deficiencies in the
root zone. Thorne and Tanner (2002) observed that immature composts have a high
‘‘temperature’’ which can damage plants, and in some areas immature composts created pest
problems. In contrast, mature composts are free from viable weed seeds and plant and animal
28
pathogens (Rynk et al., 1992). Also their organic matter contents become stable after 80-90
days of composting (Inbar et al., 1993). Well composted cattle manure is a stable, odourless,
fine textured and low-moisture content material that can be stored, or bagged and sold for use
as fertiliser on cropland (Eghball and Power, 1994). Rynk et al. (1992) noted that composting
improved the handling characteristics of livestock manure by reducing its volume and
weight.
A number of physico-chemical parameters have been proposed as useful indicators of
compost maturity and hence can be used for testing compost maturity. They include texture,
colour, odour, C:N ratio, pH value and levels of ammonium and nitrate. Lekasi et al. (2003a)
observed that manure derived from cattle faeces is regarded as fully decomposed and ready
for application when it turns into a fine textured loamy, dark brown or black and odourless
material or, material with a slight `earthy' and inoffensive smell. However, physical
properties such as texture, colour and odour give a general idea of the decomposition stage
reached and little information is gained as regards to the degree of maturation. For this
reason, chemical methods have been suggested, including measurement of the C:N ratio and
mineral N contents (Probert et al., 2005).
Conventional methods of composting animal excreta such as stockpiling raw excreta by the
side of cultivated field or the shed after scrapping it from shed floor results in nutrient losses,
and may lead to environmental pollution. It has been observed that during decomposition,
several gases such as CO2, methane, ammonia, nitrous oxide and hydrogen sulphide which
contribute to global warming are formed and volatilized (Eghball and Power, 1994). In
29
addition, the conventional methods of composting are costly in terms of time and labour,
especially when they involve turning or transferring the decomposing materials from pit to
pit (Zake et al., 2005). Some of the most valuable fertiliser nutrients, particularly N are lost
during composting (Lekasi et al., 2001). Martins and Dewes (1992) reported 77% gaseous N
losses during composting animal wastes, and turning the manure heaps accounted for 49% of
this total, probably by stimulating aerobic microbial activity and allowing better aeration. In
a study where the heap was not turned but the surface was in contact with the atmosphere,
denitrification losses were more important (Petersen et al., 1998).
Studies by Eghball (2000) on N mineralisation from non-composted and composted beef
cattle feedlot manure applied to no-till and conventional tillage systems showed that of the
organic N applied, twice as much N (21%) was mineralised from non-composted than from
composted manure (11%) during the first growing season after application. The lower N
mineralisation from composted manure was attributed to the loss of easily convertible N
compounds during composting process. Thus, this study seeks to develop less labour
intensive, low-cost technologies of composting animal faeces that are affordable to the
resource-limited smallholder farmers. This study also seeks to determine whether the faecal
storage methods under study, which do not involve transfer of composting faeces from pit to
pit affect the maturity period as well as the mineral content of the resultant manure composts.
30
2.8
Utilisation of livestock manure as a soil amendment in the crop-livestock
production systems
In order to ensure sustainability of the smallholder dairy farming in urban/peri-urban areas of
Uganda, there is need to maintain soil fertility and productivity by ensuring nutrient recycling
as one of the practices. Most soils have deteriorated in fertility leading to a decline in
quantity and quality of feed resources, incomes and food security of smallholder farmers
(Zake et al., 2003; Katuromunda et al., 2001; Mugisa et al., 1999). This has been attributed
to the fact that the rate at which nutrients are removed from soil is far greater than the rate at
which they are returned. This trend can be reversed through application of livestock manure
and supplementing it with mineral fertilisers in case its supply is insufficient.
Livestock manure is a valuable resource for smallholder farmers because of the nutrients it
contains, which are of great importance in sustaining soil fertility and productivity (Giller,
2002). It supplies both immediately and slowly released nutrients that are essential for crop
production. In addition, it provides organic matter that has positive effects on the physical
properties of soil notably, improving water retention capacity, nutrient exchange capacity,
soil structure and aggregate stability; regulating soil pH by acting as buffer and promoting
population growth of beneficial soil organisms (Kihanda and Gichuru, 1999; Karanja et al.,
1997; Harris et al., 1997; Mugwira and Murwira, 1997). Because of its buffer action on pH,
manure was reported to increase the levels of P in the soil available to crops, which in turn
led to an improvement in yields and quality of crops than when mineral fertiliser P was
applied at the same levels (Reddy et al., 2000). In contrast, prolonged application of mineral
fertilizers to tropical soils has been reported to cause acidification of soil and stagnation in
crop yields (ILRI, 1997). Bekunda et al. (1997) noted that due to economic reasons and
31
unavailability of mineral fertilizers, farmers do not apply them at appropriate rates which also
affect crop yields negatively.
However, livestock manure alone cannot generate large increases in crop production that are
needed to feed the ever-increasing human population in sub-Saharan Africa (Lal, 2001). The
quality and availability of livestock manure varies with diet of the animal and season of the
year, among other factors (Delve et al., 2001; Paul et al., 1998; Tomlinson et al., 1996;
Somda et al., 1995). In addition, the nutrients found in livestock manure cannot be
substituted for those in mineral fertilizers on an equal basis. The reason for this is that,
whereas the nutrients in mineral fertilizers are readily available for plant uptake following
application, those in manure are not all available to crops in the year of application. Some are
in their organic form and their availability depends on the rate of decomposition and release
from the organic components. According to Koelsch and Shapiro (1998), 70-80% of P and
80-90% of K in manure are available to crops in the first year after application. For the case
of N, the entire mineral N (NH4+ + NO3–) is potentially available to crops during the first year
after manure application. But the proportion of organic N converted to plant-available forms
within the first cropping year varies according to the manure handling system, among other
factors. Koelsch and Shapiro (1998) observed that 35, 25 and 14% of organic N is available
to the crop in the first year of application from dairy excreta without bedding, excreta mixed
with bedding and composted dairy manure, respectively.
32
Studies elsewhere have shown that when cattle manure and mineral fertilisers are applied
together in the field, they complement each other and the resultant improvement in crop
yields is greater than when they are applied separately (Kimani et al., 2004; Ahmed and
Sanders, 1998; Bationo et al., 1998). Studies of Kimani et al. (2004) indicated that
combining manures with mineral fertilisers was more effective in the production of maize,
compared to singular application of manure (5 ton ha-1) and mineral fertiliser (Di-ammonium
phosphate) alone applied at rates below 100 kg N ha-1. However, the effects of applying a
combination of composted cattle manure and mineral fertilisers on the agronomic
performance and nutritive quality of P. purpureum fodder have not yet been adequately
determined, and thus the focus of this study.
In summary, this review has indicated that urban/peri-urban agriculture is increasingly being
recognised as an important component of urban development and urban environmental
management. It can be a viable source of income, jobs and food for the urban poor. The
practitioners of urban/peri-urban agriculture enjoy better nutrition, higher income,
employment, an improved living environment and savings in energy as they use biogas.
However, the ever-rising demand for human food is putting tremendous pressure on the
available natural resources, especially soils, and is likely to cause more degradation of the
environment. Thus, the major challenge at hand is to develop environmentally sustainable
low-cost technologies that will optimize and sustain the productivity of these urban/periurban low-input smallholder farming systems.
33
The review indicated that soil nutrient depletion is a major constraint to obtaining optimum
grain and fodder yields in the urban/peri-urban areas. Smallholder farmers rarely apply
mineral fertilisers to maintain soil fertility due to several constraints, including limited
accessibility and high cost. These farmers keep dairy cattle which produce manure in
addition to milk. If this manure was well managed and recycled, it would contribute to the
sustenance of soil fertility and productivity in these areas. To enable farmers accurately plan
for the utilisation of this manure, there is need to quantify its amounts and also determine its
fertiliser quality. Also, in order to maximize its use efficiency as a soil amendment, there is
need to design better methods of manure collection and storage since these are some of the
critical stages of nutrient transfer through crop–livestock systems where efficiency of
nutrient cycling could be improved. Therefore, because of these reasons, it was worthwhile to
conduct research on manure use in urban/peri-urban intensive agricultural systems for the
benefit of the resource-poor smallholder farmers.
34
CHAPTER THREE
EXPERIMENTAL
3.1.0 EXPERIMENT 1: Improving the quality of diet and manure by supplementing
Pennisetum purpureum offered to lactating dairy cattle with legume foliage meal
3.1.1 Introduction
Ruminant livestock in the urban/peri-urban crop-livestock production systems depend mainly
on P. purpureum fodder because of its high biomass yield compared to other grasses
(Boonman, 1993; Kabirizi, 1996). However, its low levels of CP and metabolisable energy,
and high levels of neutral and acid detergent fibre render it incapable of providing sufficient
nutrition to lactating dairy cows thereby leading to severe reduction in animal productivity
(Saamanya, 1996). To improve its usage as livestock feed, supplementation with energy and
protein-rich feedstuffs is necessary. Supplementation of roughages with legume forages has
been proved to be a better option for the smallholder resource-poor farmers in the mixed
crop-livestock production systems (Mpairwe et al., 2003; Mwangi and Wambugu, 2003;
Kabirizi et al., 2000; Katuromunda et al., 2000). Legume forages have been identified as
economical, on-farm produced supplements alternative to commercial concentrates whose
availability and cost are quite limiting (Mugisa et al., 1999). Legume forages increase the
efficiency of utilisation of roughages by promoting voluntary feed intake and digestibility,
and by providing nutrients that are lacking in roughages, particularly crude protein.
35
Mpairwe et al (2003) established the optimum level of legume herbage supplementation that
maximizes feed intake and milk output in Friesian x Zebu crossbred dairy cows. However,
the consequent effect of optimising milk production in crossbred dairy cows using legume
meal on the output and mineral content (fertiliser value) of faeces excreted has not been
adequately explored. A lot of research on the production and characteristics of cattle manure
has been carried out in the semi-arid West Africa and temperate regions (Delve et al., 2001;
Van Kessel et al., 2000; Powers and Van Horn, 2001; Somda et al., 1995; Fernández-Rivera
et al., 1995). However, comparative data on the quantity and fertiliser value of manure
produced by dairy cattle reared in the urban/peri-urban farming systems whose diets are
supplemented with leguminous forages are inadequate. The estimates of quantities and
fertiliser value of livestock manures from semi-arid West Africa and temperate regions are
limited in their use by farmers in the East African region as they are based on different
breeds of cattle with different levels of production, rearing systems and diets. The objectives
of this study were to:
1. Determine the effect of legume supplementary feeding to dairy cows offered P.
purpureum basal diet on feed intake, milk yield, faecal output and faecal quality.
2. Develop regression models for predicting faecal output and the amounts of N and P
excreted in faeces by dairy cows offered P. purpureum basal diet and supplemented with
legume foliage meal.
36
3.1.2
Materials and methods
3.1.2.1
Experimental design and management
This study was conducted at Makerere University Agricultural Research Institute Kabanyolo
(MUARIK). The Institute is located 19 km north of Kampala at 00 28" N and 320 37" E, and
at an altitude of 1204 m above sea level. Four lactating Friesian (Bos taurus) x Zebu (Bos
indicus) crossbred dairy cows were used. This breed of cattle is the most popular within the
urban/peri-urban areas of Uganda. The cows were selected from a MUARIK dairy herd,
targeting those that were in early and almost same stage of lactation. Prior to commencement
of the experiment, their weights were taken using a heart girth tape measure and their mean
live weight was 50461 kg. This was repeated fortnightly until the experimental period was
over. The cows were housed individually in well-ventilated, concrete-floored stalls. Each
stall was equipped with a wooden feed trough and a water trough. Cows were dewormed
with Nilzan monthly and also sprayed with Delnav acaricide weekly to control worms and
ticks, respectively.
3.1.2.2
Diets and feeding management
Four treatment diets were offered to the lactating dairy cows in a 4 x 4 switchover Latin
square design (Appendix Table 1). This design was the most applicable, given the number of
lactating cows that were available for the experiment. It was difficult to get a bigger number
of dairy cows that were at the same stage of lactation. The diets comprised P. purpureum
fodder fed ad libitum (control), P. purpureum fed ad libitum + Calliandra meal, P.
purpureum fed ad libitum + Centrosema meal and P. purpureum fed ad libitum +
Desmodium legume meal. These legumes were found to be grown and used as feed
supplements by the majority of smallholder dairy farmers in the urban/peri-urban areas of
37
Uganda (Mugisa et al., 1999). The legume meal supplements were offered at 0.52% of the
animal body live weight, and constituted 20% of dry matter offered. Also, all the cows under
different dietary treatments received 2.68 kg DM (0.53% live body weight) of dairy meal
daily as additional supplement in order to ensure that the diets contained 11–13% CP for
moderate levels of milk production (ARC, 1980). At the commencement of the experiment,
the diets were assigned to the cows randomly.
Legume forages were harvested at the same time before commencement of the study, dried
under shed, ground to pass through a 3 mm sieve and kept in jute bags. This was done to
ensure that the chemical composition of legume meal fed to the animals was the same
throughout the experimental period. Pennisetum purpureum fodder was cut daily from the
field, chopped into 3-5 cm pieces and fed to the cows in fresh form. The feed troughs were
filled with chopped P. purpureum fodder three times a day at 07.30hrs, 12.00 noon and at
17.00hrs to ensure ad libitum supply to the cows. Dairy meal and legume meal were fed to
cows only in the morning and ensured that the amounts provided were all consumed before
filling the troughs with P. purpureum. Water troughs were filled with fresh clean water every
morning and made available throughout the day. The animals also had free access to
commercial mineral blocks. The experimental diets were maintained for a period of 28 days,
which included 14 days of adjustment to the diets and 14 days for data collection.
3.1.2.3
Sampling procedure and treatment of feed and faecal samples
500 g samples of feed (P. purpureum) and feed leftovers for each cow were collected daily
in the morning (07.30hrs) and evening (17.00hrs). In the evening, the two feed samples
collected for each cow were mixed thoroughly and sampled to obtain two 250 g sub-samples,
38
one for dry matter (DM) determination and the other for chemical analysis. The two leftover
samples for each cow collected daily were also sampled following the same procedure. In
addition, all the faeces excreted daily by each cow were scooped from the floor and kept in a
separate plastic bucket until the evening (17.00hrs) when weighing was done. After
weighing, the faeces for each cow were thoroughly mixed and two 250 gm sub-samples
taken. Contamination of faeces by urine was minimized by the floor being slanted so that
urine flowed away immediately it was passed out and scooping the faeces from the floor as
soon as they were defecated. The feed, leftover and faecal samples were then dried in the
oven at 60 0C for 72 hours, after which they were kept in the laboratory at room temperature.
After two weeks of sample collection, the oven dried sub-samples of feeds, leftovers and
faeces for each cow needed for chemical analysis were ground to pass through a 1-mm
sieve, bulked and sampled again after thorough mixing to obtain a final composite sample.
Dry samples of feeds, feed leftovers and faeces for DM determination were weighed and the
measurements obtained were used to calculate daily DM intake and faecal-DM excretion.
Daily dry matter intake was calculated as dietary DM offered minus dietary DM leftover.
3.1.2.4 Milk yields and composition
The animals were hand-milked twice a day, in the morning at 7.00 a.m. and in the afternoon
at 4.30 p.m. throughout the experimental period. Milk yield values were converted to 4 %
FCM yield and recorded. In the last week of each feeding period, milk samples of each cow
were taken daily in the morning and afternoon, bulked into one sample and analysed for the
butter fat content using Gerber method (British Standards Institute, 1989).
39
3.1.2.5
Chemical analysis of feed and faecal samples
Composite samples of feeds, feed leftovers and faeces were analysed to determine their
organic matter content by loss on ignition in a muffle furnace at 5500C; total N, P, Ca and K
using wet acid oxidation (Okalebo, 1985); neutral detergent fibre (NDF), acid detergent fibre
(ADF) and acid detergent lignin (ADL) by the Van Soest and Robertson (1985) method; total
soluble polyphenols by the Folin-Denis method (Constantinides and Fownes, 1994) and
neutral-detergent-insoluble nitrogen (NDF-N) by Ancom incubation followed by nitrogen
determination (Ancom Technology Corp., Fairport, USA; Van Soest et al., 1987). Calcium
and K were assayed using the flame photometer (Model PFP7, Jenway Co. Ltd), while P was
assayed using the colorimeter (Model CO 7000). The pH of faecal samples was determined
using a pH meter on a 1:1 by volume of water:faecal mixture.
3.1.2.6
Estimation of energy content
Gross energy of feeds (GEF) was determined by complete oxidation of the samples in
presence of oxygen in an adiabatic bomb calorimeter (AOAC, 1990). Metabolisable energy
(ME) of feeds was estimated from the digestibility of organic matter in the dry matter
(DOMD) using the expression, ME of feed = 0.15 DOMD% MJ kg-1DM (MAFF, 1987).
The %DOMD was determined using MAFF (1987) guidelines as follows:
%DOMD = (Feed OM – Faeces OM) x 100
Feed DM
The ME intakes of feeds were then calculated as follows:
ME intake (MJ head-1 day-1) = Dry matter intake (kg day-1) x ME of feed.
40
3.1.2.7
Statistical analysis of data
The data collected were subjected to analyses of variance procedure using the general linear
models of the Statistical Analysis Systems Institute (SAS, 2004) for a Latin square design
using the model outlined below.
Xijk
 + i + j + k + ijk;
=
i , j and k = 1 ......a
where, Xijk = the kth observation on the response variable under the ith treatment
 = Mean
 = Treatment effect

= Period effect
 = Animal effect
 = Random error effect
Differences between treatment means for the various parameters were delineated using the
least significant difference (LSD) and were considered significant at the 5% level (P<0.05).
41
3.1.3
Results
3.1.3.1
Chemical composition of experimental feeds and faeces
The concentrations of chemical components in feeds were not compared statistically because
the concentrations of chemical components in the legume meals did not vary from period to
period since they were harvested at once and dried under the sun. However by looking at the
differences, Calliandra and P. purpureum had the highest and lowest CP contents,
respectively compared to other feeds (Table 1).
Table 1.
Mean chemical composition of feeds fed to the lactating dairy cows at MUARIK
Experimental feeds
Component
P. purpureum
Dairy meal Calliandra
Centrosema Desmodium
g kg-1 DM
Organic matter
906.70
931.80
946.80
953.90
928.20
91.60
173.40
231.30
125.00
131.30
nd
nd
73.53
11.07
10.98
6.22
24.78
25.65
12.39
9.09
NDF
390.57
293.61
366.25
488.13
616.70
ADF
445.52
149.52
375.58
447.08
505.35
ADL
73.84
40.38
109.39
202.23
153.85
Phosphorus (P)
2.40
9.00
2.20
1.80
2.40
Potassium (K)
16.80
10.20
14.20
12.10
8.90
Calcium (Ca)
1.21
1.10
2.52
4.00
4.75
16.68
19.69
21.82
21.38
19.30
Crude protein (N x 6.25)
Polyphenols
NDF-N (g kg-1 NDF)
Minerals
Energy content (MJ kg-1 DM)
Gross energy
NDF = Neutral detergent fibre; NDF-N = Neutral-detergent-insoluble nitrogen; ADF = Acid
detergent fibre; ADL = Acid detergent lignin; nd = Not determined.
42
Calliandra had greater concentrations of polyphenols and fibre-bound nitrogen (NDF-N)
than Centrosema and Desmodium. The concentrations of NDF and ADF were greatest in
Desmodium and lowest in dairy meal. Centrosema and dairy meal had the highest and the
lowest ADL contents, respectively. Phosphorus content was greatest in dairy meal and lowest
in Centrosema, while K content was greatest in P. purpureum and lowest in Desmodium. Ca
content was highest in Desmodium and lowest in dairy meal.
With respect to the composition of faeces, the OM contents for all the diets were similar,
apart from that of Desmodium diet which was significantly lower (Table 2). Faecal-N was
significantly higher in the faeces which were excreted by cows fed Calliandra diet, while the
one of cows fed Desmodium diet was lower than that of the control. Cows which were fed on
the control and Desmodium supplemented diets excreted faeces with P contents that were
similar but superior to those excreted by cows fed on Calliandra and Centrosema
supplemented diets. Among the supplemented diets, faeces derived from Centrosema diet
had lower P content than those from Desmodium supplemented diet. There were no
differences in the contents of faecal-K and Ca for all the diets.
43
Table 2.
Mean chemical composition (quality) of faeces excreted by lactating dairy
cows fed on Pennisetum purpureum and different legume meal supplements
Dietary supplements
Component
Control diet
Calliandra
Centrosema
Desmodium
LSD(0.05)
g kg-1 DM
867.41a
867.68a
869.22a
865.10b
2.26
Faecal-N content
15.97b
17.66a
15.64bc
15.37c
0.43
Faecal-P content
9.11a
8.21b
7.45c
9.12a
0.58
Faecal-K content
15.92
16.56
16.04
17.60
1.97
Faecal-Ca content
2.64
2.56
2.58
2.62
0.08
698.91a
676.80c
684.66bc
691.32ab
11.77
12.15a
12.61a
10.62b
10.11b
0.95
c
b
416.59
c
471.52
a
19.01
123.43
125.09
7.95
Organic matter
NDF
NDF-N (g kg-1 NDF)
ADF
403.70
ADL
126.54
437.99
125.45
ab
Means within a row followed by different superscripts differ (P<0.05); LSD = Least Significant
Difference
With the exception of Desmodium diet, faeces from legume meal supplemented diets
contained lower amounts of NDF than the control. The faecal- NDF content of Calliandra
diet was lower than that of Desmodium diet. Faeces derived from Centrosema and
Desmodium diets contained lower amounts of NDF-N than those from the control and
Calliandra diets. The ADF contents were lower in the control and Centrosema diets. Among
the legume meal supplemented diets, faecal-ADF increased in the order Centrosema <
Calliandra < Desmodium. There were no significant differences among the faecal
concentrations of ADL for all the treatments.
44
3.1.3.2
Feed intake and digestibility, and faecal output
Feed intake, as indicated by total DMI and OMI, was significantly increased by the legume
meal supplements (Table 3). There were no differences between total DMI among the
supplemented treatments. Total OMI for the Calliandra supplemented diet was similar to that
of Centrosema diet, but higher than that of Desmodium diet. The apparent dry matter
digestibilities (ADMD), digestibilities of organic matter in dry matter (DOMD), ME of feed
and ME intake were similar for the legume supplemented diets but higher than those for the
control.
Faecal-DM and OM excretions were significantly increased by Calliandra and Centrosema,
and not by Desmodium. Faecal-DM excretion for the Calliandra diet was similar to that for
Centrosema diet, but was significantly higher than that for Desmodium supplemented diet.
Given the mean live weight of cows used in this experiment as 50461 kg and the mean
faecal-DM excreted as 4.60, the percentage daily faecal-DM excretion in relation to body
live weight was 0.91%. When expressed as percentage of DM intake, the quantities of faecalDM excreted averaged 32.7% of total DM intake.
45
Table 3.
Mean daily DM and OM intake, digestibility, milk yield and faecal excretion
by lactating cows fed Pennisetum purpureum and different legume meal supplements
Dietary supplements
Component
Control
Calliandra
Centrosema Desmodium
LSD(0.05)
Dry matter intake (DMI)
8.96b
9.73a
9.55ab
9.40ab
0.62
Dairy meal
2.68
2.68
2.68
2.68
----
Legume meal supplement
-----
2.68
2.65
2.66
----
Total DMI (kg cow-1 day-1)
11.64b
15.09a
14.88a
14.74a
0.62
Total DMI (g kg-1 LW day-1)
24.26b
30.78a
30.41a
29.57a
1.28
Total OMI (g kg-1 LW day-1)
22.09c
28.22a
27.92ab
27.02b
1.16
ADMD
624.38b
673.74a
677.90a
695.79a
31.28
DOMD
642.54b
691.30a
694.97a
712.26a
30.01
9.64b
10.37a
10.42a
10.68a
0.45
113.02b
157.20a
155.82a
157.99a
10.44
Basal feed (P. purpureum)
Digestibility (g kg-1)
Metabolisable energy
ME of feed (MJ kg-1 DM)
ME intake (MJ head-1 day-1)
Milk yield
Milk yield (kg day-1)
8.5b
10.0a
10.5a
10.0a
2.15
FCM yield (kg day-1)
8.0b
10.0a
10.3a
10.0a
2.13
Faecal excretion (kg cow-1 day-1)
DM
4.32c
4.87a
4.75ab
4.46bc
0.32
OM
3.74c
4.22a
4.12ab
3.85bc
0.28
ab
Means within the same row having different superscripts are significantly (P<0.05) different;
ADMD = apparent dry matter digestibility; DOMD = digestibility of organic matter in dry matter;
LW = live weight; LSD = Least Significant Difference.
46
3.1.3.3
Nutrient intake and excretion in faeces
Supplementation with legume meal significantly (P<0.05) increased the daily intake of
nutrients as compared to the control diet (Table 4). Cows which were supplemented with
Calliandra consumed and also excreted larger amounts of N than cows supplemented with
either Centrosema or Desmodium. On average, 36.2% of the N consumed was excreted in
faeces and varied between 31.8 and 44.8% for the Desmodium supplemented diet and the
control. Among the supplemented diets, daily K intake was higher for the Calliandra and
Centrosema diets, while Ca intake varied in the order Calliandra < Centrosema <
Desmodium.
The amounts of P excreted in faeces were greater for cows supplemented with Calliandra. A
large proportion of P (53-63%) which was consumed by the cows was later excreted in
faeces. Faecal-K excretion was significantly higher for the Calliandra supplemented diet,
intermediate for the control and Centrosema diets, and lower for Desmodium diet. Higher
amounts of Ca were excreted in faeces by cows fed Calliandra and Centrosema. The
proportions of Ca excreted varied from 49 to 107% for the Desmodium supplemented and
control diets, respectively. Cows maintained on the control diet excreted higher proportions
of Ca than those supplemented with legume meal. Among the supplemented diets, the
proportions of Ca excreted varied in the order Desmodium < Centrosema < Calliandra.
47
Table 4.
Daily N, P, K and Ca intake and excretion by lactating dairy cows fed Pennisetum purpureum and different legume
meal supplements
Dietary supplements
Nutrient
LSD(0.05)
Control diet
Calliandra
Centrosema
Desmodium
Total N intake (g kg-1 LW day-1)
0.322c
0.536a
0.433b
0.433b
0.012
Faecal-N content (g kg-1 LW day-1)
0.141bc
0.176a
0.150b
0.139c
0.011
Faecal-N as percent of N intake
44.8
33.4
34.9
31.8
-----
Total P intake (g kg-1 LW day-1)
0.093b
0.106a
0.102a
0.105a
0.004
Faecal-P content (g kg-1 LW day-1)
0.057b
0.063a
0.055b
0.054b
0.006
Faecal-P as percent of P intake
63.2
60.4
55.7
53.0
-----
Total K intake (g kg-1 LW day-1)
0.371c
0.469a
0.455a
0.415b
0.023
Faecal-K content (g kg-1 LW day-1)
0.141b
0.185a
0.150b
0.127c
0.010
Faecal-K as percent of K intake
40.3
42.9
35.9
31.3
-----
Total Ca intake (g kg-1 LW day-1)
0.021d
0.035c
0.043b
0.046a
0.001
Faecal-Ca content (g kg-1 LW day-1)
0.022b
0.025a
0.026a
0.023b
0.002
Faecal-Ca as percent of Ca intake
107.1
70.0
60.4
49.3
-----
abc
Means within same row having different superscripts are significantly (P<0.05) different; LW = live weight; LSD = Least Significant Difference
48
3.1.3.4
Prediction of faecal output (FO) and the quantities of N and P excreted in faeces
Prediction equations for the quantities of faeces excreted daily by crossbred dairy cows based
on linear terms for daily DMI and ADMD were developed using data from daily individual
cow measurements. When the body weight of cows and fat corrected milk (FCM) yield were
included in the regression model as independent variables, they were not significant and thus
were dropped. The equations developed were:
FO (g kg-1 LW day-1) = 17.36 + 0.32 x DMI (g kg-1 LW day-1) – 0.03 x ADMD (g kg-1); R2 = 0.96***... [1]
FO (kg day-1) = 8.46 + 0.31 x DMI (kg day-1) – 0.12 x ADMD (g kg-1); R2 = 0.95***….......………. [2]
The prediction equations were highly significant (p<0.0001). The absolute correlation
coefficient (R values) for both equations (0.98) was very high, suggesting that faecal output
was strongly related to DM intake and ADMD. The coefficients of determination (R2 values)
were also very high, indicating that these regression equations explained a considerable
proportion of the variations between faecal output and the two independent variables (DM
intake and ADMD).
Bi-variate regression analysis of daily faecal output per unit live body weight on ADMD
showed that a highly significant negative (p<0.0001) relationship exists between daily faecal
output and ADMD (Fig. 1). There was a consistent decline in faecal output with increasing
ADMD. The equation for the regression line obtained was: FO(g
kg-1 LW day-1)
= 20.95 –
0.0173*ADMD. The absolute correlation coefficient between faecal output and ADMD (R
value) was 0.698, suggesting that the two variables were strongly related. The coefficient of
determination (R2 value) obtained in the regression (0.487) was high. This indicates that the
49
regression equation explained a considerable proportion of the variations between faecal
output and ADMD.
16
y = -0.0173x + 20.95; R2 = 0.487
p<0.0001
12
-1
Faecal output (g kg LW day
-1
14
10
8
6
4
300
400
500
600
700
800
Apparent dry matter digestibility (g kg-1 )
Fig. 1: Linear regression of faecal output of crossbred dairy cows fed P. purpureum
diet and different legume meal supplements on apparent dry matter digestibility
50
A prediction equation for daily excretion of N in faeces based on the intake of DM and N
was also developed using data from daily individual cow measurements. The prediction
equation developed was:
Faecal-N (g day-1) = 85.58 + 0.39 x N intake (g day-1) – 6.63 x DM intake (kg day-1); R2 = 0.65*** [3]
This prediction equation was highly significant (p<0.0001). The body weight and FCM yield
were not significant components of the prediction equation, because when added in the
regression model they did not account for appreciable additional variation. The only
significant terms in the equation were linear terms for N intake and DM intake. The R value
was 0.806, suggesting that faecal-N was strongly related to N intake and DM intake. The R2
value obtained in the regression (0.65) was high, indicating that the regression equation
explained a considerable proportion of the variations between faecal-N and the intake of N
and DM.
A prediction equation for quantities of P excreted daily in faeces by crossbred dairy cows
was also developed using linear terms for daily P intake (PI), DM intake and ADMD. The
equation developed was:
Faecal-P (g day-1) = 58.71 – 0.41 x PI (g day-1) – 0.77 x ADMD (g kg-1) + 2.97 x DMI (kg day-1)
R2 = 0.423***……………………………………………………..………………………... [4]
The plot of studentized residuals versus the predicted values showed that this model provides
a good fit and does not violate any model assumptions. When FCM yield was included in the
regression model as an independent variable, it was significant (P<0.05) but did not account
for appreciable additional variation in the equation. Removal of either P intake or DM intake
from the regression model caused significant reduction in the R2 value of the prediction
equation.
51
3.1.4
Discussion
3.1.4.1
Chemical composition (nutrient content) of experimental feeds and faeces
The experimental feeds provided varying concentrations of N, polyphenols, fibre fractions
(NDF and ADF) and minerals to the dairy cows. Pennisetum purpureum had low levels of
CP and thus was a low quality feed. Its CP content (9.16%) was lower than the minimum
level (11-16%) required for maintenance and production of dairy cattle (NRC, 2001). If not
supplemented, it would result in depressed voluntary feed intake and digestibility (Tolera and
Sundstøl, 2000). The legume forages that were used in this study as supplements provided
the N, which was low in P. purpureum (Kaitho and Kariuki, 1997).
Higher concentrations of N in faeces excreted by cows supplemented with Calliandra were
due to high amounts of polyphenols which are known to bind and protect proteins and
carbohydrates from degradation in the digestive tract at rumen pH (Reed, 2001). Also,
nutrient levels in manure can vary considerably depending upon the composition of diet fed
to the animals, among other factors. van der Stelt et al. (2008), Weiss and Wyatt (2004),
Delve et al. (2001), Paul et al. (1998), Tomlinson et al. (1996), Somda et al. (1995) and
Morse et al. (1992) reported that feeding diets containing nutrients in excess of animal
requirements leads to their increased excretion. The Calliandra supplemented diet contained
the highest amount of CP, and therefore, this could have also contributed to excretion of
higher amounts of N by cows maintained on this diet. van der Stelt et al. (2008) studied the
effects of various dietary protein and energy levels on manure composition (Ca, Mg, K, Na,
N, P, and pH) and observed that increasing the dietary CP content from 108 to 190 g kg-1 DM
resulted in an average increase in total N and P content of the slurries by 56 and 48%,
respectively. Also, feeding the cows more energy (5,050 to 6,840 kJ kg-1 DM) increased total
52
N and P content of the slurries by 27 and 39%, respectively. Tomlinson et al. (1996)
observed that as the dietary CP increased, the concentrations of total solids and volatile solids
also increased. Since the excreted nutrients are a component of excreted solids, an increase in
the excretion solids would certainly lead to an increase in the excretion of nutrients.
3.1.4.2
Feed intake and digestibility, and faecal output
The increased total DM and OM intakes and digestibility (ADMD and DOMD) with legume
supplementation was attributed to higher crude protein (N) content that was availed to the
rumen microbes by the protein-rich legume meal (Ebong et al., 1999). When supplied with
sufficient amounts of N, the rumen microbes increased, thus enabling them to speed up the
rates of DM and OM degradation and clearance from the rumen (Silva and Orskov, 1988).
Higher rates of feed degradation and clearance from the rumen created room for more feed to
be consumed (Abule et al., 1995; Umunna et al., 1995). The increase in feed consumption
and rate of passage through the rumen, in turn lead to higher faecal excretion in the
Calliandra and Centrosema supplemented diets. The ME intake for all treatments was above
the minimum (95 MJ head-1 day-1) level recommended for growth and production of lactating
dairy cattle by NRC (2001). The significant increase in ME intake with legume
supplementation was attributed to higher OM intake as well as higher ME contents in the
legume meal as compared to the P. purpureum (Mpairwe et al., 2003).
3.1.4.3
Nutrient intake and excretion in faeces
Excretion of larger amounts of N observed in the Calliandra supplemented diet was due to
the high concentrations of N and polyphenols in Calliandra. Lekasi and Kimani (2003)
observed that the amount of N excreted in faeces was highly influenced by the N contents of
53
the feeds; and the higher the amount of N in the diet, the more that was excreted in faeces.
Paul et al. (1998) also observed that the concentration of N was lower in the manure obtained
from dairy cattle fed diets lower in N, and attributed this to efficient utilisation of N in the
diet by the animal. In addition, Calliandra like other browse plants contains high levels of
polyphenols and tannins (Bareeba and Aluma, 2000). These compounds form complexes
with CP in feeds and as a result reduce protein digestibility, which in turn leads to increased
excretion of N in faeces (Delve et al., 2001; Maasdorp et al., 1999; Somda et al., 1995).
Higher intake of P, K and Ca in the supplemented diets was attributed to the additional
amounts of the nutrients that were supplied by the legume meal. A large proportion of P
consumed by the cows on all the diets was excreted in faeces because P is excreted almost
exclusively in faeces (Powell et al., 1994). In addition, some of the P excreted comes from
endogenous sources, and was estimated as 0.8 g/kg of DM intake (NRC, 2001). Dairy cows
that were maintained on the control diet excreted more Ca than they consumed. Animal
responses are influenced by the Ca:P ratio, such that exclusive feeding of one or the other
causes problems. The recommended ratio for lactating dairy cattle is 1-2:1 (MAFF, 1987). In
all the treatments, the Ca:P ratios were very low ranging between 0.22:1 and 0.44:1 for the
control diet and the Desmodium supplemented diet, respectively. The low concentrations of
Ca in the diets compared to those of P caused an imbalance in the absorption of Ca from the
digestive tract. Therefore, the concentrations of Ca in the diets used in this study were below
the animal requirements and needed to be supplemented.
54
3.1.4.4
Prediction of the amounts of faeces excreted
Prediction equations [1] and [2] indicate that basing the faecal output and DM intake either
on grams per unit body live weight or kilograms per day would still give a precise estimation
of faecal output, since the R2 values are almost the same. However, equation [1] would be
most applicable because the body weights of animals vary, and so does the DM intake. Since
urban and peri-urban farmers keep a few dairy cows, equation [1] gives them an opportunity
to estimate the faecal output of each cow basing on body weight. Faecal-DM output is an
inverse function of the ADMD. Therefore, knowing the digestibility of the dietary-DM and
the quantity of feed consumed would permit accurate estimation of the amount of DM
excreted. Powers and Van Horn (2001); Kyvsgaard et al. (2000) and Fernández-Rivera et al.
(1995) noted that ADMD is the best single independent variable for predicting faecal output.
Because of the negative relationship, highly digestible diets would result in reduced faecal
output, since apparent digestibility is the difference between the amount consumed and
amount collected in faeces. However, it was a reverse with the legume meal supplemented
diets due to the fact that increased feed digestibility as a result of supplementation, which in
turn would have led to a drop in faecal output, was counteracted by an increase in feed intake
and faster feed passage through the digestive tract.
3.1.4.5
Prediction of the amounts of N and P excreted in faeces
The excretion of N in faeces by crossbred dairy cows was predictable from DM and N
intakes. The equation that was developed for predicting faecal-N was similar to that
developed by Tomlinson et al. (1996), except that in this study the DM intake component
was negative. This was attributed to differences in the chemical composition of feeds that
were used in both experiments. In this study, the body weight of cows and FCM yield were
55
not significant factors in determining the excretion of N in faeces. Briceno et al. (1987)
reported that DM intake and milk yield of lactating cows are highly correlated. This explains
why it was possible to exclude milk yield from the regression model and remain with DM
and N intakes as the only components of the prediction equation that best fit the data from
this experiment. Other researchers, notably Tomlinson et al. (1996), observed that apart from
being significant in the equations for predicting urinary-N, the body weight of dairy cows
was not a significant component in the equations for predicting faecal-N.
The present study showed that excretion of P in faeces is a function of P intake, DM intake
and ADMD of the diet offered. Faecal excretion of P was negatively related to ADMD,
which suggests that as the digestibility of the diet offered increases, the excretion of P by
dairy cows decreases. However, the addition of both P intake and DM intake in the
regression model made the relationship between faecal P and intake of P negative. This was
due to the fact that intake of P incorporates both DM intake and dietary P concentration
(Weiss and Wyatt, 2004).
3.1.4.6
Implications of increased faecal and nutrient excretion
Faecal excretion is an unavoidable component of dairy production and a potential threat to
the environment if not properly managed (Harvey, 1989). In the recent past, feeding
strategies for dairy cattle have targeted maximising milk output without minding about the
subsequent increase in the output of animal excreta (Juma et al., 2006; Mpairwe et al., 2003).
However, as the faecal output increases as a result of increasing animal numbers as well as
supplementation with legume meal, its management becomes critical for environmental
56
sustainability (Alocilja, 1998). According to Kibombo (2007), the exotic and crossbred dairy
cattle population in Kampala district is estimated to be 3550 head of cattle, and are kept
under stall-feeding system. Assuming that each of these cows weighs 504 kg LW on average,
consumes 9.4, 2.7 and 2.7 kg DM of P. purpureum, dairy meal and legume meal,
respectively, and that all faeces excreted are collected and conserved, the computed
quantities of faeces and faecal components of these cows are presented in Table 5.
Table 5.
Mean faecal output and composition for a 504 kg crossbred dairy cow fed on
Pennisetum purpureum fodder supplemented with dairy meal and legume mealβ
Faecal-DM
Faecal-OM Faecal-N Faecal-P Faecal-K
Daily output (kg cow-1 day-1)
4.60
3.98
0.076
0.029
0.076
Annual output (kg cow-1 yr-1)
1,679
1,453
28
11
28
Annual output for 3550 cows
of 504 kg mean LW (Tons yr-1)
5,960
5,157
98
38
98
Quantities recovered under
3,576
3,094
59
30
78
efficient conservation (Tons yr-1)
βAmounts
consumed were 9.4, 2.7 and 2.7 kg DM of P. purpureum, dairy meal and legume meal
(Calliandra, Centrosema or Desmodium), respectively
If all these faecal components are transported by rain water annually to the water bodies,
such as Lake Victoria, eutrophication is likely to increase (Woomer et al., 1998). However,
this can be avoided by efficiently collecting, conserving and utilizing animal excreta as biofertiliser resource which can contribute to the sustenance of crop/fodder production in the
urban/peri-urban crop-livestock production systems. Eghball and Powers (1994) and Eghball
et al. (1997) reported that depending upon how the manure is handled, as much as 50% of the
57
N excreted by stall-fed cattle is lost through runoff and volatilization by the time it is ready
for application in the field. Powers and Van Horn (2001) noted that whereas losses of P and
K from manure are quite small, losses of N to the atmosphere are unavoidable, at least 35%
of excreted N in best case scenarios and 60% or more, in most situations. Thus, assuming
that efficient collection and conservation of animal excreta permitted 60% recovery of the N
and 80% of the P and K excreted daily in faeces, the annual recovery of N and P would be 59
and 30 ton, respectively (Table 5). Although these quantities may appear small, they are still
significant given the small farm sizes owned by the majority of urban/peri-urban smallholder
farmers and affordability of mineral fertilisers.
58
3.2.0 EXPERIMENT 2: Physical and chemical characteristics of composted cattle
manures as influenced by faecal storage method
3.2.1 Introduction
The growing dairy cattle population in the urban/peri-urban areas coupled with improvement
in feeding is generating more manure as shown in experiment 1 – a waste product, which if
well managed can become an input to other production enterprises, such as biogas and
crop/fodder production. Dairy cattle reared in Kampala District are kept in stalls and the
excreta are scrapped off the floor of the stall daily and stockpiled on bare ground by the side
of the stall, from where it is later transported to the fields. When left exposed to the
atmosphere, nutrients in the excreta are lost through volatilization (especially N), runoff and
leaching (Eghball et al., 1997). As a result small quantities of nutrients are potentially
recyclable through manure within the farm system.
Making the most efficient use of livestock manures depends critically on improving manure
handling and storage. In their review on nitrogen cycling, Rufino et al. (2006) observed that
most publications on organic matter transfer and utilisation centred on the livestock and soil–
crop sub-systems, and there was a distinct lack of information regarding manure handling
and storage to maintain its quality. In order to maintain the consistency of livestock manure
quality as presented in experiment 1, it is important to design efficient management strategies
that address nutrient losses during manure handling and storage. In this regard, therefore, this
study was intended to identify the most effective method of storing cattle faeces which will
lead to production of compost with better manuring quality.
59
3.2.2 Materials and methods
3.2.2.1
Experimental design and management
This experiment conducted at MUARIK was a two factor randomised complete block design
comprising four types of faeces excreted by dairy cows and four methods of faecal storage.
The treatments were replicated four times. The treatment diets and feeding management were
as explained in experiment 1, and faeces produced were the ones used in this experiment. All
the faeces excreted daily by each cow on a particular diet were scooped from the floor,
weighed and then stored in separate closed metallic drums. Storage of faeces in the drum was
intended to minimize exposure to the atmospheric conditions that would lead to nutrient
losses through volatilization, runoff and leaching by rainfall. After two weeks of collection,
the faeces of each cow were emptied from drums on to a concrete floor, mixed thoroughly
using a spade and a 500g sample was taken. After sampling, faeces of each cow were divided
into four equal portions and then subjected to four storage methods over a three months
period. During the experimental period, daily maximum temperature and rainfall were
recorded (Appendix Fig. 1). The four storage methods were:
(i)
Placing faeces in pits (0.75 m deep and 0.75 m diameter) and covering with a layer of
soil 2.5 cm thick. Dry grass was placed over the faeces to avoid contamination by soil
(T1),
(ii)
Placing faeces in pits lined with polythene paper and then covering with another sheet
of polythene (T2),
(iii) Placing faeces in pits and leaving the pits open (T3), and
(iv) Stockpiling the faeces on flat ground and leaving them uncovered (Control) (T4).
60
These storage methods were designed to reflect the potential and farmers’ conventional
methods of storing cattle manure in the urban/peri-urban areas of Uganda. The majority of
smallholder dairy farmers stockpile cattle excreta in the open just adjacent to the stall (T4
method). Covered versus uncovered treatments were used to capture the effects of
precipitation and solar heating.
3.2.2.2
Sampling procedure and treatment of manure samples
After three months of storage, the faeces henceforth referred to as composted cattle manure
were sampled. The covered pits were opened up and the top layer of manure scrapped off.
Sampling of the manure in each pit consisted of taking circular core samples from four
different locations of the pit from top to the bottom using a 6 cm diameter plastic tube. The
four core samples were then mixed thoroughly and a 500g sample was taken and placed in a
black polythene bag. For the case of faeces that were stockpiled on flat ground, samples were
collected from different points on the heap after scrapping off the top layer, mixed
thoroughly and a 500g sample taken. In addition, the texture, colour, smell and biological
activity of samples were assessed following procedures used by Lekasi et al. (2003a) to
judge the maturity and quality of the composted cattle manures.
3.2.2.3
Chemical analyses of manure samples
Samples that were taken before subjecting cattle faeces to storage treatments (faecal samples)
and those of composted cattle manure were analyzed using the procedures as in experiment 1
(Section 3.1.2.4) for OM, total N, P, K and pH. The NH4-N content was determined by
adding 2 g of MgO to 2 g of wet manure before distillation of NH4-N fraction using an
automatic Kjeldahl system (Tecator Kjeltec Auto).
61
3.2.2.4
Statistical analysis of data
The data from faecal and composted manure samples were used to determine the changes in
the concentrations of OM, total N, P and K, and pH as affected by legume supplementary
feeding (Appendix Tables 2 – 6) and by faecal storage treatments (Appendix Tables 7 – 11).
The data were then subjected to analyses of variance procedure for a randomised complete
block design using the Statistical Analysis Systems Institute (SAS, 2004) and following the
model outlined below.
Xij
where,
=
 + i + j + ij + ij;
i and j = 1 ......a
Xij = the jth observation on the response variable under the ith treatment
 = Mean
 = Dietary treatment effect
 = Faecal storage treatment effect
 = Interaction between dietary and faecal storage treatment effects
 = Random error effect
The concentrations of N, P, K and pH at the start of the incubation were used as covariates in
the statistical analyses. Differences between means for the various parameters were
compared using the least significant difference (LSD) at the probability level of 5%.
62
3.2.3
Results
3.2.3.1
Physical properties of composted cattle manures
The compost derived from faeces which were stored in pits and covered with soil (T1) had a
fairly coarse texture and mottled appearance (Table 6). The outer layers were at advanced
stages of decomposition than the layers inside the pile. Faeces that were wrapped in
polythene sheet and stored in pits (T2) had not changed in appearance, texture and smell. The
compost derived from faeces which were stored in open pits (T3) and that from faeces
stockpiled on flat ground and left uncovered (T4) were at advanced stages of decomposition
and exhibited features of maturity, namely fine texture, homogeneous colour, inoffensive
smell and presence of macroorganisms.
63
Table 6.
Physical properties of the composted cattle manures that were sensually evaluated
Faecal storage method
Texture
Colour
Odour
Biological activity
Faeces stored in pits and
Fairly coarse textured.
Mottled appearance
Smell of putrefaction
Not yet invaded by
covered with soil (T1)
Faeces at various stages of
with colours ranging
indicating that
any macrofauna
decomposition covering
from that of fresh
decomposition was
fresh faeces in the centre
faeces to dark brown
occurring
Wrapped in polythene sheet
Coarse textured material
Colour of fresh faeces
Strong smell of
Not yet invaded by
and stored in pits (T2)
that looked like fresh
with no visible sign of
ammonia which is
any macrofauna
animal faeces.
decomposition taking
characteristic of fresh
place
animal faeces
Stored in pits and left
Fine textured and at an
A homogeneous
A mild and
Earthworms,
uncovered (T3)
advanced stage of
material, with uniform
inoffensive smell like
beetles and termite
decomposition
black colour.
that of soil.
tunnels present
Stockpiled on flat ground and
Fine textured and at an
A homogeneous
A mild and
Many earthworms,
left uncovered (T4)
advanced stage of
material, with uniform
inoffensive smell like
beetles, tunnels of
decomposition
black colour.
that of soil.
termites observed.
64
3.2.3.2 The ammonium concentrations, C:N ratios and changes in the chemical
properties of composted cattle manures
The interaction between the effect of supplementing P. purpureum diet with legume foliage
and the effect of faecal storage methods did not significantly (P>0.05) influence any of the
parameters that were measured. The NH4-N concentrations and C:N ratios were treated
independently of the other chemical properties because, this study aimed at determining the
treatment(s) where these two would decline to the lowest levels. This is one way of
determining the maturity of the resultant compost(s) as was reported by Probert et al. (2005)
and Zucconi and de Bertoldi (1987). Supplementation of P. purpureum diet with legume
foliage meal did not have a significant effect on C:N ratios and on the concentrations of NH4N in the composted cattle manures (Table 7; Appendix Table 12). Apart from the
concentration of N in the compost derived from faeces excreted by cows supplemented with
Calliandra, the concentrations of N, P and K in all the other composts declined. Nitrogen
losses from composts obtained from Centrosema supplemented diet were similar to those of
the control but higher than that of the compost Calliandra supplemented diet.
Losses of P in the composts derived from faeces excreted by cows on legume supplemented
diets did not differ from that obtained from faeces of cows fed on the control diet. Among the
supplemented diets, loss of P was greatest in the compost obtained from faeces of cows
supplemented with Centrosema compared with the compost obtained from faeces of cows
fed Calliandra. On average, P losses varied between 49.6 and 57.4% of the initial amounts.
65
Table 7.
The ammonium concentrations, C:N ratios and changes in the chemical
properties of composted cattle manures as affected by legume supplementary feeding
to dairy cattle offered Pennisetum purpureum
NH4-N
content
(g kg-1)
C:N
ratio
OM
Calliandra calothyrsus
0.48
26.4
-60.93
+0.18c
-3.01b
-9.75b
+1.7
Centrosema pubescens
0.44
28.2
-99.63
-1.39ab
-3.96a
-7.51bc
+1.3
Desmodium intortum
0.48
29.1
-73.71
-0.05bc
-3.39ab
-6.20c
+2.0
Control
0.53
28.6
-107.55
-1.80a
-3.61ab
-13.72a
+1.7
LSD(0.05)
0.13
4.4
56.55
1.44
2.36
----
Legume meal
supplements
Total N
Total P Total K
change (g kg-1)
0.69
pH
rise
abc
Means within the same column having different superscripts are significantly (P<0.05) different;
LSD = Least Significant Difference.
Losses of K ranged from 29.5 to 55.7% of the initial amounts, with the highest loss occurring
in the compost derived from faeces of cows fed on the control diet (Table 7). Similar K
losses occurred in composts derived from faeces of cows whose diet was supplemented with
Desmodium and Centrosema, but these losses were lower than that of the compost obtained
from faeces of cows fed on the control diet. No differences were observed in the amounts of
K lost from composts derived from faeces of cows supplemented with Calliandra and
Centrosema. There was a general increase in the pH values of composts when compared with
the pH of faeces before subjection to the storage treatments.
The faecal storage methods significantly affected the ammonium concentrations and C:N
ratios and also caused significant changes in the chemical attributes of the composted cattle
manures (Table 8). The concentration of NH4-N in the compost obtained from T2 was higher
66
than those in the composts derived from other storage methods. The C:N ratios of composts
derived from T3 and T4 storage methods were similar, but that of the compost derived from
T3 was lower than those of composts derived from T1 and T2. The reduction in OM contents
from composts obtained from T3 and T4 storage methods were greater than that of T2. With
the exception of the compost derived from faeces subjected to T3 whose N content increased
by 7.4%, the concentrations of N in the composts derived from faeces which were subjected
to other storage methods declined. The decline in P concentrations was greater in composts
obtained from faeces subjected to T1 and T2 storage methods, while the decline in the
concentration of K was greater in the compost derived from faeces which were subjected to
T4 method (Table 8).
Table 8.
The ammonium concentrations, C:N ratios and changes in the chemical
properties of composted cattle manures as affected by faecal storage methods
Faecal storage methods NH4-N
content
(g kg-1)
C:N
ratio
OM
Total N Total P
change (g kg-1)
Total K
pH
rise
Pit and soil cover (T1)
0.40b
30.5a
-79.53ab
-1.62a
-4.25a
-9.10b
+1.8
Pit and polythene (T2)
0.76a
29.5a
-38.23b
-1.10a
-3.75a
-6.84b
+1.7
Pit and not covered (T3)
0.34b
24.4b
-100.54a
‡
1.08b
-3.03b
-8.28b
+1.6
Piled on flat ground (T4)
0.43b
28.0ab
-123.53a
-1.43a
-2.95b
-12.95a
+1.6
LSD(0.05)
0.13
4.4
56.55
1.44
0.69
2.36
----
ab
Means within the same column having different superscripts are significantly (P<0.05) different;
LSD = Least Significant Difference; ‡Signifies an increase.
67
3.2.4
Discussion
3.2.4.1
Physical properties of the composted cattle manures
Changes that occur in the physical properties of cattle manure during storage and are easily
recognizable using the senses of touch, sight and smell (particularly the texture, colour,
biological activity and odour) can be used to predict the maturity and quality of composts
(Lekasi et al., 2003a; Thorne and Tanner, 2002). During storage, decomposition gradually
transforms the coarse textured organic materials into a fine, loamy material called compost.
Therefore, by carefully using the sense of touch a farmer can tell whether or not the compost
material is ready for use as soil amendment. In this regard, therefore, the composts obtained
from faeces stored in open pits (T3) and those that were stockpiled on flat ground and left
uncovered (T4) were mature.
Changes in the colour of compost can also be used to determine its maturity. Cattle faeces
that are not fully decomposed consist of a more heterogeneous mixture with a mottled
appearance. This was observed in the compost derived from faeces stored in pits and covered
with soil (T1). Mottling was attributed to the fact that the outer layers decomposed at a faster
rate than those inside the pile. The whole faecal mass had not fully decomposed, and thus
required more storage time to decompose and turn into mature compost with a more
homogeneous dark brown or black colour. The composts derived from faeces stored in open
pits (T3) and those that were stockpiled on flat ground and left uncovered (T4) had turned
into a uniform black colour indicating that they had reached maturity.
68
Fresh animal manure and other organic wastes usually emit a strong smell of ammonia and
putrefaction during the early stages of decomposition. Also, when there is shortage of
oxygen, the composting process shifts from aerobic to anaerobic decomposition which is
slow and releases foul odours due to formation of sulphur compounds (Cooperband, 2002;
Thomsen, 2000). At maturity, the resultant compost has a mild and inoffensive smell like that
of soil, which is attributed to the presence of humic substances (Bernal et al., 1998).
Therefore, the composts that were obtained from faeces subjected to T1 and T2 storage
methods whose smell was offensive had not matured, while those obtained from faeces
subjected to T3 and T4 storage methods had reached maturity.
The invasion of decomposing cattle faeces by macroorganisms also serves as an indicator of
compost maturity. The OM in fresh animal excreta is decomposed by the successive action of
bacteria, fungi and actinomycetes. As compost matures after the thermophilic stage, various
macroorganisms such as earthworms and beetles colonize the decomposing material at
different times and keep displacing each other until stable humus is produced (Cooperband,
2002). The invasion by macroorganisms which was observed in the composts derived from
faeces that were subjected to T3 and T4 storage methods was an indication that these
composts had reached maturity.
69
3.2.4.2
The ammonium concentrations, C:N ratios and changes in the chemical
properties of composted cattle manures
The results of this experiment revealed that there was a slight increase in the N content of
compost derived from faeces of cows whose diet was supplemented with Calliandra and a
reduction in the N contents of composts derived from faeces of cows supplemented with
Centrosema and those fed the control diet. These differences in changes of N contents were
attributed to the levels of polyphenols in the legume supplements. The results of experiment
1 showed that Calliandra contains higher levels of polyphenols than Centrosema. It was also
noted that polyphenols reduce protein digestibility by forming complexes with CP in feeds,
which in turn result in excretion of larger amounts of N in faeces (Delve et al., 2001;
Maasdorp et al., 1999). The results of this experiment indicate that polyphenols continue to
exert their influence on the decomposition and release of N (and other nutrients such as P)
from faeces, hence producing N- (nutrient-) rich compost. However, this influence would
adversely affect the growth of crops if N and other nutrients are not released for crop use at
the time of need. Myers et al. (1994) noted that good manure should synchronise mineral N
release and plant demand such that the peak mineral N release coincides with peak plant
biomass development and hence peak N requirements. Handayanto et al. (1997) observed a
strong relationship between N recovery and the protein-binding capacity of polyphenols,
which suggested that protein-binding by polyphenols was responsible for reduced N recovery
from the slow N release legume tree prunings applied to the soil.
70
The high concentration of NH4-N in the manure compost derived from T2 storage method
was due to anaerobic conditions that were created by the polythene sheet which favoured
anaerobic decomposition (Thomsen, 2000; Martins and Dewes, 1992). It is indicative of an
unstabilised material, which is still undergoing rapid decomposition and not fit to be applied
to soil as organic amendment (Gómez-Brandón et al., 2008). In the earlier stages of
composting, NH4-N is produced by the decomposition of nitrogenous compounds,
particularly proteins. As the compost matures, the NH4-N content drops because of being
oxidized into nitrate by the action of ammonium-oxidizing bacteria. The concentrations of
NH4-N in the manure composts derived from storage methods T1, T3 and T4 were similar to
that (0.4 g kg-1), which is the maximum limit suggested by Zucconi and de Bertoldi (1987)
for the compost that is mature and ready for use as soil amendment.
The results showed that the C:N ratios of composts derived from T3 and T4 storage methods
were similar, but that of the compost derived from T3 was lower than those of composts
derived from T1 and T2. Usually as decomposition of organic materials proceeds, the carbon
content gradually falls, while the concentration of mineralized N increases leading to the
reduction of C:N ratio (Lekasi et al., 2003b). This occurs because each time that organic
compounds are consumed by microorganisms, two-thirds of the carbon is given off as carbon
dioxide. While investigating the effect of storage methods on the properties and degradability
of cattle manure, Atallah et al. (1995) observed that stockpiling or composting of cattle
manure led to significant carbon losses of 17.1 and 26.4% and relative N gains of 25 and
32.7% for stockpiled and composted manure, respectively. As a result, the C:N ratio
decreased with increasing time of storage. The reduction in the C:N ratio continues with
ageing of compost, finally reaching a value which is characteristic of a stable mature
compost.
71
Because of its influence on decomposition and nutrient release (especially N and P), the C:N
ratio is one of the chemical characteristics that can be used to define the manuring quality of
organic soil amendments (Palm et al., 2001). By using the C:N ratio as a measure of manure
quality, the compost derived from T3 storage method would be taken to be superior as a soil
amendment over the composts derived from faeces subjected to T1 and T2 methods. This is
because the compost derived from T3 storage method had a lower C:N ratio than those
derived from the T1 and T2 storage methods. The C:N ratio determines the relative rates of N
immobilization and mineralization from organic materials (Palm et al., 1997). Composts with
lower C:N ratios decompose faster and supply N and other nutrients to the growing crops,
whereas composts with high C:N ratios partially immobilise N, making it unavailable to the
plants for sometime (Delve et al., 2001). Swift et al., (1979) reported that net mineralisation
generally occurs at C:N ratios of less than 23.
The decomposition of OM during the composting process is characterized by changes in
residual rate (i.e., the percentage of OM which remains compared with the original amount).
Significant decline in the OM contents of composts obtained from T3 and T4 storage
methods was attributed to exposure of faeces to the atmospheric air, rainfall and temperature,
and microbes, which accelerated the decomposition process (Somda et al. (1995). Covering
with a polythene sheet in T2 cut off air supply to the faeces, and as a result caused a shift
from aerobic to anaerobic decomposition which is a slow process (Cooperband, 2002). The
reduction in OM contents of cattle manure and other organic wastes during storage and
composting has been reported by Rufino et al. (2007), Bernal et al. (1998) and Atallah et al.
(1995). These researchers attributed the reduction in OM contents to the evolution of CO2,
evaporation of water and particle-size reduction.
72
The results showed an increase in the concentration of N in the compost derived from faeces
that were subjected to the T3 storage method. Studies conducted by Rufino et al. (2007) and
Bernal et al. (1998), revealed that at the onset of decomposition, N losses are greater than
those of carbon leading to a reduction in the concentration of N. But as the decomposition
process proceeds, the concentration of N increases because the rate of OM reduction (loss of
carbon in form of CO2) becomes greater than the loss of N. Therefore, in the T1 and T2
storage methods where the concentrations of N were still declining, the decomposition
process had not yet reached the turning point where the rate of OM reduction becomes
greater than that of N. This means that faeces stored using T1 and T2 methods take longer to
decompose into mature compost. An increase in the concentration of N could have also
occurred in the compost obtained from T4 which experienced aerobic conditions as in T3,
but since the compost in T4 was more exposed to the atmosphere than in T3, higher losses of
N through volatilisation and erosion occurred leading to reduction in the concentration of N.
Similarly, erosion caused by rain was responsible for the decline in the concentration of K in
the compost derived from faeces subjected to T4 storage method.
There was an overall increase in pH levels of the composts from the mean pH 6.6 observed
before subjecting faeces to the storage methods to a mean value of 8.3 at the end of the
storage period. This increase was due to an increase in the concentration of ammonia
resulting from the decomposition of proteins (Lekasi et al., 2003b).
73
3.3.0 EXPERIMENT 3: Growth characteristics and quality of Pennisetum purpureum
following the application of composted cattle manure and mineral fertilisers
3.3.1
Introduction
The excreta of dairy cattle can contribute to the improvement of soil fertility and productivity
if well conserved and recycled. Although animal manure is of major importance in nutrient
recycling on smallholder farms, it may not supply plants with sufficient amounts of nutrients
(Giller et al., 1997). Farmers can only achieve better crop yield responses when they apply
large amounts of animal manure – in the range of 40 t ha−1 (Probert et al., 1995), which
indicates that animal manure alone is ineffective as a source of nutrients for plants, partly due
to large losses of nutrients during storage as revealed in experiment 2. Other researchers,
notably Makokha et al. (2001), Lekasi et al. (2001) and Kihanda (1996) have also reported
that the quantities of manure available on majority of smallholder farms are not enough to
sustain soil fertility. Thus, it is not advisable for farmers to rely entirely on manure as source
of nutrients for plants, especially those with few cows and with small farms. The application
of manure in combination with mineral fertilisers could be a better option, especially for
smallholder farmers with limited cash to purchase mineral fertilisers in sufficient quantities.
The effects of applying a combination of composted cattle manure and mineral fertilisers on
the agronomic performance and nutritive quality of P. purpureum fodder have not yet been
adequately evaluated. It is envisaged that in addition to increasing yields, the application of
composted cattle manure in combination with mineral fertilisers could improve the quality of
P. purpureum fodder. Therefore, the main objective of this experiment was to evaluate the
effect of combined application of composted cattle manure and mineral fertilisers on the
yield and quality of P. purpureum fodder.
74
3.3.2
Materials and methods
3.3.2.1
Production of composted cattle manure and soil preparation
Manure was derived from faeces excreted by dairy cows fed on P. purpureum ad libitum and
supplemented with Calliandra meal was used in this study (Table 9). The soil used in the
experiment was collected from a field at MUARIK, and was a ferrallitic (Harrop, 1970)
sandy-clay loam (Table 9). Prior to the experiment, the soil was sterilised by placing it in a
drum and heating it until a potato embedded in it was cooked ready for eating. It was then
analysed for its physical and chemical characteristics following methods described by
Okalebo (1985). The results are given in Table 9.
Table 9.
Characteristics of composted cattle manure and soil that were used in the
greenhouse experiment (on DM basis)
C
Total N
Total P
Avail. P Avail. K
(g kg-1)
Manure
Soil
3.3.2.2
NH4-N
NO3-N
pH
(mg kg-1)
453.6
18.6
7.3
0.94
----
0.36
----
7.8
25.3
2.0
1.7
0.03
0.27
0.06
0.06
6.2
Experimental design and measurements
The greenhouse experiment comprised twelve treatments arranged in a split plot design with
three main plots, four sub-plots and replicated four times (Table 10). The experimental unit
was a 25 cm diameter plastic pot filled up to the height of 20 cm with 10 kg of sandy-clay
loam soil (dry weight basis). The composted cattle manure and mineral fertilizers [urea (46%
N) and SSP (18% P)] which were added to each pot were thoroughly mixed with 8 kg soil,
placed in the pot and covered with additional 2 kg of soil to provide a manure-free layer that
75
would minimize NH3 volatilization. The main plots comprised three soil amendment
treatments namely; sole composted cattle manure application, sole mineral fertiliser
application and composted cattle manure + mineral fertiliser application. Each of the
amendments was applied at four rates that supplied N and P as described in Table 10. These
nutrient elements (N and P) were selected because they are needed by P. purpureum in large
amounts and yet are deficient in most tropical soils. Boonman (1993) reported that P.
purpureum requires 100, 22 and 22 kg ha-1 of N, P and K respectively, in order to grow well.
The rates of composted cattle manure application in treatments which received manure alone
were zero, 2.7, 5.4 and 10.8 ton ha-1 for the control, ML, MM and MH, respectively. These
rates of manure application supplied P at rates of zero, 19.6, 39.1 and 78.2 kg P ha-1,
respectively (Table 10).
For the case of treatments which received mineral fertilisers only, they were applied at rates
that supplied same amounts of N and P as composted cattle manure, that is, zero (control), 50
(FL), 100 (FM) and 200 (FH) kg N ha-1) and zero (control), 19.6, 39.1 and 78.2 kg P ha-1.
The rates of urea application that supplied the same amounts of N as cattle manure were 110,
220 and 440 kg ha-1 for FL, FM and FH, respectively. Similarly, the rates of SSP application
that supplied the same amounts of P as the manure were 110, 220 and 440 kg ha-1 for FL, FM
and FH, respectively. The treatments where combinations of composted cattle manure and
mineral fertilisers were applied, the two sources of N and P were combined in a way that
each contributed half the amount of N and P that would lead to the application rates of zero
(control), 50 (MFL), 100 (MFM) and 200 (MFH) kg N ha-1 and zero (control), 19.6, 39.1 and
78.2 kg P ha-1 (Table 10).
76
Table 10. Description of the treatments
Treatment
N
P
Nutrient sources
(kg ha-1)
Control
0
0
Zero manure and fertilizers added
ML
50
19.6
Manure only
MM
100
39.2
Manure only
MH
200
78.4
Manure only
FL
50
19.6
Urea and Single superphosphate
FM
100
39.2
Urea and Single superphosphate
FH
200
78.4
Urea and Single superphosphate
MFL
25
25
9.8
9.8
Manure
Urea and Single superphosphate
MFM
50
50
19.6
19.6
Manure
Urea and Single superphosphate
MFH
100
100
39.2
39.2
Manure
Urea and Single superphosphate
ML, MM and MH = Low, Medium and High rates of manure-only application, respectively;
FL, FM and FH = Low, Medium and High rates of fertiliser-only application, respectively;
MFL, MFM and MFH = Low, Medium and High rates of composted cattle manure + mineral
fertiliser combinations, respectively.
One P. purpureum cutting with two nodes was planted by laying it horizontally at a depth of
3 cm below the soil surface in each plastic pot. The pots were irrigated every the other day
with two litres of tap water to ensure that they are maintained at the same moisture content of
80% field capacity. All the P. purpureum cuttings sprouted well. Counting of leaves and
measuring leaf sizes to determine the leaf area index (LAI) commenced at the end of third
week from planting date, and was repeated fortnightly up to week 11. The area of each leaf
77
was calculated using the formula 0.71 (length x width), where 0.71 is a constant for grasses.
The LAI was then calculated by dividing the total leaf area at a particular time of
measurement, with the area of soil surface in the plastic pot.
Harvesting of the above ground biomass in each pot was done at the end of week 11. Fodder
was chopped into pieces of about 5 cm length, placed in a polythene bag and weighed
immediately. After weighing, chopped fodder was dried in the oven at 60 0C for 72 hours and
then weighed to determine fodder DM yield per pot. Fodder from each pot was then
separated into leaf and stem, and each portion weighed. After harvesting fodder, the pots
were watered and left undisturbed so that P. purpureum sprouts again. The above procedure
was repeated for four consecutive rounds, each lasting for eleven weeks.
3.3.2.3
Chemical analysis of samples
The leaf and stem portions from each pot were recombined and ground to pass through a
1mm sieve. Ground samples were then analysed to determine their OM contents by loss on
ignition at 5500C, and total N, P, K and Ca using the wet acid oxidation (Okalebo, 1985). The
fibre (NDF, ADF and ADL) contents were determined using the Van Soest and Robertson
(1985) method and the in vitro organic matter digestibility (IVOMD) by Tilley and Terry
(1963) technique. Calcium and K were assayed using the flame photometer (Model PFP7,
Jenway Co. Ltd), while P was assayed using the colorimeter (Model CO 700).
78
3.3.2.4
Statistical analysis of data
Statistical analyses of data were carried out using factorial ANOVA of the Statistical
Analyses Systems (SAS, 2004) and following the model outlined below.
Xij
where,
=
 + i + j + ij + ij;
i and j = 1 ......a
Xij = the jth observation on the response variable under the ith treatment
 = Mean
 = Manure treatment effect
 = Fertiliser treatment effect
 = Manure + Fertiliser treatment effect
 = Random error effect
Mean comparisons were made using the least significant difference (LSD) and differences
were considered significant at the 5% level.
79
3.3.3
Results
3.3.3.1
Growth Characteristics
3.3.3.1.1
Leaf area index
The LAIs for all treatments increased gradually as the period of growth advanced up to the
eleventh week (Fig. 2). The P. purpureum plants were able to regenerate after every round of
harvesting. At the age of three weeks, the LAIs of all the treatments were similar, except
those of FH, ML and MFM which were higher than that of the control. At five and seven
weeks of growth, no significant differences were observed between the LAIs of all
treatments, apart from those of MM and ML which were greater than that of the control. At
the ninth week of growth, the LAIs of MM and ML were persistently greater than that of the
control. However, no differences were observed among the composted cattle manure-only, as
well as those of fertiliser-only treatments. For the case of composted cattle manure + fertiliser
treatments, the LAI of MFH was similar to that of MFM but higher than that of MFL.
At eleven weeks of growth, the LAIs of ML, MM, MH, MFH and FL were superior to that of
the control. No differences were observed among the composted cattle manure-only
treatments. For the case of fertiliser-only treatments, the LAI of FL was similar to that of FH
but higher than that of FM. For the case of composted cattle manure + fertiliser treatments,
the LAI of MFH did not differ from that of MFM but was higher than that of MFL.
Comparisons between the composted cattle manure-only and fertiliser-only treatments
revealed that the LAIs of composted cattle manure-only treatments were higher than those of
fertiliser-only treatments, except that of FL. The comparison between composted cattle
manure-only and the composted cattle manure + fertiliser treatments showed that the LAI of
MM did not differ from those of MFM and MFH but was superior to that of MFL.
80
8
7
Ctrl
ML
6
Leaf area index
MM
5
MH
FL
4
FM
FH
3
MFL
2
1
MFM
FMH
(LSD0.05 )
0
Week 3
Week 5
Week 7
Week 9
Week 11
Time in weeks
ML, MM and MH = Low, Medium and High rates of manure-only application, respectively;
FL, FM and FH = Low, Medium and High rates of fertiliser-only application, respectively;
MFL, MFM and MFH = Low, Medium and High rates of composted cattle manure + mineral fertiliser combinations, respectively
Fig. 2: Increase in the leaf area index of Pennisetum purpureum plants as growth period advances
81
At the first harvest, the LAIs of P. purpureum plants differed significantly between
treatments (Table 11). The LAIs for all treatments were higher than that for the control with
the exception of FM and MFM whose LAIs were similar to that of the control. Among the
composted cattle manure-only treatments, the LAI of ML was higher than those of MM and
MH. For the case of the fertiliser-only treatments, the LAI of FM was lower than those of FL
and FH. Among the composted cattle manure + fertiliser treatments, MFH had higher LAI
than MFL and MFM.
Table 11.
Mean leaf area index of Pennisetum purpureum fodder at harvesting stage
Treatment
1st harvest
2nd harvest
3rd harvest
4th harvest
ML
3.89ab
4.56bc
3.71b
2.14c
3.58a
MM
3.08cd
4.55c
4.55a
2.59a
3.69a
MH
3.22cd
4.38cd
3.50cd
2.14c
3.31bc
FL
3.81ab
4.48cd
3.12e
2.17bc
3.39b
FM
2.15f
4.28d
3.38cd
1.92cd
2.93d
FH
3.43bc
4.77ab
2.83f
1.79d
3.21c
MFL
3.27cd
3.71e
2.71f
2.44ab
3.03d
MFM
2.91de
4.40cd
3.31d
2.49a
3.28bc
MFH
3.95a
4.93a
3.43cd
1.90cd
3.56a
Control
2.56ef
2.91f
3.55bc
2.54a
2.89d
Mean
3.12
4.07
3.43
2.27
3.22
LSD(0.05)
0.49
0.22
0.19
0.28
0.15
Mean
abcd
Means within the same column followed by different superscripts differ (P<0.05); LSD = Least
Significant Difference; *** = P<0.001.
ML, MM and MH = Low, Medium and High rates of manure-only application, respectively;
FL, FM and FH = Low, Medium and High rates of fertiliser-only application, respectively;
MFL, MFM and MFH = Low, Medium and High rates of composted cattle manure + mineral
fertiliser combinations, respectively.
82
Comparison between composted cattle manure-only and fertiliser-only treatments indicated
that the LAI of FL was greater than those of MM and MH, while that of FM was lower than
those of the composted cattle manure-only (ML, MM and MH) treatments. Comparison
between composted cattle manure-only and the composted cattle manure + fertiliser
treatments indicated that the LAIs of ML and MFH were similar. However, the LAI of ML
was greater than those of MFL and MFM, while that of MFH was greater than those of MM
and MH. Comparison between the fertiliser-only and composted cattle manure + fertiliser
treatments indicated that the LAI of FL was similar to that of MFH, but the LAI of FL was
greater than those of MFL and MFM, while that of FM was lower than those of the
composted cattle manure + fertiliser treatment combinations.
At the second round of harvesting, the LAIs for all treatments were greater than that of the
control (Table 11). The LAIs for the composted cattle manure-only treatments did not differ
from each other. For the case of fertiliser-only treatments, the LAI of FH was higher than
those of FL and FM. The LAIs for the composted cattle manure + fertiliser treatments
increased linearly with rates of composted cattle manure + fertiliser application, and were all
significantly different from each other. The LAIs for the low (ML) and medium (MM) rates
of composted cattle manure application were higher than that of the medium rate (FM) of
fertiliser-only treatment. The LAIs for the composted cattle manure-only treatments were
lower than that of MFH, but were greater than that of MFL. Comparisons revealed that LAIs
for all the fertiliser-only treatments were higher than that of MFL. However, LAIs for the
low and medium rates of fertiliser-only treatments were lower than that for the high rate
(MFH) of composted cattle manure + fertiliser treatment.
83
There was greater variation in the LAIs of all treatments at the third round of harvesting
(Table 11). Apart from the LAI of MM which was higher, those of the other composted cattle
manure-only treatments were similar to that of the control. With the exception of FM and
MFH, the LAIs for the fertiliser-only as well as the composted cattle manure + fertiliser
treatment combinations were lower than that of the control. Among the composted cattle
manure-only and the fertiliser-only treatments, the LAIs varied in the order MH < ML < MM
and FH <FL < FM, respectively. For the case of the composted cattle manure + fertiliser
treatments, the LAIs of MFM and MFH were similar, but were greater than that of MFL. The
LAIs for FL and FH rates of fertiliser-only treatments were lower than those for the
composted cattle manure-only treatments, while the LAI for the FM rate of fertiliser-only
treatment was lower than those for ML and MM rates of composted cattle manure-only
treatments. A comparison between the composted cattle manure-only and the composted
cattle manure + fertiliser treatments indicated that the LAIs for ML and MM were greater
than those for the composted cattle manure + fertiliser treatments. The fertiliser-only and
composted cattle manure + fertiliser treatment comparisons indicated that the LAIs for FL
and FM were greater than that for treatment MFL, while those for treatments FL and FH
were lower than those for treatments MFM and MFH.
At the fourth round of harvesting, the LAIs for all treatments were lower than that of the
control apart from those of MM, MFL and MFM which were similar (Table 11). Among the
composted cattle manure-only treatments, the LAI of MM was greater than those of ML and
MH. For the case of the fertiliser-only treatments, the LAI for FL was similar to that of FM
but was greater than that of FH. Among the composted cattle manure + fertiliser treatments,
the LAIs of MFL and MFM were higher than that of MFH. Observations also indicated that
84
the LAIs of all the fertiliser-only treatments were lower than that of MM, while that of FH
was lower than those of ML and MH. A comparison between the composted cattle manureonly and the composted cattle manure + fertiliser treatments indicated that the LAIs of MFL
and MFM were greater than those of ML and MH, and that of MFH was lower than that of
MM. The fertiliser-only and the composted cattle manure + fertiliser treatment comparison
revealed that the LAI for MFL was greater than those of FM and FH, while that of MFM was
greater than those of the fertiliser-only treatments.
Pooled statistical analysis of data across the four rounds of harvesting showed that
harvesting, treatments as well as the interaction between harvesting and treatments
significantly influenced the LAIs of P. purpureum plants. With the exception of FM and
MFL, the mean LAIs for all treatments were higher than that of the control. Among the
composted cattle manure-only treatments, the LAIs of ML and MM were greater than that of
MH. For the case of fertiliser-only treatments, the LAIs for all treatments differed
significantly from each other, with that of FL being the greatest followed by that of FH and
FM, respectively. Leaf area indices for the composted cattle manure + fertiliser treatments
also differed significantly from each other, with that of MFH being higher, followed by that
of MFM and MFL, respectively. The LAIs for the low (ML) and medium (MM) cattle
manure-only treatments were greater than those of the fertiliser-only treatments. With the
exception of MFH whose LAI was similar to those of ML and MM, the LAIs for the
composted cattle manure-only treatments were greater than those of the composted cattle
manure + fertiliser treatments. Although the LAIs of FL and FH were greater than that of
MFL, the LAIs for all the fertiliser-only treatments were lower than that of MFH.
85
Statistical analysis of pooled data also revealed that the mean LAI for all treatments at each
round of harvesting significantly increased from 3.12 at first harvest to 4.07 at the second
harvest, and thereafter dropped to 3.43 and 2.27 at the third and fourth rounds of harvest,
respectively (Table 11). When averaged across main treatments, the LAIs across the four
rounds of harvesting were in the order 2.89 < 3.18 < 3.29 < 3.53 for the control, fertiliseronly, composted cattle manure + fertiliser and the composted cattle manure-only,
respectively and highly differed (P<0.0001) from each other (LSD0.05 = 0.09).
3.3.3.1.2
Fodder dry matter yields and in vitro organic matter digestibility
Composted cattle manure significantly increased fodder yields (Table 12). Sole application of
fertilisers at different rates did not cause significant increase in fodder yields. The medium
(MFM) and higher (MFH) rates of composted cattle manure + fertiliser treatment
combinations produced fodder yields which were similar to those of the composted cattle
manure-only treatments, and were also greater than that of the control. Comparisons revealed
that the lowest rate of composted cattle manure-only (ML) treatment yielded more fodder
than the medium rate of fertiliser-only (FM) treatment. Also, the lowest and medium rates of
composted cattle manure-only treatments yielded more fodder than the lowest rate of
composted cattle manure + fertiliser (MFL) treatment
Statistical analysis of pooled data indicated that fodder DM yields across the four rounds of
harvesting increased in the order 5.61 < 6.25 < 6.58 < 6.96 ton ha-1 for the control, fertiliseronly, composted cattle manure + fertiliser combinations and composted cattle manure-only
treatments, respectively. Thus the overall fodder DM yield for the composted cattle manureonly treatments did not differ from that of the composted cattle manure + fertiliser treatment
86
combinations, but was superior to those for the fertiliser-only treatments and the control
(LSD0.05 = 0.69). The fodder DM yield for the composted cattle manure + fertiliser
combinations was similar to that of the fertiliser-only treatments, but was greater than that of
the control.
Table 12. Dry matter yields, morphological fractions and IVOMD of Pennisetum
purpureum fodder following the application of composted cattle manure alone, mineral
fertilisers alone and composted cattle manure + mineral fertiliser combinations
Fodder dry matter yields, morphological fractions and IVOMD
Treatments
Total fodder yield
(ton ha-1)
Leaf yield
(ton ha-1)
Stem yield
(ton ha-1)
ML
7.15a
5.45ab
1.71abc
560.9b
MM
6.99ab
5.58a
1.43abcd
628.3a
MH
6.74abc
5.03abcd
1.72abc
615.2a
FL
6.29abcd
4.90abcd
1.40bcd
623.9a
FM
5.98bcd
4.67bcd
1.32cd
597.1ab
FH
6.48abcd
4.60cd
1.90ab
598.4ab
MFL
5.91cd
4.84abcd
1.17d
612.8a
MFM
6.80abc
4.90abcd
1.91a
589.5ab
MFH
7.01ab
5.30abc
1.72abc
606.0a
Control
5.61d
4.47d
1.18d
513.6c
LSD(0.05)
1.06
0.81
0.50
39.2
abcd
IVOMD
(kg ton-1)
Means within the same column followed by different superscripts differ (P<0.05).
ML, MM and MH = Low, Medium and High rates of manure-only application, respectively;
FL, FM and FH = Low, Medium and High rates of fertiliser-only application, respectively;
MFL, MFM and MFH = Low, Medium and High rates of composted cattle manure + mineral
fertiliser combinations, respectively.
87
Yields of P. purpureum leaves and stems varied (P<0.05) between treatments (Table 12).
Leaf yields of the low (ML) and medium (MM) rates of composted cattle manure application
were significantly higher than that of the control. However, leaf yields of the fertiliser-only
treatments were similar across all the rates of application as well as the control. The leaf
yields of the composted cattle manure + fertiliser treatment combinations did not differ from
that of the control, except MFH whose leaf yield was superior.
With the exception of MM, FL, FM and MFL the proportions of stem in fodder from all
treatments were higher than that of the control (Table 12). Among the fertiliser-only
treatments, fodder from FH had higher stem than that from FM; while among the composted
cattle manure + fertiliser treatment combinations, fodder from MFL had lower stem than that
from MFM and MFH.
The application of composted cattle manure, mineral fertilisers and composted cattle manure
+ fertiliser combinations led to the production of P. purpureum fodder with better IVOMD
compared with the control (Table 12). Among the composted cattle manure-only treatments,
the IVOMD levels of MM and MH were similar, but were higher than that of ML which
indicated an improvement in the digestibility of fodder as the quantity of composted cattle
manure applied increased. No differences were observed among IVOMD levels of fodder
from the fertiliser-only as well as the composted cattle manure + fertiliser treatments.
Chemical analysis of fodder did not show remarkable differences in the concentrations of
OM, N, P, K, Ca, NDF, ADF and ADL of fodder obtained from composted cattle manureonly, fertiliser-only and composted cattle manure + fertiliser treatments (Table 13).
88
Table 13. Effects of composted cattle manure and mineral fertilisers on chemical composition of P. purpureum fodder
Chemical components and in vitro organic matter digestibility of fodder
Treatments
OM
Ash
N
P
K
Ca
NDF
ADF
ADL
g kg-1 DM
ML
874.6a
125.4c
15.8b
2.60ab
25.2bc
2.89ab
583.8
375.0ab
70.0bc
MM
868.3ab
131.7bc
16.5ab
2.89a
25.8bc
2.64b
567.6
365.0b
91.3ab
MH
864.1b
136.0b
16.5ab
2.48bc
27.9abc
2.68ab
590.0
402.5ab
73.8bc
FL
861.8b
138.2b
17.5a
2.27c
26.6bc
3.00ab
586.3
491.3a
103.8a
FM
866.4ab
133.6bc
16.9ab
2.27c
28.7ab
3.02a
587.5
377.5ab
82.5abc
FH
867.7ab
132.3bc
16.8ab
2.33bc
24.6c
2.91ab
598.8
416.3ab
86.3ab
MFL
849.2c
150.8a
17.2a
2.22c
27.9abc
2.69ab
565.0
377.5ab
73.8bc
MFM
866.4ab
133.6bc
16.3ab
2.28c
24.8c
2.67ab
581.3
369.4b
72.5bc
MFH
864.9ab
135.1bc
17.3a
2.30bc
24.4c
3.01ab
557.5
366.3b
58.8c
Control
859.5b
140.5b
16.8ab
2.54bc
30.4a
2.84ab
560.0
403.8ab
76.3bc
Treatment means
864.3
135.7
16.8
2.4
26.6
2.8
577.8
394.5
78.9
LSD(0.05)
10.3
10.3
1.3
0.32
3.8
0.36
42.2
121.4
25.3
abc
Means within a column followed by different superscripts differ (P<0.05).
89
3.3.4
3.3.4.1
Discussion
Growth Characteristics
3.3.4.1.1 Leaf area index
Results showed that the application of composted cattle manure, mineral fertilisers and
composted cattle manure + fertiliser combinations improved the LAI of P. purpureum plants
when compared to the control. Comparisons also revealed that LAIs of composted cattle
manure-only treatments (ML and MM) were higher than those of the fertiliser-only
treatments. This was attributed to the fact that in addition to N and P, composted cattle
manure supplied other nutrients, such as calcium and potassium, all of which had an
influence on the growth of P. purpureum plants (Chadwick et al., 2000). In addition to
supplying nutrients, manures affect plant growth indirectly by improving the physical,
chemical and biological properties of soil, such as water retention, aeration, pH, cation
exchange capacity and microbial activity and diversity (Cooperband, 2002; Kihanda and
Gichuru, 1999; Harris et al., 1997). Reddy et al. (2000) observed that because of its buffer
action on pH, manure increases the levels of P in the soil available to crops than when
inorganic fertiliser P is applied at the same rate. The LAI for the low rate of composted cattle
manure + fertiliser combination (MFL) was similar to that of the control indicating that the
amount of manure added was low to have an effect on the properties of soil.
Leaves of forage plants are usually better in nutritive quality, particularly in terms of CP
content and digestibility, than stems from the same plant. Therefore, the higher the leaf
component in fodder, the better the nutritive quality. Collins and Fritz (2003) noted that
forage quality is a function of voluntary intake. When given the opportunity, ruminants
usually select leafy forages over those with higher proportions of stem material. It is also
90
important to note that while the nutritive quality of leaves changes little as shoots mature, the
fibre content in maturing stems increases rapidly and as a result their digestibility declines
(Collins and Fritz, 2003).
Results also indicated that the LAI increased from 3.12 at first harvest to 4.07 at second
harvest, and thereafter dropped to 3.43 and 2.27 at the third and fourth rounds of harvesting,
respectively. The increase in LAI at the second harvest was attributed to the increased supply
of readily available N, P and other nutrients from the composted cattle manure and mineral
fertilisers. The decrease in LAI thereafter was attributed to the gradual decline in the release
of organically bound nutrients, especially nitrogen in the manure (Sørensen and Amato,
2002; Eghball, 2000). The overall mean LAI for the composted cattle manure-only
treatments was superior to that of the composted cattle manure + fertiliser treatments.
Manure application rates in the composted cattle manure-only treatments were twice that in
the manure + fertiliser treatments. Therefore, the superiority of the LAI for composted cattle
manure-only treatments confirms the report by Probert (1995) that better crop responses are
achieved when cattle manure is applied in large amounts. Manures mineralize and release
nutrients slowly, and therefore, their nutrient supplying capacity lasts a little longer than that
of mineral fertilisers (Paul et al., 1998). This was the reason why LAIs of composted cattle
manure-only treatments were greater than those of the fertiliser-only treatments
3.3.4.1.2 Fodder dry matter yields and in vitro organic matter digestibility
Results indicated that fodder DM yields for the composted cattle manure-only (ML, MM and
MH) and the medium (MFM) and high (MFH) rates of composted cattle manure + fertiliser
treatments were greater than that of the control. This was attributed to the ability of
composted cattle manure to supply a variety of nutrients other than N and P, and by
91
improving the physical, chemical and biological properties of soil. The fodder DM yield
advantage in response to manure and manure + fertiliser application was also attributed to the
slow release of organic nutrients in the manure, which could have benefited the plants over
the growing period. Whereas nutrients in fertilisers are in readily soluble form, and therefore,
become available to crops immediately following application, nutrients in manure must
mineralize, and thus stay longer in the soil for the benefit of the growing plants over the
growing seasons (Eghball and Power, 1999; Williams et al., 1995; Bationo and Mokwunye,
1991). Paul et al. (1998) observed that although the soil inorganic N concentrations
decreased with successive corn harvests, the decrease was not as great with the manure
treatments compared to the fertiliser treatments. This indicated that either soil N losses were
lower with the manure treatments, or that there was continuous mineralisation of manure
organic N. A study conducted by Kabirizi (2006) in Masaka District, Uganda revealed that P.
purpureum fodder DM yields were quite low (4.17 ton ha-1 year-1) in urban areas as compared
to fodder yields in the peri-urban and rural areas (4.95 and 5.72 ton ha-1 year-1, respectively).
Therefore, utilization of cattle manure either alone or in combination with mineral fertilizers
as reported in this study, especially in the urban areas where cultivation is intensive would
alleviate the problem of low fodder yields.
The results of experiment 1 indicated that dairy cows whose diets were supplemented with
leguminous forages consumed on average 9.6 kg DM of P. purpureum daily (Table 3). In
experiment 3, treatments (ML, MM, MH, MFM and MFH) whose P. purpureum fodder
yields were superior produced on average 7.0 ton ha-1 of fodder (Table 12). This amount of
fodder, when supplemented with leguminous forages and dairy meal at rates used in this
study would be able to support two dairy cows for a year.
92
It has been observed that organic and inorganic materials have a complementary role and
their simultaneous use gives better crop yields than when they are applied separately (Kimani
et al., 2004; Ahmed and Sanders, 1998; Bationo et al., 1998). Studies of Kimani et al. (2004)
indicated that combining manures with mineral fertilisers was more effective in the
production of maize, compared to singular application of manure (5 ton ha-1) and mineral
fertiliser (Di-ammonium phosphate) alone applied at rates below 100 kg N ha-1. However,
the results of this study have not shown such yield advantage.
Fodder obtained from ML, MM and MFH contained greater proportions of leaf than fodder
from the control. This suggests that there was greater vegetative growth in these treatments
as compared to the control. In addition to having higher CP than stem, leaves of plants
usually contain less fibre and thus are easily digested than stems. Because of these two
reasons, higher leaf content is an indication of improvement in the quality of fodder.
Therefore, fodder from treatments ML, MM and MFH was regarded to be of better quality
than that from the control.
The IVOMD levels of fodder from all treatments were similar but greater than that of the
control. This implies that sole application of cattle manure or supplementing it with mineral
fertilisers would lead to production of fodder with the digestibility similar to that of fodder
produced using mineral fertilisers. Highly digestible forages increase animal production
largely by increasing their energy intake. Therefore, by conserving and utilizing cattle
manure produced on farm, dairy farmers would benefit by minimizing the expenditure on
quantities of mineral fertilisers to be purchased.
93
CHAPTER FOUR
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS
4.1
Summary and conclusions
The general objective of this study was to investigate whether legume supplementary feeding
to dairy cattle offered P. purpureum basal diet improves feed intake and manuring quality of
the ensuing cattle faeces; and whether if properly managed and applied in combination with
mineral fertilisers in the field, cattle manure enhances yield and quality of P. purpureum
fodder. Specific objectives of the study were (i) to determine the effect of legume
supplementary feeding to dairy cows offered P. purpureum basal diet on feed intake, faecal
output and faecal nutrient concentration, (ii) to develop regression models for predicting
faecal output and the amounts of N and P excreted in faeces by dairy cows offered P.
purpureum basal diet and supplemented with legume foliage meal, (iii) to identify the most
effective method of storing cattle faeces which will lead to production of compost with better
manuring quality, and (iv) to evaluate the effect of combined application of composted cattle
manure and mineral fertilisers on the yield and quality of P. purpureum fodder.
In experiment 1, supplementing P. purpureum diet offered to lactating dairy cows with
legume foliage meal significantly increased feed (DM and OM) intake as well as nutrient (N,
P, K and Ca) intake, ADMD, ME intake and milk yield. Faecal-DM and OM excretions were
significantly increased by Calliandra and Centrosema, and not by Desmodium. Faecal–N, P
and K were higher in Calliandra supplemented diets, while Ca was higher in Calliandra and
Centrosema supplemented diets. Therefore, supplementing P. purpureum diet offered to
lactating dairy cows with legume foliage meal particularly Calliandra enhances feed intake,
and consequently the amounts of faeces and faecal nutrients, especially N and P available for
94
recycling within the crop-livestock production systems. Since legume forages are grown onfarm and not purchased as is the case with commercial concentrates, there is no reason why
farmers should not adopt or continue using them as supplements to the P. purpureum diet.
After all, supplementing P. purpureum basal diet offered to dairy cows with legume forages
enhances milk production. Therefore, increased output and manuring quality of faeces
excreted would be an added benefit to the farmers especially if the faeces are conserved and
recycled into the system as a soil amendment.
The results of experiment 1 also revealed that the amounts of faeces as well as those of N and
P excreted in faeces by lactating dairy cows offered P. purpureum and legume foliage meal
are closely related to the intake of feed, N and P and can thus be predicted by multivariate
prediction equations, such as developed herein. Accurate measurement of DM intake
together with good estimates of dietary–N and P contents, and diet ADMD provide the
information needed to accurately predict faecal output, and N and P excretions. The ability of
farmers to predict faecal output and the amounts of N and P excreted in faeces by lactating
dairy cows is one of the steps towards developing a manure management plan for
maximizing the utilisation of livestock manure as a soil amendment resource.
Experiment 2 determined the impact of method of storing faeces excreted by dairy cows
offered P. purpureum–legume foliage meal diets on the manuring quality of the resultant
manure compost. The compost derived from faeces which were stored in open pits (T3) was
at an advanced stage of decomposition and exhibited features of maturity, namely fine
texture, homogeneous colour, inoffensive smell, presence of macroorganisms and a lower
concentration of NH4-N. This suggests that storing cattle faeces in open pits produces mature
compost in a shorter time than when wrapped in polythene sheet (T2 method) or placed in
95
pits and covered with soil (T1 method). Also the manuring quality of compost derived from
faeces stored in open pits was better because its N losses as well as its C:N ratio were low
compared to those of composts derived from the other storage methods. Stockpiling cattle
faeces adjacent to the stall (T4 method), which is common among the smallholder dairy
farmers in the urban/peri-urban areas, leads to production of poor quality manure compost
because of higher N and K losses through volatilization and erosion. Therefore, basing on the
results of the current study it is concluded that storing cattle faeces in open pits following
removal from the stall would be the most appropriate and low-cost management intervention.
In experiment 3, the effect of combining composted cattle manure with mineral fertilisers on
the yields and quality of P. purpureum fodder was evaluated in the greenhouse. Sole
application of composted cattle manure at low (ML), medium (MM) and high (MH) rates
(i.e., 2.7, 5.4 and 10.8 ton, respectively), or in combination with mineral fertilisers at medium
(MFM = 2.7 ton + 110 kg SSP + 110 kg urea) and high (MFH = 5.4 ton + 220 kg SSP + 220
kg urea) rates improved the growth of P. purpureum fodder in terms of LAIs and DM yields.
Also, fodder obtained from ML, MM and MFH contained greater proportions of leaf and had
higher IVOMD than fodder from the control, and therefore, was regarded to be of better
quality. Basing on these results, it was concluded that sole application of composted cattle
manure at rates ML, MM and MH or in combination with SSP and urea at rates MFM and
MFH has the potential of improving the yields and quality of P. purpureum fodder. However,
there was no advantage in applying composted cattle manure in combination with mineral
fertilisers over sole manure application, since both treatments produced similar quantities of
fodder with similar digestibilities. This suggests that composted cattle manure should only be
supplemented with mineral fertilisers in case its’ supply is inadequate.
96
4.2
Contribution of improved cattle diet and management of ensuing manure to the
productivity and sustenance of dairy production in urban and peri-urban areas
Smallholder dairy production in the urban/peri-urban areas of Uganda depends mainly on P.
purpureum fodder, and improve its nutritive value by supplementing it with leguminous
forages to maximize intake and milk output from Friesian x Zebu crossbred dairy cows.
However, the current trends in agricultural intensification are leading to a progressive decline
in the nutrient stocks of agricultural soils. Consequently, the quantity and quality of P.
purpureum fodder is declining resulting in reduced animal production in terms of milk yield.
The results of this study showed that in addition to increasing milk yield, legume
supplementation increases the output and mineral content (fertiliser value) of faeces excreted
(Fig. 3). Thus, the growing dairy cattle population in the urban/peri-urban areas coupled with
improvement in feeding is generating more manure, which if well managed can become an
input in P. purpureum fodder production. Manure has been, and continues to be, an important
source of nutrients and OM in the smallholder crop-livestock farming systems where the use
of mineral fertilisers is hampered by limited accessibility and high cost. The current practice
of livestock manure disposal is that farmers scrape it from the stalls and pile it on bare
ground adjacent to the stalls and leave it exposed to sunshine and rain leading to loss of
nutrients and OM through leaching, volatilization and erosion. This leads to the production of
poor quality manure compost (Rufino et al., 2007). This study identified that storing cattle
faeces in open pits following removal from the stall would be the most appropriate and lowcost management intervention.
97
Legume
supplement
Pennisetum
purpureum
basal diet
Better quality
diet offered
to dairy cows
Improved Pennisetum
purpureum fodder
yields and quality
Supplementing
cattle manure
with mineral
fertilisers
Improved
feed intake
Improved
soil fertility
Application of
better quality
cattle manure
Better faecal
handling and
storage
Higher faecal
output with better
manuring quality
Minimal loss
of manure
nutrients
Fig. 3. Synthesis model of improvement in nutrient quality of cattle manure for
utilisation in the urban and peri-urban areas
98
Higher
milk
yield
With improved manure nutrient use efficiency, production of more P. purpureum fodder
would be achieved. Insufficiency of cattle manure to fully sustain the productivity on some
farms can be corrected by strategically combining the available manure with mineral
fertilizers. This was demonstrated by the results of this study when sole application of
properly managed cattle manure at low, medium and high rates or in combination with
fertilisers at medium and high rates improved the yields and quality of P. purpureum fodder.
The mean fodder DM yield from these treatments was 7.0 ton ha-1, which was greater than
4.2 ton ha-1 reported by Kabirizi (2006). When this amount is supplemented with leguminous
forages and dairy meal at rates used in this study, it would be able to support two dairy cows
for a year.
Therefore, improved cattle diet and management of ensuing manure increases the productivity
of dairy production. However, this is likely to offer short-term gains to smallholder production
systems where external inputs (feeds and fertilizers) are rarely used. Without use of external
inputs, nutrient removal and export in form of products, particularly milk, may lead to
nutrient depletion. Therefore, it is unlikely for continued use of cattle manure alone generated
on-farm to maintain a stable and self-renewable nutrient reservoir by replacing all the
nutrients removed from the soil and incorporated in animal products. Thus, there is need for
farmers to strategically combine cattle manure with mineral fertilisers if they are to achieve
long-term positive farm nutrient balances.
99
4.3
Recommendations
Based on the results, the following recommendations were made.
1.
Majority of smallholder dairy farmers in urban/peri-urban areas of Uganda use P.
purpureum fodder as basal diet for dairy cattle and supplement it with leguminous
forages, mostly Calliandra. These farmers need to be encouraged and supported to
grow more leguminous forages since this would further increase milk yield as well as
faecal output and faecal nutrients available for recycling within the crop-livestock
production systems.
2.
Equations for predicting quantities of faeces and the concentrations of N and P in the
faeces excreted by lactating crossbred dairy cows offered P. purpureum and legume
foliage were developed. However, further research is required to validate these
equations if they have adequate precision and accuracy for use under the conditions
prevailing on smallholder farms.
3.
There is need to encourage farmers to adopt the practice of storing cattle faeces in open
pits instead of stockpiling them adjacent to the stall, which results in losses of OM and
manure nutrients through leaching, volatilization and erosion. Farmers should stop
looking at livestock excreta as a waste, but as an input with an added benefit when well
conserved and recycled back into the production system.
4.
The results of this study showed that sole application of properly managed cattle
manure at low, medium and high rates or in combination with fertilisers at medium and
high rates as used in the study has potential of improving yields and quality of P.
purpureum fodder. However, further research is required to elucidate the effects of
applying cattle manure alone or in combination with mineral fertilisers under the
farmer’s field conditions. It is unlikely for cattle manure alone to replace all the
100
nutrients removed from the soil and incorporated in animal products, particularly milk;
and thus the need for farmers to supplement cattle manure with mineral fertilisers if
they are to maintain positive farm nutrient balances.
5.
Applying a combination of composted cattle manure and mineral fertilisers would
reduce the farmer’s expenditure on the purchase of mineral fertilisers, since fewer
quantities of mineral fertilisers would be purchased. However, further research focusing
on the economic benefit of livestock manure management and application in
combination with mineral fertilisers in P. purpureum fodder production needs to be
conducted. In addition, research aimed at designing efficient livestock manure
management approaches that can reduce the costs involved in recycling livestock
manure is required.
101
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122
APPENDICES
Appendix Fig. 1: Rainfall distribution and mean maximum temperature variation at
Makerere University Agricultural Research Institute Kabanyolo from July 2004 to
35
100
30
25
80
20
60
15
40
10
5
0
0
J
-3 ul
01 1 J
-1 ul
5
16 Au
-3 g
1
01 Au
-1 g
5
16 Se
-3 p
0
01 Se
-1 p
5
16 O
-3 ct
01 0 O
-1 ct
5
16 N
-3 ov
0
o1 No
-1 v
5
16 De
-3 c
1
01 De
-1 c
5
16 J a
-3 n
01 1 J a
-1 n
5
16 Fe
-2 b
8
Fe
b
20
01
16
Month of the year
Rainfall (mm);
Mean maximum temperature in degrees Celsius (right)
123
Mean maximum temperature in degrees
Celsius
120
-1
5
Rainfall in mm per fortnight
February 2005
APPENDIX TABLES
Appendix Table 1. Experimental design for experiment 1
Animals that were used
Feeding period
Achan
Nalugya
Nakazibwe
Sanyu
1
Call¥
Cent
Desm
Ctrl
2
Cent
Desm
Ctrl
Call
3
Desm
Ctrl
Call
Cent
4
Ctrl
Call
Cent
Desm
¥
Treatments – Each animal received each treatment once
Treatment diets were as follows:
Call – P. purpureum fed ad libitum + 2.7 kg DM of dairy meal + 2.7 kg DM Calliandra
Cent – P. purpureum fed ad libitum + 2.7 kg DM of dairy meal + 2.7 kg DM Centrosema
Desm – P. purpureum fed ad libitum + 2.7 kg DM of dairy meal + 2.7 kg DM Desmodium
Ctrl – P. purpureum fodder fed ad libitum + 2.7 kg DM of dairy meal (control).
Appendix Table 2. Changes in OM concentrations as affected by legume
supplementary feeding to dairy cattle offered P. purpureum basal diet
Faecal OM
Supplements
Manure OM
Change in OM content
------------------------- g kg-1 DM -------------------------
Calliandra calothyrsus
873.96
813.03
-60.93
Centrosema pubescens
878.28
778.65
-99.63
Desmodium intortum
880.91
807.19
-73.72
Control
879.09
771.54
-107.55
----
----
56.55
LSD (0.05)
124
Appendix Table 3. Changes in total N concentrations as affected by legume
supplementary feeding to dairy cattle offered P. purpureum basal diet
Faecal N
Supplements
Manure N
Change in N content
------------------------- g kg-1 DM -------------------------
Calliandra calothyrsus
16.90
17.08
+0.18c
Centrosema pubescens
16.79
15.39
-1.40ab
Desmodium intortum
14.49
14.44
-0.05bc
Control
16.30
14.49
-1.81a
LSD(0.05)
----
----
1.44
Appendix Table 4. Changes in total P concentrations as affected by legume
supplementary feeding to dairy cattle offered P. purpureum basal diet
Faecal P
Supplements
Manure P
Change in P content
------------------------- g kg-1 DM -------------------------
Calliandra calothyrsus
6.06
3.04
-3.02b
Centrosema pubescens
6.71
2.75
-3.96a
Desmodium intortum
5.73
2.34
-3.39ab
Control
7.12
3.51
-3.61ab
LSD(0.05)
----
----
0.69
Appendix Table 5. Changes in total K concentrations as affected by legume
supplementary feeding to dairy cattle offered P. purpureum basal diet
Faecal K
Supplement
Manure K
Change in K content
------------------------- g kg-1 DM -------------------------
Calliandra calothyrsus
20.44
10.68
-9.76b
Centrosema pubescens
18.04
10.52
-7.52bc
Desmodium intortum
18.63
12.42
-6.21c
Control
24.44
10.72
-13.72a
LSD(0.05)
----
----
2.36
125
Appendix Table 6. Changes in pH as affected by legume supplementary feeding to dairy
cattle offered P. purpureum basal diet
Supplements
Faecal pH
Manure pH
Increase in pH
Calliandra calothyrsus
6.56
8.28
+1.7
Centrosema pubescens
6.90
8.24
+1.3
Desmodium intortum
6.48
8.43
+2.0
Control
6.58
8.29
+1.7
Appendix Table 7. Changes in OM concentrations as affected by faecal storage
methods
Faecal OM
Treatments
Manure OM Change in OM content
---------------------- g kg-1 DM ----------------------------
Pit and soil cover (T1)
878.06
798.53
-79.53ab
Pit and polythene (T2)
878.06
839.83
-38.23b
Pit and not covered (T3)
878.06
777.52
-100.54a
Piled on flat ground (T4)
878.06
754.53
-123.53a
----
----
56.55
LSD(0.05)
Appendix Table 8. Changes in total N concentrations as affected by faecal storage
methods
Faecal N
Treatments
Manure N
Change in N content
--------------------- g kg-1 DM ------------------------
Pit and soil cover (T1)
16.12
14.50
-1.62a
Pit and polythene (T2)
16.12
15.02
-1.10a
Pit and not covered (T3)
16.12
17.20
‡
Piled on flat ground (T4)
16.12
14.69
-1.43a
----
----
1.44
LSD(0.05)
126
1.08b
Appendix Table 9. Changes in total P concentrations as affected by faecal storage
methods
Faecal P
Treatments
Manure P
Change in P content
--------------------- g kg-1 DM ------------------------
Pit and soil cover (T1)
6.40
2.15
-4.25a
Pit and polythene (T2)
6.40
2.66
-3.75a
Pit and not covered (T3)
6.40
3.37
-3.03b
Piled on flat ground (T4)
6.40
3.45
-2.95b
LSD(0.05)
----
----
0.69
Appendix Table 10. Changes in total K concentrations as affected by faecal storage
methods
Faecal K
Treatments
Manure K
Change in K content
--------------------- g kg-1 DM ------------------------
Pit and soil cover (T1)
20.38
11.27
-9.11b
Pit and polythene (T2)
20.38
13.54
-6.84b
Pit and not covered (T3)
20.38
12.10
-8.28b
Piled on flat ground (T4)
20.38
7.43
-12.95a
----
----
2.36
LSD(0.05)
Appendix Table 11. Changes in pH as affected by faecal storage methods
Treatments
Faecal pH
Manure pH
Increase in pH
Pit and soil cover (T1)
6.63
8.39
+1.8
Pit and polythene (T2)
6.63
8.34
+1.7
Pit and not covered (T3)
6.63
8.26
+1.6
Piled on flat ground (T4)
6.63
8.26
+1.6
127
Appendix Table 12. Concentrations of NH4-N in faeces and composted cattle manure
Supplements
Faecal NH4-N content
Manure NH4-N content
---------------------------- g kg-1 -----------------------Calliandra calothyrsus
5.07
0.48
Centrosema pubescens
5.02
0.44
Desmodium intortum
5.25
0.48
Control
3.46
0.53
128