ISRAEL JOURNAL OF
VETERINARY MEDICINE
PERFORMANCE, CARCASS CHARACTERISTICS, HAEMATOLOGICAL
AND HISTOPATHOLOGICAL STUDIES OF BROILERS FED MUCUNA
(MUCUNA UTILIS) BEAN MEAL BASED DIETS
Iyayi E.A.1, Taiwo V.O.2* and Fagbohun A.O.1
Departments of 1Animal Science and 2Veterinary Pathology,
University of Ibadan, Ibadan. Nigeria.
*Author for correspondence. Email: victaiwo52@yahoo.com
Abstract
One hundred and sixty day-old broiler chicks were randomly divided into four
groups of 40 chicks and placed on dietary treatments composed of graded (0, 333, 667
and 1000g/kg) replacements of soybean meal by mucuna (Mucuna utilis) bean meal
(MBM). Feed consumption and body weight gains of birds on the 667 and 1000g/kg
KBM were significantly (p<0.05) reduced. There was a linear relationship between
feed consumption and body weights and a negative linear relationship between these
parameters and increase in MBM level. For every 7.40 unit increase in MBM level,
the weight of the birds decreased by 1gm. The value of efficiency of feed utilization
had positive linear and quadratic relationships with increased MBM indicating that
increased MBM caused lesser efficiency of utilization and conversion of the high
MBM diets by the birds.
There was a linear increase in the weights of the liver, small intestines and spleen by
1gm with 7, 19 and 3% increase in the level of MBM in the diets, respectively.
Packed cell volume (PCV) and red blood cell (RBC) counts had negative significant
(p<0.05) linear relationship with increased level of MBM. There was a unit decrease
in PCV and RBC counts with a 1.90 and 0.17 unit increase in mucuna in the diet; an
indication of the susceptibility of red blood cells to destruction due to mucuna
inclusion in diets at levels over 333g/kg. There were no significant lesions in the air
sacs, blood vessels and hearts of birds fed with control diet and those with up to
667g/kg MBM replacement. Birds on the 667 and 1000g/kg diets had significant (P<
0.001) liver, splenic and renal lesions.
Introduction
Prices of plant protein ingredients for livestock feeds have been on the increase in
Nigeria. This has resulted in the increasing cost of livestock production and
consequent increase in the cost of livestock products. The need to find alternative and
cheaper ingredients to replace the expensive ones is inevitable since cost of feed
accounts for 70-80% of the cost of poultry production in the country (1,2).
Mucuna (Mucuna utilis), a tropical legume has been reported to be able to grow in
moderately humid to dry areas and on a variety of soils including poor or sandy soils.
Being a vigorous legume, it gives high seed yields (3). At the International Institute
for Tropical Agriculture (IITA), Ibadan, Nigeria, the crop is presently being used as a
fallow crop to restore soil fertility (4).
In addition to these agronomic potentials, the seeds have been reported to have the
potential of being utilized as a livestock feed ingredient (5,6). The nutritive value of
mucuna has been reported to be improved by soaking, germination and heat treatment
which inactivate, reduce or destroy the inherent anti-nutrient components (7). As yet,
its use in livestock feeding as a plant protein source has not been fully exploited. This
study reports the effects of feeding mucuna bean meal (MBM- based diets on the
performance,carcass characteristics, haematological and histopathological
characteristics of broilers.
Materials and Methods
Experimental Design
Mature mucuna bean seeds were obtained from the IITA, Ibadan, Nigeria. They
were roasted for 10 minutes and then milled to obtain a meal of the same coarse
degree as soybean meal. The meal was incorporated into the starter and finisher diets
at 333, 667 and 1000g/kg in place of soybean in the meal. The dietary and
approximate compositions of the broiler starter and finisher diets are shown in Table
1.
One hundred and sixty day-old broiler chicks were obtained from a local commercial
poultry farm. After routine vaccination against Newcastle disease and infectious
bursal disease and other required veterinary care, the birds were allocated to 20 pens
each with eight birds. Each of the diets was randomly allocated to five pens. The birds
were fed in groups of eight and records of feed intake were used to compute avearge
weekly feed consumption per bird. The birds were given feed and water ad libitum.
Between day 1 and 28 (starter phase) the birds were given the starter diet.
At the end of the the 28th day, the birds were weighed. Thereafter, their diets were
switched to finisher diets. They were then fed for another four weeks (finisher phase)
till day 56. Weekly records of body weights (batch-weighing of each replicate for the
first three weeks, thereafter individually), efficiency of feed utilization and feed
conversion ratio were measured as indices of growth performance of the birds. At the
end of the experiment the remaining birds in all the treatments were euthanized.
Proximate composition of the mucuna bean meal and the experimental diets were
carried out according to the procedure of AOAC (1990). The crude protein of the
feeds was determined by the Kjeldahl method as described by AOAC (8). The crude
protein value was estimated as 6.25 multiple of the nitrogen value. Crude fiber
determination was carried out using the trichloroacetic acid (TCA) method. One gram
of the feed sample was digested and refluxed with 100ml TCA solution followed by
filtration.
The recovered residue was then charred and ashed at 600oC for 30 minutes. The
difference in weight between residue and ash multiplied by 100 gave the percentage
crude fiber of the feed sample. Energy was determined using the bomb calorimeter.
One gram of the feed sample was pelleted and oven-dried at 103oC for 24 hours. The
samples were then re-weighed and bombed. Values of deflections obtained were used
to calculate the metabolizable energy of the diets.
Table 1: Dietary composition of experimental starter and finisher broiler diets
Starter diets
Finisher diets
1
2
3
4
1
2
3
4
Maize
460
460
460
460
400
400
400
400_
Cassava
50
50
50
50
-
-
-
-
Wheat bran
100
100
100
100
250
250
250
250
Maize bran
-
-
-
-
80
80
80
80_
60
60
60
60
-
-
-
-
Groundnut Meal
110
110
110
110
70
70
70
70
Soybean meal
180
120
60
-
150
100
50
-
-
60
120
180
-
50
100
150
25
25
25
25
22.
22.5
22.5
15.
15.5
15.5
Ingredients
(g/kg)
Brewer’s dried
grains
Mucuna bean
meal
Fish meal
22.
5
Bone meal
60
60
60
60
5
15.
5
5
Oyster shell
5.0
5.0
5.0
5.0
8.0
8.0
8.0
8.0
Salt
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
Vit-Min Premix*
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
TOTAL
1000
100
1000
1000
210
212
100
0
100
0
100
0
100
0
0
Analyzed Nutrient
Composition (g/kg)
Protein
219
213
210
217
202
212
Crude fibre
72.20
71.
30
69.
00
67.
00
50.
58
50.
00
49.00
48.00
MEMJ/Kg
11.43
11.
44
11.
41
11.
43
11.
43
11.
42
11.43
11.44
_* Vit-Min Premix (Agricare-Mix, Pfizer Production Plc, Lagos, Nigeria) contained: Vitamin A,
12,000,000 IU; Vitamin D3 2,000,000 IU; Vitamin E 7,000IU; Vitamin B2, 4,000 mg; Nicotinic acid
15,000 mg; Calcium d-pentothenate 8,000 mg; Biotin 40mg; Vitamin B12 10mg; Mn 20,000 mg; Fe
50,000 mg; Zn 100,000 mg; Cu 10,000 mg; Iodine 750mg; Co 3000 mg
Haematological Studies
Five millilitres (ml) of blood were collected into vacutainer tubes containing ethylene
diamine tetraacetic acid (EDTA) anticoagulant from each bird on days 28 and 56 by
cardiac puncture. The following haematological parameters were determined as
described by Jain (9): red blood cell (RBC) and white blood cell (WBC) counts,
haemoglobin (Hb) concentration,packed cell volume (PCV), mean corpuscular
haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC).
Carcass evaluation and postmortem examination
On the last day of the experiment (i.e. day 56), the birds were fasted overnight,
weighed the following morning prior to euthanization. The birds were defeathered
completely using warm water and then re-weighed to obtain plucked carcass weights.
They were then decapitated and eviscerated and weighed again to obtain the
eviscerated weights. All body organs were separated and weighed to obtain their fresh
weights, as described by Summers et al. (10). The organs included the air sacs, liver,
kidneys, spleen, gizzards, and small and large intestines. The weights of the organs
were expressed as percentage proportion of live weights. During processing, the
carcases were observed forgross pathological changes. Trimmed sections were taken
and fixed in Bouin’s fluid for 6 hours and then in 10% phosphate-buffered formalin
for another 24 hours. They were thereafter routinely processed for histopathological
examinations by embedding in wax, sectioned at 5µm onto grease-free glass slides,
stained with haematoxylin and eosin and examined microscopically (Olympus,
Japan).
Statistical analysis
All data collected were analysed statistically on a pen basis for significance due to
treatment effect using the SAS (11) General Linear Model. Contrast between means
was tested using linear polynomials (12) and data on the histological lesions were
analyzed using the Chi-square test.
Results
Results of the chemical composition of mucuna bean meal are presented in Table 2.
Amino acid profiles ofsoyabean and mucuna bean meals are presented in Table 3.
Mucuna has protein content of 353.9g/kg DM and a crude fibre content of 77.3g/kg
DM. Its carbohydrate fractions constitute about 478.8g/kg DM. It has moderate
amounts of minerals especially iron, and is rich in hydrocyanic acid, tannins and
phytic acid.
Results of performance of the birds at starter and finisher phases are presented in
Table 4. There was a significant reduction (p<0.05) in feed consumption with an
increased MBM level in the diet. This reduction was more pronounced between days
28 and 56. A similar pattern was observed for the weights. Thus, there was a negative
linear relationship between feed consumption and body weight gain and increase in
mucuna bean meal levels. The birds on the control and 333g/kg mucuna diets had
significantly (p<0.05) higher body weights at both starter and finisher phases than the
birds on the other two diets. For every 7.40g/kg increase of the mucuna bean meal
inclusion level, the weight of the birds decreased by 1gm. The values of efficiency of
feed utilization had a positive linear relationship with mucuna bean meal inclusion
level. The results demonstrate that feeding broilers diets with levels of MBM
•667g/kg up to the finisher phase can produce significant lesions in the liver,
intestines and kidneys.
The results of organ weights are shown in Table 5. There was no significant effect
(p>0.05) on the weights of the gizzards, heart, air sacs, large intestines and caeca.
However, the weights of liver, small intestines, and spleen had a significant (p<0.05)
linear relationship with MBM level in the diet. The weights of the organs increased by
1gm linearly, with 78, 19 and 3% increase in the MBM level in the diet respectively.
The results of the haematological parameters and indices measured are shown in
Table 6. Only the PCV and RBC counts had negative, significant (p<0.05) a linear
relationship with increased level of mucuna. There was a unit decrease in PCV and
RBC counts with 1.90 and 0.17 unit increases in Mucuna in the diets at levels over
333 g/kg. Table 7 shows the results of the chi-square tests of the graded histological
lesions observed in the organs of birds in each dietary treatment. Pulmonary
congestion and oedema, enteritis and villus collapse and cardiac muscle degeneration
were all significantly present in birds on the 1000g/kg MBM diets. The birds on the
667 and 1000g/kg MBM diets had significant (p<0.05) fatty degeneration, hepatic
necrosis, cellular infiltration, mild portal fibrosis, splenic lymphoid necrosis,
macrophage proliferation and lymphophagocytosis. The 333, 667 and 1000g/kg MBM
diets had significant (p<0.05; p<0.01) effects, respectively on renal congestion,
tubular nephrosis, protein and urate casts in kidney tubules.
Table 2: Chemical composition of Mucuna bean meal
Component
Mucuna bean meal
Proximate Composition (g/kg DM)
Moisture
98
Dry matter
903
Crude Protein
354
Crude fibre
77
Ether extract
32
Ash
36
Nitrogen free extract
479
Major minerals (g/kg DM)
Potassium
14
Calcium
10
Magnesium
19
Phosphorus
8
Trace minerals (mg/Kg DM)
Zinc
13
Manganese
27
Iron
129
Copper
25
Anti-nutritional factors (mg/kg DM)
Hydrocyanic acid (HCN)
82
Tannins
21
Phytic acid
21
Table 3: Essential amino acid content of Soybean meal and Mucuna bean meal
(% crude protein).
Soybean meal
Amino acid
5.80
7.20
Arginine
2.85
4.10
Glycine
2.03
2.50
Histidine
4.72
4.30
Isoleucine
7.09
7.60
Leucine
6.22
5.60
Lysine
1.50
1.10
Methionine
4.23
4.80
Phenylalanine
4.08
3.80
Threonine
1.44
1.60
Tryptophan
5.21
4.40
Valine
Mucuna
bean meal
Table 4: Performance of 8-week old broilers on experimental diets
Table 5: Weight of cut parts and organs of birds (as percentage of live weight)
on experimental diets at the end of the finisher phase.
Table 6: Haematology of birds fed diets with graded levels of MBM
substitution for soybean meal at the end of the finisher phase.
Table 7: Result of chi-square analyses of histological lesions in organ of birds
fed graded levels of MBM substitution for soybean meal at the end of the finisher
phase.
Discussion
In the present study, the consumption of >333g/kg MBM-based diets by broilers led
to reduced feed intake and efficiency of feed utilization. Reduced feed consumption
was responsible for the reduced weights obtained. This was an indication of less
efficient utilization of the diets with increasing levels of mucuna bean meal. Reduced
feed intake due to cyanide, L-dopa, tannins and other antinutritional factors in the
mucuna impacted negatively on the growth of the birds. Similar results have been
reported by Flores et al., (13) who fed mucuna-based diets to pigs and reported that
animals on the mucuna-based diets consumed approximately 2.2 times less feed and
therefore nutrients, much below their daily requirements which resulted in reduced
weights. Emenalom et al., (14) also reported that pigs fed a 15% raw mucuna-based
diet had significantly reduced feed intake, weights and poorer feed conversion ratio
compared to animals on the control diet. Results of lower feed consumption and
weight gain in broilers fed diets in which raw mucuna was incorporated at 10% have
been reported by Del Carmen et al., (15). L-dopa, cyanide, tannins and trypsin
inhibitors were blamed for the poorer performance of the birds. In this study, these
antinutritional factors were potent agents that caused reduced feed consumption in the
birds on the mucuna-based diets and therefore reduced intake of nutrients. As the
levels of mucuna in the diet increased, so were the feed consumption and weights of
the birds reduced. Results of the present study show the MBM to be moderately high
in tannins, phytic acid and hydrocyanic acid. Hydrocyanic acid was reported to induce
weight loss in animals (16) by the use of the sulphur-amino acids to detoxify the
cyanide to thiocyanate. Under this condition, fewer amino acids are available for
incorporation into muscle mass. The amino acid profile of the MBM compared to that
of SBM shows it to lack some of the amino acid and fairly comparable to SBM in
lysine, methionine and phenylalanine. Continued consumption of the high MBM diets
up to the finisher phase put an increased pressure on the birds of the need for amino
acids for detoxification of the anti-nutrients thereby sparing only a little for growth.
Sulphur-containing amino acids have been implicated in the detoxification of cyanide
(17). The ability of the birds to efficiently utilize the high MBM feeds was therefore
significantly lowered as shown by their significant reduction in weight gain. The
linear relationship between mucuna level in the diets and observed values of
efficiency of feed utilization showed the inability of the birds to efficiently utilize and
convert the mucuna bean meal diets to body mass. The reduced feed intake of birds on
diets 3 and 4 became more pronounced at the finisher phase. This significantly
affected the birds on these diets, and for every 7.40g/kg increase in mucuna in the
diet, the weight of the birds was reduced by 1gm. This same effect was noticeable in
the organs.
Apart from the cyanide content in the diets, inclusion levels of 667 and 1000g/kg
MBM at a tannin concentration of 20.5g/kg DM of MBM would give total available
tannin concentrations of 1.37 and 2.05g/kg, respectively. Such tannin levels often
encountered in the feeding of livestock with mucuna seed induce poor performance in
birds (18,19). Earlier findings by Griffiths (20) of the lethality of feeding of high
tannin levels in poultry diets support these present findings.
Other anti-nutritional factors in mucuna like L-3,4-dihydroxyphenylalanine (L-dopa),
and lectins (though not reported in our study) also induce poor growth through
reduced feed consumption and toxic effects. Afolabi et al.,(21) and Ravindran and
Ravindran (5) reported that L-dopa intoxication associated with the consumption of
mucuna beans is related to their L-dopa content. The anti-nutritional factors, lectins
and L-dopa have been implicated in nutritional disorders in monogastric animals
associated with their consumption. Grant (22) reported that lectins exert their
deleterious anti-nutritional effects through reduced nutrient absorption following
extensive structural and functional disruption of the intestinal microvilli. Lectins are
also reported to reduce the feed intake of animals (23) L-dopa is potentially toxic on
consumption, not heat-labile and not easily detoxified. Afolabi et al., (21), Ravindran
and Ravindran (5) reported that L-dopa is the biggest obstacle confronted in the
utilization of mucuna beans. The mechanism of action of L-dopa is possibly close to
that of most anti-nutritional factors naturally occurring in legumes. These factors exert
their deleterious effects through depressed nutrient absorption as a result of extensive
structural and functional disruption of intestinal microvilli, depicted as small intestinal
villus collapse in this study. They could have led to shedding of brush-border
membranes and decreased villus length with consequent reduction in the surface area
for absorption in the small intestine as suggested by Lorenzson and Olsen (24). The
significant changes in the weight of the small intestines at the finisher phase with
progressive increase in the level of MBM support the view that the anti-nutritional
factors of mucuna had marked effect on the anatomy of the digestive tract of the birds
as they grew older. The difference in the observed effect on the birds’ performance
between the starter and finisher phases is due to the accumulative or chronic effect of
the anti-nutritional factors in the diets that the birds were given. Similar observations
with broilers given jack bean diets have been reported by Leon et al., (25) and
Ologhobo et al., (23).
There was moderate to severe anaemia and leucopenia (not significant) as the SBM
replacement by MBM reached 1000g/kg. The observed anaemia in the birds, shown
as decreases in PCV levels and RBC counts, indicated that red blood cells were
susceptible to destruction by the anti-nutrients, especially by cyanide (in hydrocyanic
acid) and other factors in mucuna. Cyanide inhibits the detachment of haem from
haemoglobin leading to impairment of erythropoiesis (26). It also binds with
haemoglobin forming cyanmethaemoglobin, from which oxygen is not easily
released; causes the inactivation of cytochrome oxidase and inhibition of oxidative
phosphorylation in red blood cells leading to ineffective oxygen use; and impairment
of cellular respiration leading to tissue necrosis, especially of the brain, liver and heart
(27). Damage to organs such the liver, kidneys and bone marrow will affect the
production and effective use of erythropoietin leading to impaired erythropoiesis (28).
The RBC counts, for instance was markedly reduced with every 17g/kg increase in
the mucuna level. This accounts for the significant reduction in efficient digestion of
the diets and the mortality of birds recorded with the high mucuna diets, especially for
those given 1000g/kg mucuna. The anaemia that developed predisposed the birds to
the lesions observed at postmortem. The severity of these lesions increased with
increasing levels of mucuna in the diet. The significant pulmonary congestion,
intestinal villus collapse and cardiac degeneration of birds on the highest MBM diet
indicated the poor health of the birds. However, significant liver, splenic and renal
complications were observed at much lower levels of MBM in the diets, suggesting a
more chronic predisposition, anaemia, more morbidity, susceptibility to secondary
infections, and economic losses due to poor weight gain and cost of medication. The
liver and kidney function in the detoxification and excretion of most toxic materials
from the body (29), hence they were the most affected organs in the broilers fed
>333g/kg MBM in this study.
In conclusion, this study has shown that while less than 333g/kg processed mucuna
bean meal can be conveniently used to replace soyabean meal in broiler rations, it is
not expedient to go above this level. This is because for every 6g/kg increase in the
level of mucuna in the diet the efficiency of utilization of the feed and the weight of
the bird were reduced significantly. The search for novel processing methods that will
drastically reduce the levels of tannins and other anti-nutritional factors in Mucuna
utilis should be encouraged.
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