COLLEGE OF AGRICULTURE AND NATURAL RESOURCE SCIENCES
DEPARTMENT OF ANIMAL SCIENCE
DEBRE BERHAN UNIVERSITY
COURSE GUIDE BOOK FOR:
FEED PRODUCTION & ANIMAL NUTRITION
Prepared By: Ayele Negash and Aynadis Ababu
Program: BSc in Animal Science
March, 2023
Debre Berhan University, Ethiopia
1. PRINCIPLE OF ANIMAL NUTRITION
Learning Outcomes:
Upon successful completion of this course, students should be able to:
 Know the characteristics and functions of basic nutrients;
 Understand the similarities and differences among digestive systems of farm animals;
 Discuss processes of digestion, absorption and metabolism of nutrients; and
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
Understand nutritional deficiencies and toxicities related to the nutrients, and metabolic
disorders.
Introduction to nutrition
Nutrient is any substance absorbed by an organism from its external environment and used in the
metabolism. It is source of materials needed for growth, maintenance, and reproduction and
production purpose. It includes: Water, Carbohydrate, Proteins, Lipids, Minerals and Vitamin.
A). Water - Often overlooked and not considered as a nutrient when formulating diets for animals,
but extremely important.
B). Carbohydrates - Hydrates of carbon formed by combining CO2 & H 2O (photosynthesis).
The primary component found in animal feeds.
C). Protein - Found in the highest concentration of any nutrient (except water) in all living
organisms and animals. All cells synthesize proteins, and life could not exist without protein
synthesis.
D). Lipids - Organic compounds that are characterized by the fact that they are insoluble in water,
but soluble in organic solvent (benzene, ether, etc.)
E). Minerals - Inorganic, solid, crystalline chemical elements that cannot be decomposed or
synthesized by chemical reactions. f) Vitamins - Organic substances that are required by animal
tissues in very small amounts.The last group of dietary essentials to be recognized
Water
It is vital to the life of the organism that the water content of the body be maintained. An animal
will die more rapidly if deprived of water than if deprived of food. Water functions in the body as
a solvent in which nutrients are transported about the body and in which waste products are
excreted. Many of the chemical reactions brought about by enzymes take place in solution and
involve hydrolysis. Because of the high specific heat of water, large changes in heat production
can take place within the animal with very little alteration in body temperature. Water also has a
high latent heat of evaporation, and its evaporation from the lungs and skin gives it a furtherrole
in the regulation of body temperature. The animal obtains its water from three sources: drinking
water, water present in its food, and metabolic water, this last being formed during metabolism by
the oxidation of hydrogen-containing organic nutrients. The water content of foods is variable and
can range from as little as 60 g/kg in concentrates to over 900 g/kg in some root crops. Because of
this great variation in water content, the composition of foods is often expressed on adry matter
basis, which allows a more valid comparison of nutrient content.
There is no evidence that under normal conditions an excess of drinking water is harmful, and
animals normally drink what they require. Body water content of the animal body varies
considerably; the newborn animal contains 750–800 g/kg water but this falls to about 500 g/kg in
the mature fat animal. It is influenced over the long term by the age of the animal and the amount
of fat in the tissues. Water content is highest in fetuses and in newborn animals.
Water Requirement
Carbohydrates
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Carbohydrates (also called saccharides) are on the basis of mass the most abundant class of
biological molecules on Earth. Carbohydrates consumed by animals serves as source of energy, as
a reserve in the form of fat mainly, and also glycogen into which it is readily transformed.
Functions of Carbohydrates in genera
1. Carbohydrates are the main sources of energy in the body.
2. Store energy (starch and glycogen).
3. Excess carbohydrate is converted to fat.
4. Carbohydrates are linked to many proteins and lipids
5. Structural basis of many organisms: Cellulose of plants; exoskeleton of insects, cell wall of
microorganisms, mucopolysaccharides as ground substance in higher organisms.
6. Acts as cell surface marker.
When one sees the carbohydrate in plant tissues, basically they are found in two forms.
i) Structural carbohydrate- mainly cellulose, in terms of quantity cellulose comprise the largest
proportion of carbohydrates in plants.
ii) Reserve carbohydrate- starch is the basic reserve carbohydrates while glycogen is for animals.
Glucose is the basic building structure for forming complex carbohydrates. Many carbohydrates
have the same empirical formula (CH20)n where n>3, the definition is not strictly correct, and
there are exceptions for this definition. This includes:
a) It is possible that other chemical compounds which are not carbohydrates could have the same
ratio of the elements C, H, 0. Example: Acetic acid is not CH20 but has a formula of C2H402
Lactic acid C3H603 (CH3.CHOH.COOH)
b) There is a possibility of the carbohydrate without having the elements in the indicated ratio
Example: Rhamnose C6H12O5, Deoxyribose C5H10O4
Classification of carbohydrates
Carbohydrates are usually divided into 2 major groups according to their chemical nature. 1.
Sugars 2. Non- sugar
1. Sugar
These are group of carbohydrates containing less than 10 monosaccharide residues. These are
groups of carbohydrates which are soluble in water and sweet to test. These things differentiate
sugars form non-sugars which contain >10 monosaccharides units, in their structure; insoluble in
water and not show sweet taste. The sugars include:A. Monosaccharides
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These are the simplest sugar and are building block of carbohydrates. This could be divided based
on the number of carbon atoms present in the molecule as:
❖ Trioses (C3H6O3) - smallest monosaccharide’s which certain 3 carbon atoms
❖ Tetroses (C4H8O4) - contain 4 carbon atoms
❖ Pentoses (C5H10O5) - contain 5 carbon atoms
❖ Hexoses (C6H12O6)- contains 6 carbon atoms
❖ Heptoses (C7H14O7) - contains 7 carbon atoms
The trioses and tetroses occur as intermediates in the metabolism of other carbohydrates.
Monosaccharides may be linked together, with the elimination of one molecule of water at each
linkage, to produce di, tri-, or tetra-or polysaccharides containing two, three, four or many
monosaccharide units respectively.
B. Oligosaccharides
The name comes from Greek oligos means a few and is frequently used to include all sugars other
than the monosaccharides. Oligosaccharides contain carbohydrates containing 2-10
monosaccharide units. Oligosaccharides could be divided into different groups based on the
number of monosaccharide units as opposed to the number of carbon atom as in the case of
monosaccharides.
Disaccharides - oligosaccharides with 2 monosaccharide units
Trisaccharides - oligosaccharides with 3 monosaccharide units
Tetrasccharides - oligosaccharides with 4 monosaccharide units
2. Non-sugars
These contain greater than 10 monosaccharide units. Sugars have less molecular weight than nonsugars. The non-sugars are also called polysaccharides or glycans - (poly means many). So they
are polymers of monosaccharide units. We have two groups of polysaccharides based on the type
of monosaccharide units present in the chain.
a. Homopolysaccharides (Homoglycans)
Homo means same, hence these are polysaccharides which contain only a single type of
monosaccharide units or these polysaccharides result to one type of monosaccharide on hydrolysis.
Example, Glucans (glucosan) - homopolysaccharides made of many glucose units attached
together like Starch, glycogen, cellulose, dextrins, Fructans (Fructosan)- made up of many fructose
units like inulin, levan.
b. Hetropolysaccharides (Hetroglycans)
All polysaccharides which on hydrolysis yield mixture of monosaccharides. Therefore, these
polysaccharides are made of greater than one type of monosaccharides. Non-sugars also contain
complex carbohydrates which are ill-defined group of compounds which contain carbohydrates in
combination with non- carbohydrates molecules. They include the glycolipids and glycoprotein.
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Proteins
Proteins are complex organic compounds of high molecular weight. Proteins are found in all living
cells, where they are intimately connected with all phases of activity that constitute the life of the
cell. Plant proteins differ from each other and from animal proteins. Proteins are basically made
of building blocks called amino acids, which is one structurally unifying factor of proteins.
Proteins are mainly found in active tissues in plants and animals like leaves, shoots, and muscle.
In common with carbohydrates proteins contain carbon, hydrogen and oxygen but in addition they
also contain nitrogen. Most proteins also contain sulfur and a few contains phosphorous and iron.
The sequence of amino acids along the polypeptide chain of a protein is called the primary structure
of the protein. The secondary structure of proteins refers to the conformation of the chain of amino
acids resulting from the formation of hydrogen bonds between the amino and carbonyl groups of
adjacent amino acids. Folding of the chain gives the tertiary structure. The quaternary structure
refers to the configuration of those proteins with more than one polypeptide
Classification of proteins
Proteins may be classified into two main groups: simple proteins and conjugated proteins.
1. Simple proteins
These proteins produce only amino acids on hydrolysis. They are subdivided into two groups,
fibrous and globular proteins, according to shape, solubility and chemical composition.
A. Fibrous proteins
These proteins, which in most cases have structural roles in animal cells and tissues, are insoluble
and are very resistant to animal digestive enzymes. They are composed of elongated filamentous
chains joined together by cross-linkages. The group includes collagens, elastin and keratins.
Collagens are the main proteins of connective tissues and constitute about 30 per cent of the total
proteins in the mammalian body. Elastin is the protein found in elastic tissues such as tendons and
arteries. The polypeptide chain of elastin is rich in alanine and glycine and is very flexible. It
contains cross-links involving lysine side chains, which prevent the protein from extending
excessively under tension and allow it to return to its normal length when tension is removed.
Keratins are classified into two types. The α-keratins are the main proteins of wool and hair. The
β-keratins occur in feathers, skin, beaks and scales of most birds and reptiles. These proteins are
very rich in the sulphur- containing amino acid cysteine; wool protein, for example, contains about
4 percent of sulphur.
B. Globular proteins
Globular proteins are so called because their polypeptide chains are folded into compact structures.
The group includes all the enzymes, antigens and those hormones that are proteins. Their first
subgroups, albumins, are water- soluble and heat-coagulable and occur in milk, the blood, eggs
and many plants. Histones are basic proteins that occur in cell nuclei, where they are associated
with DNA. They are soluble in salt solutions, are not heat- coagulable, and on hydrolysis yield
large quantities of arginine and lysine. Protamine are basic proteins of relatively low molecular
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weight, which are associated with nucleic acids and are found in large quantities in the mature
male germ cells of vertebrates. Globulins occur in milk, eggs and blood, and are the main reserve
protein in many seeds.
2. Conjugated proteins
Conjugated proteins contain, in addition to amino acids, a non-protein moiety termed a prosthetic
group. Some important examples of conjugated proteins are glycoproteins, lipoproteins,
phosphoproteins and chromoproteins. Glycoproteins are proteins with one or more heteroglycans
as prosthetic groups. In most glycoproteins the heteroglycans contain a hexosamine, either
glucosamine or galactosamine or both; in addition, galactose and mannose may also be present.
secretions, which act as lubricants in many parts of the body. The storage protein in egg white,
ovalbumin, is a glycoprotein.
They can be classified into five main categories in increasing order of density: chylomicrons, verylow-density lipoproteins (VLDL), low-density lipoproteins (LDL), intermediate-density
lipoproteins (IDL) and high-density lipoproteins (HDL).
Chromoproteins contain a pigment as the prosthetic group. Examples are haemoglobin and
cytochromes.
Amino acids
Proteins are polymers of amino acids. Amino acids are produced as hydrolytic end products, where
proteins are heated with strong acids, alkalis or when they are acted upon by certain enzymes.
There are a number of amino acids identified the highest figure mentioned in books is 200 amino
acids. Out of these only 20 amino acids are commonly found as components of proteins and hence
nutritionally important. Amino acid are characterized by having a basic nitrogenous group,
generally an amino group (-NH2), and an acidic carboxyl group (-COOH).
To study the different amino acids that constitute the different proteins classification is developed
where by amino acids are divided into 3 groups depending on their chemical structure or a series
of organic compounds in which they belong.
I. Aliphatic amino acids - this contain straight chain amino acid.
II. Aromatic amino acids - these are amino acids containing benzene ring somewhere in their
structure. Example, phenylalanine, tyrosine, diiodotyrosine, thyroxine.
III. Heterocyclic amino acids - are amino acids not fit in any one above. Example, Histidine,
proline, hydroxyproline, tryptophan. Aliphatic amino acids are the amino acids which contain most
of the nutritionally important amino acids.
These groups can be subdivided into:
A. Neutral amino acids - are amino acids which contain equal no of the amino and carboxylic
group. Since this group contain one NH2 & one COOH, they are called monoaminomonocarboxylic acids. This comprises the largest number of amino acids. Example, glycine,
alanine, serine, valine, leucine. Isoleucine and threonine.
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B. Acidic amino acids (monoamino-dicarboxylic acids) - These are amino acids that contain
more number of carboxylic than amino group and hence the acidic properly is more. Example,
Aspartic acid, glutamic acid.
C. Basic amino acids (Diamino-monocarboxylic acids) - These amino acids has more amino
than carboxylic group and hence dominant basic character. Example, Arginine. Lusine. Citrulline.
D. Thio amino acids - these are sulfur containing amino acids like cysteine, cystine, methionine.
Plants and many microorganisms are able to synthesise proteins from simple nitrogenous
compounds such as nitrates, so can synthesise all the 20 amino acids.
Certain amino acids could be synthesized in the animal body from others while a number of them
cannot be synthesized in the animal body and these are referred to as indispensable or essential
amino acids so must be included in the diet. The others which are not obligatory and can be
synthesised within the body are called dispensable or non-essential amino acids.
The chicks require in their diet the ten amino acids plus glycine as the 11th essential amino acid.
Dispensable amino acids include: Cysteine, Tyrosine, Glutamic acid, Alanine, Aspartic acid,
Serine, Proline, Cystine, Citrulline, Hydroxyproline.
Peptides are built up from amino acids by means of a linkage between the α- carboxyl of one amino
acid and the α-amino group of another acid. This type of linkage is known as the peptide linkage,
a dipeptide has been produced from two amino acids.
Lipids
Lipids are group of substances found in plant and animal tissues, insoluble in water but soluble in
common organic solvents such as benzene, ether, chloroform, ethanol which is the specific
character of lipids. These are basically made up of the elements carbon, hydrogen and oxygen, but
quantity of oxygen found in basic lipid structures is lower than that found in carbohydrates. Lipids
can be divided into two basic groups
1. Glycerol based lipids: are lipids having glycerol unit in their structure
2. Non glycerol based lipids: are lipids that do not contain glycerol in their structure.
Glycerol based lipids are divided further into:
a. Simple lipids: these have one group of compounds that is fat & oils.
b. Compounds lipids: these are of two types
i. Glycolipids: are lipids that contain sugar attached to the lipidmolecule. It can be glucolipids that
contain glucose attached to the lipid or galactolipids that contain galactose attached to lipid
molecule.
ii. Phospholipids: are lipids containing phosphoric acid or phosphorous attached and are of two
types, lecithins and cephalins. Lipids play different roles in the animal body. They act as electron
carriers, substrate carriers in enzymatic reaction, as components of biological membranes & stores
of energy.
Functions of Lipids
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√ As an energy source
√ Source of steroid hormones are critical intercellular messengers.
√ Helps in absorption of lipid-soluble vitamins (A, D,E, K)
√ Provide shock absorption.
√ Helps in insulation to heat change.
√ Adds taste & palatability to foods.
√ Acts as surfactant, detergent & emulsifying agent.
√ Give shape to the body.
Fats and oils are constituents of both plants and animals and are important sources of stored energy.
Both have the same general structure but have different physical and chemical properties. The
melting points of the oils are such that at ordinary room temperatures they are liquid and they tend
to be more chemically reactive than the more solid fats.
Fatty acids
Fatty acids are classed into two groups, which are saturated fatty acids and unsaturated fatty
acids. The difference between the two is that the saturated group contains no double bonds in their
structure, while the unsaturated fatty acids contain at least one double bond in their structure. The
common names are given while names in parentheses represent the modern chemical nomenclature
the suffix anoic refers to the saturated fattyacids, and enoic shows that the fatty acid is
unsaturated. The suffix monoenoic refers to the presence of one double bond, dienoic, trienoic,
tetraenoic four, polyenoic refers to the presence of two, three, four and many double in the fatty
acid molecule. These double bonds are reflected in the formulas for the fatty acids in that they
have smaller number of hydrogen atoms relative to the carbon atom present.
In many nutrition books linoleic, linolenic and arachidonic acids are classed as essential fatty
acids (EFA), because the lack of these fatty acids in the diet of animal especially at young stage
(calves, lamb, kids, pigs, and chicks) result to the development of deficiency symptoms.
Recent experiments recognise that the most important EFA is linoleic and if animals supplied
enough quantities of this acid the other two EFA could be synthesised from this acid. The oilseeds
are generally rich sources of linoleic acid, linseed is particularly good source of linoleic acid.
Vitamins
Vitamins are organic compounds required by the body in trace amounts to perform specific cellular
functions. They cannot be synthesized by humans, and therefore must be supplied by the diet.
Classification of vitamins
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Vitamins are two types
1. Fat soluble vitamins: are vitamins A, D, E and K
2. Water soluble vitamins: are vitamins thaimin, riboflavin, nicotinic acid, pyridoxine,
panthothenic acid, biotin, folic acid, choline and vitamin B12 and vitamin C
Water soluble vitamins
They are nine in number:
1.
Thiamine (vitamin B1)
6. Folic acid
2.
Riboflavin (vitamin B2)
7. Cobalamin (vitamin B12)
3.
Niacin (vitamin B3)
8. Pyridoxine (vitamin B6)
4.
Biotin
9. Ascorbic acid (vitamin C)
5.
Pantothenic acid
• Many of the water-soluble vitamins are precursors of coenzymes for the enzymes of intermediary
metabolism.
General characteristics
√ Vitamins are of widespread occurrence in nature, both in plant and animal worlds.
√ All common foodstuffs contain more than one vitamin.
√ The plants can synthesize all the vitamins whereas only a few vitamins are synthesized in the
animals.
√ Most of vitamins have been artificially synthesized.
√ All the cells of the body store vitamins to some extent.
√ Vitamins are partly destroyed and are partly excreted.
√ Vitamins carry out functions in very low concentrations.
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Function, Deficiency Signs & Sources of vitamins
Vitamins
Source
Actions
Deficiency symptoms
A, retinol
Fish-liver oil
Sight, epithelial tissues
Blindness, epithelial infection
D3, cholescalciferol
Fish-liver oil, sun-dried
Calcium absorption
Rickets
Muscle degeneration.
roughage
E, α-tocopherol
Green foods, cereals
Antioxidant
K, menadione
Green foods, egg yolk
Prothrombin synthesis
B1, thiamin
Seeds
Carbohydrate
Liver
damage
Anaemia, delayed clotting
and
fat Poor growth, polyneuritis
Metabolism
B2, riboflavin
Green foods, milk
Carbohydrate
and Poor
Amino
acid paralysis
growth,
curled
toe
anaemia,
poor
Metabolism
Nicotinamide
Yeast, liver, tryptophan
Hydrogen
transf
er Poor growth, dermatitis
(NAD and NADH)
B6, pyridoxine
Cereals, yeast
Amino
acid Poor growth, convulsions
Metabolism
Panthothenic acid
Folic acid
Biotin
Choline
Liver, yeast, cereals
Green
foods,
Acetate and fatty acid
Poor growth, scaly skin, goose-
Metabolism
stepping in pigs
(coenzyme A)
c
e
r
e
a
l
s
, Metabolism of single
oilseed meals
carbon compounds
Liver, vegetables
Carbon
Green
foods,
Methionine
Poor
growth,
hatchability
dioxid
e Foot lesion, hair loss
Transfer
c
e
r
e
a
l
s
, Components
of Poor growth, fatty liver, perosis
Lecithin
B12, cyancobalamin
Microorganisms, liver
C, ascorbic acid
Citrus
fruits,
Propionate metabolism
l
e
a Oxidation/reduction
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Poor
growth,
anaemia,
Reduced resistance to infection
poor
f
y
vegetables
Reactions
Minerals
These are inorganic nutrients necessary in serving the animal body in many different ways.
Minerals have many roles in addition to their catalytic role by activation of many enzymes. Other
roles of minerals include:
❖ They are building blocks of animal tissues such as constituents of bones and teeth (structural
role), and also essential for synthesis of structural proteins like the mineral sulphur.
❖ Minerals are components of organic compounds like iron hemoglobin, cobalt is vitamin B12.
❖ Minerals serve a variety of functions as soluble salts in blood and other body fluids playing role
in maintenance of osmotic relations and acid base equilibrium (elector chemical function).
An essential mineral element is restricted to minerals which have been proved to have a metabolic
role in the body.
Toxicity of minerals
Animals may be able to tolerate minerals in excess of recommended quantities; however, excess
minerals in some species can cause toxicity, even leading to death. Producers should always ensure
that minerals are given in the appropriate amount to animals. Sheep are susceptible to copper
toxicity, which can lead to death. Symptoms of copper toxicity in sheep include lethargy, anemia,
pale membranes, thirst, and jaundice. Excess of some minerals can cause weight loss and slower
rates of gain in some animals.
Digestion in monogastric mammals.
The term “monogastric” refers to the structure of the stomach. In a monogastric digestive system,
the stomach has a simple structure consisting of a single compartment. A number of species have
a monogastric digestive system, including swine, horses, dogs, rabbits, and fowl. All of the
mammals listed here have similar systems, although some minor differences do exist between
them. Fowl, however, have a digestive system that differs from the others, including organs not
found in the other species. The digestive tract can be considered as a tube extending from mouth
to anus, lined with mucous membrane, whose function is the prehension, ingestion, digestion and
absorption of food, and the elimination of solid waste material. The various parts are mouth,
pharynx, oesophagus, stomach, and small and large intestine. The movement of the intestinal
contents along the tract is produced by peristaltic waves, which are contractions of the circular
muscle of the intestinal wall. The contractions are involuntary and are under overall autonomic
nervous control. Digestion begins when feed enters the mouth. The feed is then carried through a
tube called the esophagus to the stomach. When leaving the stomach, the feed moves into the first
section of the small intestine, which is called the duodenum. After traveling through the rest of the
small intestine, what remains of the feed is first emptied into the part of the large intestine named
the cecum and then into the colon. Finally, the waste products are passed into the lower end of the
large intestine, which is referred to as the rectum, and out of the body through the anus. While they
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are not a part of the digestive system, the pancreas, gall bladder, and liver also play a role in
digestion.
The glandular stomach leads to the gizzard which has no counterpart in the pig. This is a
modification of gut of poultry, made up of very strong muscles which are in constant motion
thereby facilitating physical breakdown of feeds. Poultry has another assisting mechanism for
physical degradation. These are small stones in the gizzard called grit, which facilitate physical
degradation of feed by about 10%. This structure or grit could be assumed as substitute of teeth
found in other farm animals. After feed materials get mixed with gastric juice in the proventriculus
the feed goes to the gizzard and chemical degradation is limited in the proventriculus because of
hard nature of the feed. In the gizzard there will be physical degradation which increase the surface
areas of the feed to be attacked by enzymes of proventriculus, but gizzard not produce enzymes.
Therefore, proventriculus & gizzard are equivalent in function to the mammalian stomach. From
the gizzard the feed goes to small intestine which is similar to other farm animals. In fowl two bile
ducts and three pancreatic ducts pour to small intestine. From small intestine feed goes to large
intestine which you find two large blind sacs (ear like structure) called caeca at the junction of
small intestine and large intestine. The caeca functions mainly as absorption organs, but not
essential to the fowl as surgical removal causes no harmful effects. It does not play significant role
in fermentation to poultry. The whole structure of large intestine is much shorter in poultry and
found very short colon in fowl whose function is to transport digesta to cloaca. The large intestine
terminates in the cloaca, a special structure not equivalent to the anus since functions as an orifice
where digestive, urinary and reproductive system products are removed under this common
opening.
Absorption of digested nutrients
The main organ for the absorption of dietary nutrients by the monogastric mammal is the small
intestine. This part of the tract is specially adapted for absorption because its inner surface area is
increased by folding and the presence of villi. Although the duodenum has villi, this is primarily a
mixing and neutralizing site, and the jejunum is the major absorptive site.
Digestion in ruminants
In contrast to an animal with a monogastric digestive system, a ruminant has four stomach
compartments and can utilize some feeds more efficiently than a monogastric animal. Ruminants
are important to the animal industry because they can use hay and pasture productively.
In the GIT of the ruminant, ingested food is exposed to very extensive pregastric fermentation.
Most of the ingesta is fermented by microbes before it is exposed to typical gastric and intestinal
digestive chemicals and enzymes; thus, this is quite a different system than for typical monogastric
animals. The reticulo-rumen provides a very favorable environment for microbial activity and
survival. It is moist and warm and there is an irregular introduction of new digesta and a more or
less continual removal of fermented digesta and end produced of digestion.
They are much larger than bacteria and numbers are less, but they represent about the same amount
of microbial protoplasm as from the bacteria. In addition to bacteria, protozoa, fungi and yeast are
also found in the rumen. The fate of rumen micro-organisms is that they pass into
The abomasum and intestine and are then digested by the host animal. Fibrous feeds are digested
more efficiently in the rumen than in the large intestine or cecum. Cellulose and hemi-cellulose
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can be digested by microbes. Bacteria can utilize simple forms of nitrogen such as urea, to
synthesize their cellular proteins.
In the fermentation process as much as 8-10% of the energy consumed is converted to methane
(CH4), as gas which is wasted and animal cannot utilize. The feed conversion efficiency is low in
ruminants than monogastric animals. The feed conversion ratio (FCR) in ruminants is twice or
more that of monogastric species and the FCR is defined as the units of feed consumed per unit of
product produced.
In the young ruminants the reticulum, rumen and omasum are relatively under developed at birth
because the suckling animal depends on abomasum and intestine for digestive functions. As soon
as the animal starts to consume solid food, the other compartments develop rapidly and they attain
relative mature proportions by about 8 weeks in lambs and kids, 3-4 months in deer and 6-9 months
in domestic bovines. An anatomical peculiarity of ruminant species is that they have a structure
called the esophageal or reticular groove. This structure begins at the lower end of the esophagus
into the omasum.
The groove does not appear to remain functional in older animals unless they continue to suckle
liquid diets. In the ruminant stomach there is a well-developed pattern of rhythmic contractions of
the various stomach compartments which act to circulate ingesta into and throughout the rumen,
into and through the omasum and on the abomasum.
Fibrous diets result in more rumination time. Eructation (belching of gas): Microbial fermentation
in the rumen results in the production of large amounts of gases (CO2 and CH4) which must be
eliminated.
The digestive processes can be classified as mechanical, biochemical and microbial. Much of
the mechanical breakdown takes place in the mouth but all the other sections of the gut are very
muscular and help to move the feed along by peristaltic action and also mix and churn the ingesta.
The biochemical digestion is carried out largely with the help of enzymes Secreted into the gut at
various stages. The microbial digestion or fermentation process takes place mainly in the rumen
but also to a lesser extent in the hind gut. The ruminant’s stomach consists of four compartments;
rumen (paunch), reticulum (honeycomb), omasum and abomasum (true stomach). In young calf
or unweaned calf the abomasum acts as true stomach.
Weaning is change from liquid to solid feeding. The reticulo-rumen forms a large fermentation
organ which contains billions of microbes, of which the two main types are bacteria and protozoa.
The microbial population ferments the organic matter contained in the solid feed, converting it into
very simple chemical substances, such as ammonia and volatile fatty acids.
The two most important nutritional functions of the reticulo-rumen are the modification of the
energy and protein fractions of the feed into very simple chemicals entities.
Metabolism of nutrients
Metabolism is a general term given to the sequence of chemical processes that take placed in the
living organism. These reactions continue as far as the living body exists. These processes can be
categorized into three
1. Anabolism; describes the metabolic processes in which complex compounds are synthesized
from simpler substances.
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2. Catabolism; describes metabolic processes that involve the degradation or breaking down of
complex compounds to simpler molecules.
3. Waste product transformation; as a result of the above two metabolic processes, waste
products arise which has to be chemically transformed and ultimately excreted
Nutritional disorders and Anti-nutritional factors
Nutritional disorders which are due to nutritional deficiencies, such as milk fewer, lactation tetany,
ketosis, pregnancy toxemia of ewes, bloat, ingestion etc. These diseases are not due to the infection
or toxic agent but due to the disturbance in the normal metabolism in the animals.
1. Indigestion or acidosis: Sudden change in the dietary of animals on high grain feeding of wheat,
corn etc. leads to acute and fatal indigestion in ruminants. Feeding ruminants on large quantities
of grains contains soluble sugars leads to massive production of lactic acid in the rumen as results
of rumen fermentation.
The animals should be introduced on grains gradually to high grain and low roughage diets rather
than a sudden change.
2. Bloat (Tympanitis): In the bloat the rumen is dilated with gas (CO2 and CH4). Bloat is
characterized by the distension of the rumen by a foaming mass of contents which the animals
cannot eliminate by belching. Bloat is generally observed in cattle while grazing the pastures in
monsoon and eating clovers like alfalfa.
To prevent the bloat- feed 1-2 kg of wheat straw with green fodders.
3. Milk Fever (Hypocalcaemia): There are many factors for milk fever in which the calcium level
in the blood falls down. In high producing cow and buffalo immediately after parturition, the
calcium level goes down so much that animal becomes unconscious and dies if treatment is not
given. Not only Ca but sometimes P level also goes down. Calcium gluconate injection improves
condition.
4. Hypomagnesaemia: This condition is a result of Mg deficiency in the diet and leads to muscle
tremors/tetany. It is more common in grazing cows and is often known as grass tetany. Intravenous
or subcutaneous injections of Mg chloride or Mg sulfate are generally given to alleviate the
condition.
5. Ketosis: This is a condition in which aceto-acetic acid, beta-hydroxy butyric acid and acetone
accumulate in the blood due to impaired metabolism. In cattle it is observed in early lactation and
in sheep in the last month of pregnancy especially when they are carrying twins and triplets.
6. Post Parturient Haemoglobinuria: P deficiency haemoglobinuria has been reported in mature
dairy animals. P supplements reduce the incidence of this disease.
7. Urea/Ammonia Toxicity: Increased intake of urea fed as feed supplement in the diet of
ruminants may cause urea toxicity. This is due to the high ammonia circulation in the blood which
the liver cannot detoxify, vinegar; dilute acetic acid (5% solution), ice-cold water be offered, which
may be helpful in reducing the toxicity.
Anti-nutritional Factors
14
Certain animal feedstuffs and forages contain substances which can significantly reduce their
nutritive value. They are called as toxic factors, as they produce deleterious effects when consumed
by animals. The term toxic factors are misleading because these substances are lethal beyond a
certain level of intake. In most animals they produce lesser effects e. g. reduced growth, poor FCR,
hormonal changes and organ damage. Better to call them
ANF’s (Anti-nutritive factors/substances). They are defined as “those generated in natural
feedstuffs by normal metabolism from which the material originates by different metabolism,
decomposition or inactivation of nutrients, digestive disorders or metabolic utilization of feed,
exert effects on optimum nutrition”. Artificial antagonists are different than ANF’s, for example
when preservatives or other chemical additives, which can inactivate or destroy certain nutrients;
toxic compounds which may result from different manufacturing processes: like pesticides,
herbicides and mycotoxins.
These are classified on the basis of type of nutrients they affect, either directly or indirectly, and
the biological response produced in the animals.
1. Substances depressing digestion or metabolic utilization of proteins:
1 Protease inhibitors
2. Lectins
3. Saponins
4. Polyphenolic compounds
Protease inhibitors are destroyed by heat treatment.
The different methods of heat treatments that can be employed are:
1) Moist heating (cooking and autoclaving),
2) Dry heating,
3) Extruding and
4) Infra-red cooking or micronization.
The important factors controlling trypsin inhibitors destruction are temperature, duration of heat,
particle size and moisture level. Overheating leads to damage of amino acids and vitamins. Quality
control can be maintained by determining the inhibitors by different methods like
a) Urease assay
b) Trypsin inhibitor
c) Cresol red absorption,
d) Protein dispersibility index (PDI) and
e) nitrogen solubility index (NSI).
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2. FORAGE AND PASTURE PRODUCTION AND MANAGEMENT
Learning Outcomes:
Upon successful completion of this course, students should be able to:
 Identify the major livestock feed resources;
 Identify some of the most important grass, legume and forage tree species that yield maximum
production under tropical conditions;
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 Clarify about factors affecting pasture improvement and methods of improving natural pasture;
 Know appropriate agronomic practices that will help to establish pasture crops and increase
their productivity;
 Know important pasture management practices that yield maximum forage production; and
thereby support optimum animal production.
INTRODUCTION
1.1. General Description of Forage Crops and their Importance
Forage: Forage is a plant material (primarily plant leaves and stems) consumed by grazing
livestock or Forages, defined as the edible parts of plants other than separated grain that provide
feed for grazing animals or can be harvested for feeding. Play an important role in the beef cattle
industry, wildlife habitat, and soil ecosystem service.
The common forage crops are
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 Grasses
 Silage
 Herbaceous legume
 Crop residue
 Tree legumes
Classification of forage crops
 Classification of forage crops based on life forms
Annuals: These are generated from seed and resown each year. The plant usually dies after seeds
are produced. Examples of annual forages are Vigna unguiculata(cowpea) and Vicia spp
(vetch).
Biennials: The parent plants live for two seasons and careful management is needed to ensure
seed production, e.g. Lolium multiflorum.
Short-lived perennials: These can regenerate vegetatively and do not usually survive longer
than three to five years. e.g. Sesbania sesban and and Medicago sativa
Perennials: These may survive from 5-20 years through maintenance of the original plant.
Examples are Brachiara decumbens (signal grass), legumes such as the stylos and most of the
fodder tree species.
 Classification of forage crops based on growth habit
 erect,
 twining or
 sprawling,
 creeping habit
 Ecological classification /grouping of forage crops
Altitude: Each forage species have its own range of altitude at which best performance or
adaptability could achieve. For e.g. high land, mid altitude and low land
Soil type: consider the soil type, its structure and pH condition
Temperature: warm temperature with enough amount of moisture could favor for most species.
Rainfall: Moisture amount of the area could play significant role for best adaptation. Excess and
amount of precipitation could affect the adaptation. Failure due to excess moisture could occur
on the highlands when the soil type is heavy (vertisol) this is mainly due to poor drainage
condition of the soil.
Importance of forage crops
 Increase the supply of forage for
ruminant livestock;
 Restore degraded land, salty areas
 Improve farm profitability
 increase draught power for cropping;
and
 The key to sustainable farming
 Benefits for the environment
 Increase fuelwood and other tree
products.
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CH 2. FEED RESOURCES AND FEED PRODUCTION SYSTEM IN ETHIOPIA
2.1. Main Feed Resources in Ethiopia
The main feed resources for livestock in Ethiopia are
 Natural pasture
 Agro-industrial by-products and
 crop residue
 Other by-products like food and
vegetable refusal,
 Improved pasture and forage
Natural pasture: comprises the largest share of livestock feed, the availability and quality of
native pasture vary with altitude, rainfall, soil type, and cropping intensity.
Cultivated pastures: Grasses, herbaceous legumes, tree legumes
Conserved forages: hay and silage
Crop residue: Crop residues were the second major feed resource next to natural pasture. It is the
leftover portion of the crop after the main crop is harvested for human consumption.
Cereal crop residues/straws; Teff, wheat, barley, maize, sorghum etc.
Pulses crop residues/haulms; haricot beans, field peas, chickpeas, lentils, groundnut.
 Crop residues are generally characterized by; High fiber content, and low content of soluble
carbohydrates and protein. Cereal straws 3-5% CP, low content of essential minerals and
vitamins, low digestibility (30-45%), low intake promoting low level of performance
 The nutritive value of crop residues can be affected by;
 Stage of maturity at harvest
 Processing
methods
(physical,
 Harvesting and handling losses
chemical, biological)
 Presence of toxic materials
 Plant morphological component
 Agro-climatic conditions
Agro-industrial by-products: Agro-industrial by-products have special value in feeding
livestock mainly in urban and peri-urban livestock production systems, as well as in situations
where the productive potential of the animals is relatively high and require a high nutrient supply.
Are rich in energy and/or protein contents or both. They have low fiber content, high digestibility,
and energy values compared with the other class of feeds.
 The major agro-industrial by-products commonly used are obtained from flour milling
industries (wheat bran, wheat short, wheat middling, and rice bran),
 Edible oil extracting plants (noug cake, cottonseed cake, peanut cake, linseed cake, sesame
cake, sunflower cake, etc.),
 Breweries and sugar factories (Molasses).
Other by-products like food and vegetable refusal:
 Different types of organic wastes play a key role in urban agriculture.
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 Organic wastes from hotels, cafés, and markets are fed to animals, which roam freely,
consuming waste around municipal bins and in the marketplaces.
2.3. Limitation of pasture and forage resources
Feed Quality and Quantity: Natural grazing is the major source of livestock feed, and in the
lowlands, livestock production is almost totally dependent on it however, grazing lands do not
fulfill the nutritional requirements of animals.
Ecological Deterioration: Gradual encroachment of cultivation into grazing lands is common in
both highlands and mid-altitude areas so many meadows in the flood plains have been converted
into croplands.
Overgrazing: Grazing and browsing animals overstock natural pastures; areas near water points
are generally the most affected.
Drought: One of the most unfortunate characteristics of Ethiopia’s climate is the great variability
of rainfall from year to year. Drought is particularly common in the pastoral area where rainfall is
erratic and unreliable.
Weed and Bush Encroachment: As a result of overgrazing many natural grazing lands are
invaded by unpalatable weeds and woody plants.
Soil Fertility: The annual food and livestock feed shortage of the country is attributed directly to
soil erosion and nutrient export.
Lack of Seed and Planting Materials: The absence of quantity and quality seed and seedling
production limits the vast expansion of improved pasture and forage development (especially
around dairy farming and fattening areas).
2.4. Opportunities for improvement of forage resources
Pasture and Forage Genetic Resource: Pasture Species: Since Ethiopia is known to be the
Centre of origin and diversity for a number of domesticated crops, it is also known to be the center
of diversity for pasture and forage species.
Biodiversity conservation. Conservation and use of grass germplasm have made a significant
contribution to the economic development of Ethiopia through the national pasture and forage
research programme.
Pasture Rehabilitation: Because of Ethiopia's diverse climate, there are a number of valuable
wild grasses and legumes and browse plants. The highland is rich in pasture species, especially
legumes. There is a wide diversity of annual and perennial Trifolium species and annual Medicago
in the highlands, particularly above 2,000 meters.
Sown Pastures and Forages: Climate and land availability provide a good opportunity for forage
production. In Ethiopia most improved tropical species can be grown in the lowlands (1,500-2,000
meters) and temperate species grow from above 2,100 meters up to 3,000 meters.
CH 3. BOTANY OF LEGUMES AND GRASSES
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3.1. Grouping of grass pasture
Taxonomy and evolution
 The grass family, Gramineae (Poaceae) consists of five subfamilies.
 Bambusoideae
 Chloridoideae
 Arundinoideae
 Pooideae
 Panicoideae
Bambusoideae and Arundinoideae are less developed compared with the other three subfamilies.
The closest living relatives of grasses are the rainforest monocot plant families such as Palmae and
Flagellariaceae.
The Panicoideae and Chloridoideae: are related to Arundinoideae and contain almost all the
successful tropical savanna pasture species.
 Grasses in the world are grouped into 620 genera with nearly 10,000 species.
 They have a wider range of adaptation than any other family of flowering plants grown in
different agro ecological zones.
 Based on the embryo structure within the seed, grasses are classified as monocotyledons while
legumes as dicotyledons.
 Grasses in the world are grouped into 620 genera with nearly 10,000 species.
 They have a wider range of adaptation than any other family of flowering plants grown in
different agro ecological zones.
 Based on the embryo structure within the seed, grasses are classified as monocotyledons while
legumes as dicotyledons.
 Leaves are borne on the stem, one at each node, but are projected alternately in two rows on
opposite sides of the stem.
 The leaf consists of a sheath, blade and ligules.
 The unit of a grass inflorescence is the Spikelets occur in groups or clusters, collectively termed
the inflorescence.
Common types of grass forages
Nappier Grass: Fast-growing, deeply rooted, perennial grass growing up to 4 meters tall that can
spread by underground stems. Important fodder crop in the cut-and-carry system of dairy. It is
high yielding; good palatability; good nutrient content when young (dark green, less than 1 meter
tall).
Rhodes Grass (Chloris gayana): A vigorous, perennial grass, with a strong root system giving
good drought tolerance. It spreads quickly forming the good ground cover and grows to 1.5 meters
tall useful in the cut-and-carry system and for open grazing does well in low rainfall areas and is
drought tolerant stands heavy grazing; very palatable; good for hay making.
21
Buffel Grass (Cenchrus cilaris): Buffel Grass is extremely drought tolerant. Is a very robust grass
for areas below 2000 m with more than 250 mm annual rainfall. It is adapted to heavy cutting or
grazing but is less palatable than many other types of grass. It establishes well from seed. Is well
suited to the improvement of stock exclusion areas and the rehabilitation of degraded areas.
Guinea Grass/Panic (Panicum maximum): Panic is an erect grass, useful for strip planting or
mixed pastures suitable in areas below 2400 m altitude and >500 mm annual rainfall. It grows on
most soils but requires high fertility for good productivity. Panic produces good quality forage and
is well adapted to cutting or grazing.
Setaria (Setaria sphacelata): Setaria is a widely adaptable species for areas below 2400 m
altitude with more than 700 mm annual rainfall. It grows on a wide range of soils and tolerates
water logging. Setaria is ideal for contour forage strips where it can be established by direct seeding
or from splits.
Phalaris (Phalaris aquatica): Most important grass for forage and soil conservation
Performs well between 1800 and 3000 m altitude. Are frost and drought-tolerant and is produced
with more than 400 mm annual rainfall. Requires fertile soils for strong growth but will survive
on poor soils, although its conservation value is diminished on such soils. Phalaris establishes
slowly but once developed is well adapted to heavy grazing or cutting and it is suitable for contour
forage strips and backyard forage and mixed pasture strategies.
3.2. Grouping of legume pasture
Taxonomy and evolution
Leguminosae (17,000 spp) is the 3rd largest plant family
It has three subfamilies- Caesalpinioideae
Mimosoideae
2900 species
2900 specie
Papilionoideae
11000 species
Caesalpinioideae: contains 174 genera with about 672 species
Three genera contain herbaceous species the rest are woody.
21 Genera with browse potential are endemic to Africa
Mimosoideae: contains 56 genera and 2832 spp
Genera with about 6oo species have forage potential
toxic compounds are common in the subfamily
Papilionideae: There are 456 genera and 11271 spp in the world
Contain 345 genera with about 7000 species in the tropics
Most of these are herbaceous
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 There are nearly 600 genera and 12,200 species of legumes worldwide.
 Legumes have a narrower range of adaptation and usually require a higher management level
than grasses.
 Leguminous plants are dicotyledons and may be annuals, biennials or perennials.
 Most legume plants grow symbiotically with rhizobium bacteria that form nodules on the roots.
These bacteria use plant carbohydrates to reduce atmospheric nitrogen making it available to
the plant.
 Legumes are valuable components in forage mixtures, as well as in crop rotations, to decrease
dependence on nitrogen fertilizers.
 Leaf blades connect to the stem by petioles.
 Stems of legumes vary greatly between species in length, size, amount of branching and
woodiness.
Siratro (Macroptilium atropurpureum): Siratro is a perennial, sprawling/ climbing forage
legume. An important role in under-sowing and stock exclusion areas. Its primary use is for forage,
but also used for erosion control and nitrogen fixation
Axillaris (Macrotyloma axillare): Axillaris is a perennial, sprawling/ climbing forage legume
highly suited to under-sowing, intercropping, and improving stock exclusion areas. It grows best
in complement with Siratro and Greenleaf Desmodium.
Desmodium species: Desmodium is a climbing perennial legume with small leaves and deep roots
which, in favorable conditions, forms a very dense ground cover. It is popular in cut-and-carry
systems. For areas with two rainy seasons, sow seeds during the short rains but plant cuttings
during the long rains. The seeds can be sown either by drilling or by broadcasting.
Silverleaf (Desmodium uncinatum): Silverleaf is a perennial, sprawling forage legume suited
to under-sowing, intercropping, and improving stock exclusion areas. It has green and white
leaves which are light green underneath.
Greenleaf (Desmodium intortum): Greenleaf is less tolerant of cool weather and light frosts. It
is a perennial, sprawling forage legume suited to under-sowing, intercropping and improving stock
exclusion areas. Its use is in forage production and for nitrogen fixation and erosion control
Lablab (Lablabpurpureus): It is a vigorous annual or short lived perennial legume with very
vigorous seedlings, which is best as a dual-purpose species.
Cow Pea (Vigna unguiculata): Annual dual-purpose legume suited to a wide range of
environments. Cow Pea grows in lowlands up to 2500 m and is drought tolerant – maturing with
anything more than 300 mm annual rainfall. Grows on a wide range of well-drained soils and will
tolerate gentle cutting or grazing during the growing season.
Vetch (Viciadasycarpa): range of adaptation and high level of farmer acceptability. Grows well
between 1500 and 3000 m altitude and is suited to a wide range of rainfall – typically anything
23
above 400 mm per annum. Grows on wide range of soils but requires good drainage for optimum
productivity.
Alfalfa (Medica gosativa): Alfalfa is a deep-rooted, perennial herbaceous legume that produces
a lot of stems and leaves and, upon maturity, small purple flowers. It is established from seed. It
is used as a supplementary forage for dairy cattle and it is high in nutrients and highly palatable.
Fodder tree/browse legumes
Tree legumes are extremely important elements in improved forage production programs because
of their productivity and multi-purpose uses.
Apart from large quantities of quality forage, browse legumes have deep rooting systems to
increase their productivity during the dry season
Leucaena species: Leucaena is a browse legume of great importance in Ethiopia
•
Provide highly palatable, nutritious forage
•
Planted in cut-and-carry plots, grazed plots, along boundaries or even along contours for
soil erosion control.
Sesbania (Sesbania sesban):
•
Sesbania is an adaptable browse legume which will live for up to 7 years
•
It is highly palatable and also uses for shelter, and nitrogen fixation for companion crops
•
Climate: Sesbania produces best below 2000 m altitude,
•
Very frost sensitive, and not very drought tolerant – requiring more than 600 mm annual
rainfall for survival.
Pigeon Pea (Cajanus cajan)
•
Short-lived dual purpose shrub legume providing forage, grain for human consumption, and
low quality fuelwood
•
Climate: Pigeon Pea adapts well in altitudes below 2400 masl
•
Requires more than 350 mm annual rainfall for good production.
Tree Lucerne/Tagasaste (Chamaecytisus palmensis)
•
A temperate, multipurpose browse legume of highland areas of Ethiopia
•
Highly productive for altitudes above 2000 m altitude
•
Climate: Tree Lucerne is drought tolerant once established but requires more than 400 mm
rainfall for maximum productivity
Soils: Tree lucerne tolerates mild frosts but will not tolerate water logging at all. Most suited to
well-drained fertile soil
CH 4. CLIMATIC FACTORS AND PASTURE GROWTH
24
4.1. Climatic Factors
1. Light- Determines plant growth through direct input of energy into the photosynthesis
system, into the transpiration process and as a determinant of leaf temperature. The amount
of radiation received on the earth surface depends on the degree of atmospheric filtration.
The atmospheric filtration at the earth surface depends on (determined by):
a. Latitude and altitude- The higher the latitude, the lower total solar energy.
b. Cloudiness & atmospheric turbidity caused by water vapour, dust, smoke, and
other aerosols- The importance of solar radiation in pasture production lies in the
fact that the rate of photosynthesis is related to the amount of radiation energy
received. Thus, the higher the rate of photosynthesis the higher accumulation of
dry matter (herbage).
2. Temperature- The temperature of the plant is basically determined by the radiation
regime and the ambient air temperature modified by the aspect in which it is growing,
etc.

Effects of extreme high temperature (lethal maximum)
Inhibition of photosynthesis, increased rate of photorespiration and/or dark respiration,
irreversible biochemical damage and denaturation of enzymes leading to death of the plant.
Effects of extreme low temperature (lethal minimum)
Decline of the rate of reaction in enzyme systems involved in photosynthesis, changes in
chloroplast structure, stomatal closure & hence no exchange of gases.
For many species the lethal temperature is achieved at -2 to 0 0C.
Effects of temperature on growth of tropical pasture species
Tropical grasses- Increasing temp cause an increasing rate of tiller development increase in leaf
area & leaf length in tropical grasses.
Tropical legumes- For the tropical legumes, the optimum temp is around 31 0C, with minimums
similar to the grasses between 5 and 8 0C but with lower maximums of 50 0C.
Temperate grasses & legumes - Low temperature favors tiller production, particularly where
low night temperatures are associated with high day temperatures. Optimum 10-25 0C and the
max. 40-45 0 C, and the min less than 5 0C.
3. Moisture (rainfall) - Moisture stress in plants has the following results: a decline in
metabolic activity, reduced rate of photosynthesis, loss of turgor and progressive stomatal
closure, reduced rate of leaf area development, death of existing tissue.
4.2. Soil factors
1. Physical factors: Factors such as soil depth, texture, structure, and also the slope at a particular
site are basic soil features affecting many aspects of fertility.
Soil depth: Adequate depth is essential to give roothold for plant, to provide an adequate supply
of essential nutrients, and to provide a store of water. Shallow sites often occur in upper steepy
sloping positions so that erosion is a further hazard.
25
Soil texture: Refers to the particle size (coarse sand, fine sand, silt & clay).
Soil structure: The ability of the soil to produce and maintain aggregates of a suitable size (0.5 to
a few millimeters), especially in the soil surface, is an important soil characteristic affecting
particularly the physical properties of the soil.
2. Chemical factors: Adequate nutrient supply: Some 15 elements (excluding carbon, hydrogen,
and oxygen) have been shown to be essential to the growth of plants, i.e. N, P, K, S, Ca, Mg,
Fe, Mn, Zn, Cu, Mb, Cl, B, Co, Na, and additional two for animals (Selenium, Si and iodine,
I. Micronutrients are important in plant biochemistry as constituents of enzymes and hormone
systems, which control processes such as respiration, energy exchange, and synthesis of
chlorophyll, carbohydrates, and proteins.
CH 5. FORAGE CROPS INTRODUCTION AND EVALUATION
5.1. Desirable characteristics of forage crops
 Good forage should grow well and survive with a minimum of care. Even though it is
desirable to treat pastures and fields of forage crops as carefully as possible, nevertheless,
a good forage crop should resist neglect and abuse.
 Good forage should also resist the dry season of the year, continuing to grow or
maintaining foliage and nutritive value and, above all, living through the dry season so that
growth is resumed again with rains.
 Or, in the case of forage cut as hay, it should be uniform, timely, and manageable, have
good keeping qualities, and be nutritious.
 Naturally, good forage should be palatable to the animals for which it is grown. This
palatability should extend throughout the year.
 When the forage is used through cutting or pasturing, it should regenerate rapidly.
 The overall yield should be high, and this depends in part on previously mentioned factors.
 Finally, nutritional value should be high.
 Height of forage is an important characteristic. Tall forages are easy to cut but difficult to
graze.
5.2. Selection of forage crops
Principles for Selection and Testing
 The key principles for selecting improved forage species and their cultivars focus on their
ability to persist under normal management conditions and produce large quantities of high
quality forage. This means that the species should tolerate grazing, and be able to flower and
set seed under normal grazing conditions.
 Suitable species will be drought tolerant in order to maximize production in an environment
characterized by a dry season. Species with different plant forms and modes of reproduction
should also be selected for to maximize the opportunities for integrating improved forages into
different farming systems and ecological niches.
 For example, tall growing species such as Seca stylo are suitable for cut and carry systems
associated with strategies for oversowing natural grasslands. Similarly, sprawling vigorous
legumes such as Siratro and Greenleaf desmodium are suitable for undersowing and
intercropping. Seed bearing species (such as stylo and tree lucerne) should be mixed with
vegetatively reproducing species (such as Rhodes grass or hybrid Phalaris) to optimise
ecological stability of introduced forage mixes.
26
 When assessing growth rates and productivity, it is important to understand the life cycle and
growth habits of each species and cultivar. Stylos, for example, are slow to become established
but after two or three years are highly productive.
 Because the ultimate objective of forage production is to increase the quality of livestock
forage as well as the quantity, qualitative aspects of forages should also be considered during
selection and assessment of new forages.
 Palatability, digestibility and nutrient balance should be measured. The occurrence of toxic
substances - for example indospicine in lndigoferci spicata or mimosine in Leucaena - should
also be considered.
 The site itself will determine in part the forage to be grown. The decision will have to be made
whether the area will be grazed or the forage will be cut and removed. Adaptability of the
forage to the site is the most important consideration. This will be determined by elevation,
soil type, rainfall amount and distribution, and temperatures.
CH 6. PASTURE YIELD AND QUALITY
6.1. Forage Quality
6.1.1. What is forage quality?
Forage quality can be defined as the extent to which forage has the potential to produce a desired
animal response. Factors that influence forage quality include the following; Palatability; Will the animals eat the forage? Animals select one forage over another based on
smell, feel, and taste. High-quality forages are generally highly palatable.
Intake; - How much will they eat? Animals must consume adequate quantities of forage to
perform well. Typically, the higher the palatability and forage quality, the higher the intake.
Digestibility; How much of the forage will be digested? Digestibility (the extent to which forage
is absorbed as it passes through an animal’s digestive tract) varies greatly. Immature, leafy plant
tissues may be 80 to 90% digested, while less than 50% of mature, steamy material is digested.
Nutrient content; once digested, will the forage provide an adequate level of nutrients? Living
forage plants usually contain 70 to 90% water. To standardize analyses, forage yield and nutrient
content are usually expressed on a DM (DM) basis
Anti-quality factors; various compounds may be present in forage that can lower animal
performance, cause sickness, or even result in death. Such compounds include tannins, nitrates,
alkaloids, cyanoglycosides, estrogens, and mycotoxins.
Animal performance; is the ultimate test of forage quality, especially when forages are fed alone
and free choice. Forage quality encompasses “nutritive value” (the potential for supplying
nutrients, i.e., digestibility and nutrient content), how much animals will consume, and any antiquality factors present.
6.1.2. Agronomic factors affecting forage quality
 The major agronomic factors that affect forage quality are cutting schedules (plant maturity at
harvest), weed and pest management, harvest effects, variety and seasonal or short-term
27
weather patterns. Time of day of harvest, fertilizers, variety and irrigation can also impact
quality.
Plant Maturity at Harvest: Maturity stage at harvest is the most important factor determining
forage quality of a given species. Forage quality declines with advancing maturity. For example,
cool season grasses often have DMD (DM) digestibility above 80% during the first 2 to 3 weeks
after growth initiation in spring. Thereafter, digestibility declines by 1⁄3 to 1⁄2 percentage units per
day until it reaches a level below 50%. Maturity at harvest also influences forage consumption by
animals.
Cool-season vs warm-season grasses; Forage grasses are divided into two broad categories: cool
season (adapted to temperate regions) and warm season (best adapted to tropical or subtropical
environments). Cool-season grasses include orchard grass, Kentucky bluegrass, perennial and
annual ryegrass, and tall fescue. Bermuda grass, bahia grass, dallis grass, and corn are examples
of warm-season grasses. Cool-season species are generally higher in quality than warm-season
grasses.The digestibility of cool season grass species averages about 9% higher than warm-season
grasses.
Leaf-to-stem ratio; Reduced leaf-to-stem ratio is a major cause of the decline in forage quality
with maturity, and also the loss in quality that occurs under adverse hay curing conditions. Leaves
are higher in quality than stems, and the proportion of leaves in forage declines as the plant matures
Fertilization; Fertilization of grasses with nitrogen (N) often substantially increases yield and also
generally increases CP levels in the forage
Daily fluctuations in forage quality: Recent studies in low rainfall climates have shown higher
forage quality when alfalfa is harvested in the late afternoon rather than in the morning. It appears
that the advantage of afternoon harvest is greatest on cool, sunny days and when the forage is
highly conditioned to increase drying rates and minimize respiration in the windrow. However,
afternoon harvests may not be advisable in high rainfall areas where every hour of good drying
time is needed in curing hay.
Variety effects; There are many examples of plant breeding improving forage quality. The variety
‘Coastcross-1’ Bermuda grass is about 12% higher in digestibility than ‘Coastal’ Bermuda grass,
supporting 30% higher average daily gains by beef steers. In species such as timothy that have a
wide range of maturity dates, later maturing varieties tend to be slightly lower in digestibility
because early types make more of their growth under lower temperatures. Some silage corn
varieties have higher grain content and/or stover digestibility than others.
Harvesting effects; Leaf shatter, plant respiration, and leaching by rainfall during field drying of
hay can significantly reduce forage quality, particularly with legumes. Moderate rain damage
reduced alfalfa CP levels slightly and digestibility dramatically, but NDF and ADF levels
increased sharply.
Rainfall during curing damages legume leaves most. For alfalfa hay exposed to both drying and
leaching losses, more than 60% of the total losses of dry matter, CP, ash, and digestible DM were
associated with the leaves. Rain during field drying has less impact on the forage quality of grasses
than legumes.
Weeds and Species Mixtures: Although weeds can theoretically have neutral, positive, or negative
effects on forage quality, the overwhelming effect is negative. Most weeds, especially grassy
weeds, increase the NDF concentration (fiber) and lower intake and reduce NDFD, decrease
protein and digestibility.
28
CH 7. PASTURE ESTABLISHMENT AND SEED PRODUCTION
Types of Pasture
Natural pasture: Natural (native) pastureland is determined by, among other things, vegetation
remaining in the land, edaphic and climatic factors that determine plant growth, and the current
land system of the land.
Cultivated pasture: The establishment of a permanent cultivated pasture plots requires the introduction of
planting materials from other geographical areas (within or outside a country).
Approaches of Establishment
Common ways of establishing forage plants are: Direct seeding, Seedlings, Cuttings and Splits
Plant species, planting material availability and environmental conditions all determine the choice
for these methods of establishment.
Generally, the following guide can be used: Tree legumes: seedlings, cuttings, and direct seeding,
Herbaceous legumes: Direct seeding, Grasses: Direct seeding, cuttings, and splits
 Before sowing it is useful to determine the viability of the seeds (if not commercial and
guaranteed) by carrying out a germination test. Some seeds may also require seed treatment
and inoculation (only legume seeds).
Seed quality: is an important parameter to look into before sowing of seeds. This seed quality is
defined first by the proportion of seeds which will germinate and secondly by the freedom of the
seed from contamination by seeds of different genetic constitution, by inert material or by pests
and diseases.
Viability: refers to the capacity of the seeds to germinate after sowing. When the seed (comprising
an embryo and endosperm energy reserves, surrounded by a seed coat or testa and other outer
coverings) is placed in a moist environment falling within a specific temperature range, it absorbs
moisture and various biochemical changes begin
Seed treatment: Different types of seed require different treatments in order for optimal
germination. The main purpose is to break their dormancy, improve seed flow characteristics and
allow rhizobium inoculation and protective chemicals to surround the seed.
Inoculation of seeds: In addition to seed treatment inoculation with specific rhizobial bacteria
may be required. These bacteria fix nitrogen and make it available to the plant. In introduced
species of legumes this must be done before sowing for efficient nitrogen fixation.
Use of fungicides and pesticides: legume seedlings are highly susceptible to fungal diseases and
may be killed shortly after emergence (a condition known as ‘damping off’). Grasses also suffer
from seedling diseases and the seeds can be damaged by insects. Thus seed treatments with
fungicides and pesticides can help the initial stages of plant growth.
Establishment from seedling: Establishment from Seedling is the second option involving the
growing of seedlings in nursery either potted in polythene bags or bare rooted. Either type of
seedling may also be planted with a bare stem (to reduce loss of moisture during transport and
immediately after planting through transpiration
Establishment from cuttings, splits and runners
The third option of establishing forages is from cuttings, splits and runners. Tree legumes and
some grasses can be propagated from cuttings at a cheaper price than seed production. Such
cuttings should have about the thickness of a thumb and 30 - 50 cm long and cut at 450angle.
Tussock (bunch) forming grasses such as elephant grass may be propagated using splits. This
29
involves cutting the top parts and digging up the root stocks and splitting it into sections each with
at least one shoot. Some grasses such as Rhodes grass can be propagated by mature stolons called
runners. Sections with at least 3 nodes are cut off, planted, and covered with soil.
Pasture establishment on fully cultivated seed bed: The following general practices should be
considered when establishing a pasture seed crop:
1. Site Selection: It is essential to choose a site which is favorable for seed production.
Environmental requirements include: I) frost free during flowering and seed ripening ii) sufficient
rainfall iii) well drained soil situation factors required are: i) Sites should be accessable and
clustered for ease of supervision by the Development Agent. ii) Labour must be available for
harvesting.
2. Land clearing: Newly-cleared land is often used for seed crops to ensure less competition from
weeds and other pasture plants (and therefore less contamination of the crop). This is particularly
important with some of the less competitive legumes where less fertile land is used. This can also
be the case with more competitive grasses where no suitable pre-emergence herbicide can be
recommended.
3. Seed-bed preparation: For seed crops, thorough land preparation is essential to provide a clean,
firm fine seed-bed. Land leveling is advantageous for irrigated systems or mechanized harvesting.
Rough, weedy underdeveloped/under-prepared seed-beds may cause poor establishment giving
poor plant populations which allow uneven tiller and seed maturation.
4. Reduction of Seed Hardness: Any legume seed which is hard should be softened so that it
germinates rapidly, taking advantage of all the available rain all, Reducing the hard seed content
to below 40% will not only supply sufficient seed for a dense crop but also retain a reserve of seed
in case of early establishment difficulties, for example minor rainfall causing germination followed
by drought which kills seedlings. Pulse (food) legumes have low proportions of hard seed and do
not require seed softening. The herbaceous and tree forage legumes have varying portions of
hardness with highest levels in seca and verano stylo, wynn cassia and leucaena.
5. Ageing of grass seed: Most freshly harvested grass seed is temporarily dormant and will not
germinate. It must be stored for 6 months after harvest before it is ready for sowing.
6. Inoculating legume seed: Legumes obtain their nitrogen from microorganisms called rhizobia
which invade their roots to form nodules. Different legumes require different types of rhizobia.
Some legumes are able to use rhizobia which are already present in the soil, for example, vetch,
stylos, siratro, glycine, axillaris, siratro, lablab, and cowpea. Other legumes need specific rhizobia,
for example, maku lotus, forage peanut, lotononis, leucaena, tree lucerne.
7. Sowing
Time of sowing: Planting time depends largely on the reliability of rainfall and potential evapotranspiration. Early sowings have the best chance of producing a good harvest. Within given areas,
small niches may exist which allow for different timetables to take advantage of rainfall extremes,
irrigation and weed control patterns.
Asexual Propagation
30
Seedlings: May be used as an alternative to sowing seed of tree legumes and for bulking up seed
from small imported samples. The advantages of planting tree legumes as seedlings are that there
is a higher survival rate and that the trees are able to achieve greater size in the year of sowing. As
seedlings are more expensive than direct seeding they are not used for broadscale planting of
herbaceous legumes arid grasses.
Cuttings: May be used for propagating some forage species, mainly tree legumes and grasses.
8. Fertilizer requirements and application: Adequate fertilizer applications are required to
promote plant growth and subsequent seed production. General pasture recommendations are
usually followed for pasture seed crops as well. The fertilizer should be evenly distributed. On less
fertile soils, 50 kg N/ha should be applied to grasses at establishment but this dressing can be
reduced or eliminated when the soils are considered fertile. Mixing fertilizer with seed at time of
sowing can result in an interaction which reduces germination and inoculants effectiveness.
9. Weed control: Weed control measures taken in the seed-bed help ensure successful
establishment. Pre-emergence herbicides may be used but are too expensive for many seed
producers. The selection of planting time and hand weeding (where cheap labour is available) are
alternative methods of weed control.
Choice of vegetative material or seed:
Vegetative material may be in the form of rhizomes, stolons, stem pieces or cuttings (splits). Such
materials are genetically identical to the parent plant. Whether seed is sown by hand or machine
good quality seed must be used. If the resultant crop is to be certified, seed of the appropriate status
or generation must be used.
Establishment problems
Several problems relating to establishment are often faced by farmers involved in seed production.
These problems generally fall into four types. These are:
Physical loss of seed due to predators (eaten or removed)
Loss of seed viability due to environmental stress
Failure of germinated seed to emerge from the soil due to environmental stresses or
mechanical impediments in the soil
Mortality of emerged seedlings due to environmental stresses, plant competition or
pathogen or pest attacks.
Measurement of forage yield/ production: The productivity of a pasture can be directly
measured through cutting experiments but such experiments are of little use if they are not
combined with studies on the effects of the different feeds or pasture quality on animal
productivity. Thus, Pasture measurement involves two biological systems; the plant and the
animal. Aspects of the systems that are needed by the animal producer and the pasture investigator
include the quality and continuous supply of forage; the amount of herbage consumed by the
grazing animal, nutritive value and digestibility of the herbage and animal performance. The
quantity of pasture produced by a pasture or grazing land can be measured by weight, visual
estimates and animal output. Some of the forage measurement are:
1. Biomass production
2. Botanical composition
31
Factors affecting seed production
The following are factors limiting seed production of tropical pasture species: low inflorescence
density, delayed flowering and seed shattering, low seeding, susceptibility to disease and pest
attack, lodging and indeterminate growth habits
Post-Harvest Management
Crops may be grazed after seed harvesting. However, grazing should finish early enough to allow
crop development. This is most important in perennial plants like silver leaf and Greenleaf
desmodium which require e long period of growth before flowering.
Management of grasses and legumes for optimum seed production
 Management of all seed crops aims:
1. To establish an adequate, uniform plant population
2. Develop a dense cover excluding weeds
3. Have flowers of the same age, if possible
4. Ensure flowers develop into ripe seeds
For maximum seed yield, the crop cover should be developed well before the first flower appears.
Therefore any cutting or grazing of perennial forage species after seed harvesting should finish
when the big rainy season begins to allow complete recovery of the canopy before flowering.
Regular crop inspections are an important part of management. Problems such as weeds, insects,
pests and diseases can rapidly become serious, threatening the success of the crop.





 Managing Grass Seed Crops
Uniform ripening of a grass seed crop occurs if all the tillers are the same age. This is
achieved by cutting the grass at the start of its growth cycle. However, the clearing cut
should not be below 10 cm as this will restrict crop development. Available soil nitrogen
is a major factor affecting grass seed production. Ideally fertilizer nitrogen should be
applied as a single dressing soon after, the clearing cut this increases the number of seed
heads.
Very high rates of nitrogen fertilizer should be avoided as the result is crop lodging and
continued emergence of new seed heads, making recognition of peak maturity difficult.
Optimum nitrogen application for most grasses is 100kg/ha
The reason for applying a single application of nitrogen fertilizer is that it stimulates the
maximum number of early tillers and these produce most of the harvestable crop.
Splitting the nitrogen dressing can result in the production of another group of tillers of a
later age. Consequently the number of ripe seed heads on a single harvest day is reduced
as the tillers of a later age will have immature seed when the main crop is ready for harvest.
Split nitrogen applications may have a place on easily-leached sandy soils in high rainfall
districts. They ensure the nitrogen supply is adequate for seed filling in the latter stages of
the crop. (Note: Split nitrogen applications also have an important place in pasture
production where they are used to even out forage growth
32
 Managing Legume Seed Crops
 As in the case of grass seed crops, the ideal legume seed crop has synchronized flowering.
To achieve this all the crop canopy should be of the same age and growth stage. Then the
majority of seed will ripen at the same time. This is critical in the case of seed crops which
are harvested from the standing plant particularly if all pods, both immature and ripe, are
harvested at one time. A series of hand harvests is successful only in cases in which, firstly,
pods are large (allowing individual removal) and, secondly, ripe pods have conspicuous
distinguishing features, for example, the brown colour of ripe siratro pods compared to the
green purple colour of immature ones
Harvesting, threshing and storage condition of seeds
HARVESTING SEED CROPS
Time of Harvest: Even with good management, grass seed crops have a range of ages of seed
heads. Therefore it is necessary to judge the stage at which the maximum amount of grass seed is
ripe. This occurs when the rate of increase of ripe seed balances the rate of, shattering of seed from
older seed heads. Some legume seed crops also shatter, for example, siratro, axillaris. In such cases
seed must be harvested before it falls or, alternatively, swept up from the ground.
Manual Harvesting; Manual harvesting of grass and legume seed crops produces both larger
yields and better quality seed than machine harvesting. This is because manual harvesters are more
selective of what they harvest while machines harvest the whole crop, including ripe and unripe
seed and any weeds. Also much seed ends up on the ground with machine harvesting, both by
being knocked off the plant and by 'failure to thresh it completely.
Drying Legume Seed: Legume seed is best dried as soon as possible after harvest and as quickly
as possible. It is often sun dried, without damage to the seed. Usually legume seed has much lower
moisture content at harvest than grass seed. Consequently less drying is required.
Drying Grass Seed: Grass seed needs to be dried slowly to avoid damaging its viability. Thus it
must be dried in the shade. Spread the seed in a thin layer and turn it frequently (minimum once
per day) to avoid overheating.
Threshing: Threshing traditionally uses animals, the mucheka (mortar and pestle) or beating with
sticks. It is important to closely inspect the effect of threshing to avoid damage to the seed.
Labeling: each sack or bin must be labelled. The label contains the following information:
1. Cultivar
2. Date of harvest
3. Location of harvest
4. Sack or bin weight
5. Seed treatment
insecticide dressing)
(e.g.,scarification,
33
SEED STORAGE
Environment: The length of life of a seed in storage depends on the environmental
conditions of the store. For long term storages (5 years) seed should be stored at a low
temperature (15 °C maximum) and low relative humidity (4% maximum)
Storage Containers: Clean, dry seed should be stored in sacks on racks. This reduces
problems which occur with bulk storage on a bare floor, namely moisture absorption and
rodent and insect damage. For long term storage, especially of grass seed, sealed drums
or bins are suggested. Seed should first be dried to 8 to 10% moisture content and be free
of insects.
Storage Hygiene: This a complete approach to minimizing the populations of insects in
a seed store.
Managing Seed Quality: It is important to use seed before it dies in storage. For example,
if the environment in the seed store is suitable only for short term, then the seed should be
sown within 6 months. Check the date on the label on the sack. This will give an indication
of the seed quality. Older seed stocks should be used first. A germination test should be
used on any seed stored for 12 months or more. Also any seed of doubtful quality should
be tested.
CH 8. MANAGEMENT OF IMPROVED PASTURE
Establishing new forage sources is useful only if the plants are managed and used
efficiently. Newly sown forage needs time to establish. Thus careful management of
grazing and cutting is especially important in the first year. Uncontrolled grazing leads to
severe soil erosion. But, restricting grazing can mean reduced livestock numbers which is
usually unacceptable to farmers. However, with better feeding it is possible for farmers to
rear and care for a smaller number of better quality livestock. For this reason, cut-andcarry management is recommended wherever labor is available.
8.1.Grazing management
The objective of grazing management is to get long-term production of high quality
grazing which can maintain animals through both the wet and dry seasons. Both
overgrazing and under grazing have negative effects: unpalatable species can take over
and the productivity of the grazing is reduced.
The following are some rules of good grazing management:
 Grazing management should try to maintain a long-term balance between the
grasses and legumes, but short-term or seasonal changes are acceptable;
 Most pasture weeds can be controlled by grazing as well as by climbing legumes
and vigorous grasses;
 Grazing should be stopped when important species are forming seeds. However,
grazing of plants with mature seeds can encourage these plants to germinate as
the seed can pass through the gut intact and be sown’ in the dung of the animal;
 Animals should be allowed to graze as long as possible during the day so that as
much as possible of their dung and urine fertilizes the soil;
 Highland pastures should not be grazed lower than 10-15 cm and tropical pastures
not lower than 20-30 cm;
34
 Young animals and lactating animals should be allowed to graze first so they get
the best quality
Forage;
 Mixed grazing with cattle, sheep and goats can make better use of a mixed pasture
than only one type of animal; and rotational grazing can help in parasite control.
 Understanding grazing management principles is one of the keys to the ultimate
profitability of the operation.
Stocking rate: In its simplest form stocking rate is defined as the number of animals
grazing a unit area at a particular time.
Stocking density: the relationship b/n number of animals and area of land at any instant
of time.
Carrying capacity: number of animals a given pasture will safely support at a specified
level of animal gain or production for a given period of time (or the number of animals,
which can be safely sustained for a given period of time), i.e. it is the optimum stocking
rate.
Grazing pressure: the number of animals of a specified class per unit weight of herbage
(dry or ash-free) at a point in time. Also defined as the ratio of feed demand to feed supply.
Dry matter demand animal-1day-1x No. Animals
GP =
Dry matter available day-1 ha-1
Animal unit (AU): considered to be one mature (454 kg or 1000lb.) cow or the equivalent
based on average daily forage consumption of 11.8 kg (26lb.) dry matter per day.
Animal production ha-1 = production head-1 x No. animals ha-1
Herbage allowance: the weight of herbage (dry or ash-free) per unit of animal live weight
at a point in time.
Prescribed grazing schedule
A prescribed grazing schedule is a system in which two or more grazing units are
alternately deferred or rested and grazed in a planned sequence over a period of years. The
period of none grazing can be throughout the year or during the growing season of the key
plants. Grazing management is a tool to balance the capture of energy by the plants, the
harvest of that energy by animals, and the conversion of that energy into a product that is
marketable.
8.2. Basic grazing systems
1. Continuous grazing is defined as the type of management whereby grazing animals
are confined within a single enclosed pasture area for the entire grazing season it may be
a full a year. It is an extensive system of grazing in which the stock remains on the same
pasture area for prolonged periods of time. Within this system the pasture may be set
stocked or variable stocked.
Stocking rate should be low
A normal practice on rangelands and tropical savannah
Under grazed during the rains and overgrazed during the dry season
35
The disadvantages are buildup of tick and nematode infestation and lack of grazing
distribution
2. Soiling or Zero grazing: is the feeding of cut crops to housed stock
Advantage: a. efficient herbage utilization.
b. No loss due to trampling.
c. Uniform herbage intake.
d. Control bloat through wilting.
Disadvantage: a. High cost for labour or machinery.
b. Bedding required for housed stock.
c. Manure disposal is laborious.
3. Rotational grazing requires that the pasture is subdivided into a number of encloses
with at least one more enclosure than groups of animals. Rotational grazing system may
also be set stocked and or variably stocked.
A.Deferred rotational grazing: generally consists of multi pasture, multi herd systems
designed to maintain or improve forage productivity. Stock density is moderate, and the
length of the grazing period is longer than the deferment period.
B. Strip grazing: is a more intensive method of rotational grazing based on the use of
electric fence, which is moved forward once or twice a day. a fixed or variable number of
animals are given access to only part of a paddock by a movable fence in addition a
movable back fence may be used to prevent access to strips already grazed
Advantage: selective grazing is minimized resulting in more uniform consumption.
Applicability: a. highly productive and nutritious pasture.
b. high producing animals
C. Creep grazing (leader follower systems): is a rotational grazing system whereby the
highest producing animals (such as milking cows) are allowed the first grazing in a
paddock. This allows for maximum selection of highest quality forage. Once opportunity
for selection has declined then less demanding classes of livestock such as the dry dairy
cows or beef steers are moved in to graze the after math while the milking cows are moved
to fresh grazing.
36
3. APPLIED ANIMAL NUTRITION
Learning outcomes:
Upon successful completion of this course, students should be able to:
 Understand systems of feed nomenclature and different feed evaluation techniques;
 Classify feedstuffs based on their nutritive value;
 Analyse chemical composition and digestibility of feedstuffs;
 Determine nutrient requirements and formulate balanced rations for various classes of
livestock;
 Involve in the process of feed conservation and processing; and
 Understand the role and application of biotechnology in animal nutrition.
CH 1- Introduction
1.2. Nomenclature of Feedstuffs
Purpose of Nomenclature of Feedstuffs- To have a common language of understanding of
some common feedstuffs, different systematic naming is used.
An ideal feed name should precisely,
 Describe that feed genotypically and morphologically
 Define its quality or grade if applicable, and indicate its place in the classification of
feeds i.e. it should give information that makes its chemical composition more
intelligible to the nutritionist
 The eight potential parts of NRC names,
1. Origin: The first term of the NRC name refers to the parent substance from which the
material that is eaten originates
2. Variety or kind: If the variety or kind of an original source is nutritionally significant,
this information is included as the second term of the name.
3. Part eaten: The third component of the feed name is the actual part of the parent
material that is consumed.
4. Processing and treatments: Some parts of the parent feed material has had no
processing, example pasture grass. But there are a lot of feeds which have had
something done to them to preserve or to make them more palatable
5. Stage of maturity: Stage of maturity applies to roughage products, generally speaking.
But with roughages this perhaps is the most important factor in determining their
nutritive value
6. Cutting or crop number: This part of the name refers to weather the roughage material
was first cut or first crop, second cut, third cut, etc
7. Grade or quality designation: Many products in developed countries such as hay and
grains have for many years been graded by official government standards. These
different gradings are significant in interpreting the nutritive value of the product
8. Classification: This refers to feed classes. This component according to the NRC
classification of feeds is listed into 8 classes.
37
Table 1. NRC classification of feeds
Code and class
1. Dry forage or roughage
Typical products
Hay, Straw (stems and leaves of grains), Seed
hull (Outer covering of Grains and other seeds),
Fodder (aerial pt w ears, husks, or heads), Stover
(aerial pt wo ears, husks or heads)
2. Succulent forages or roughages Pasturage, Range plants, Soiling crops ( green
(succulent pasture)
forage crops cut and fed in fresh condition to
stock often called soilage)
3. Silages
Grain crop silage, Grass silage, Haylage
4. Energy feeds
Grains and seeds (low Cellulose, high cellulose,
Mill by-products (low Cellulose, high cellulose),
Fruits, Nuts, Roots
5. Protein supplements
Animal by- products, Plant by-products, Avian
by-products, Marine by-products
6. Mineral supplements
Natural or pure elements
7. Vitamin supplements
Natural or pure elements
8. Additives
Flavors,
hormones,
coloring
materials,
antibiotics
Example.
Table 2. Components of the NRC feed nomenclature
Example
Component
Feed 1
Feed 2
1. Origin
Alfalfa
Corn
2. Variety
Ranger
Yellow
3. Part
Leaves
grain wo germ
4. Process
dehy, pltd
Grnd
5. Maturity
early blm
-6. Cutting
Cut 1
-7. Grade
US 1
-8. Class
(1)
(4)
dehy = dehydrated; pltd = pelleted; wo = without, grnd = ground; blm = bloom; 1 =
dry forage; 4 = energy feed.
 When we write NRC names using the information given in table 2, it looks
like: Feed 1: Alfalfa, ranger, leaves, dehy pltd, early blm, cut 1, US 1, (1) Feed
2: Corn, yellow, grain wo germ, grnd, (4)
CH 2- GENERAL CHARACTERISTICS OF COMMON FEEDSTUFFS
Purposes of feed classification Is to group feeds of somewhat similar nutritional characteristics.
 To have a clear understanding of the character of different feeds
 To formulate ration
2.1.
Roughage
38
Characterized by; Being low in nutritional value- contain greater than 18% CF, Contain low
energy and crude protein content , as roughages are generally bulky feeds, their intake is
limited.
2.1.1. Dry roughage
A. Hey
1.
2.
3.
Leguminous hay: It has a higher percentage of digestible nutrients.
Non-leguminous hay: Non-legume hays made from grasses are inferior to
legume hays.
Mixed hay: Hay prepared from mixed crops of legumes and non-legumes
is known as mixed hay.
B. Straw
1. Cereal straws
2. Pulse straws
C. Husks:
1. Rice husk
D. Stovers:
1. Sorghum stover.
3. Groundnut straw
4. Rape straw
2. Groundnut husk
3. Maize husk
2. Maize stover
2.1.2. Green roughage
Cultivated fodder
1)
2)
Cowpea
(Vigna
unguiculata)
Sorghum(So
rghum
bicolor)
3)
4)
Maize (Zea
mays)
Soybean
(Glycine
max)
5)
6)
Lucerne
(Medicago
sativa)
Oat (Avena
sativa)
Grasses
1. Napier grass
2. Rhodes grass
3. Perennial rye grass
4. Guinea grass
Tree leaves
1)
Bamboo leaves
2.2.
Concentrates
2)
Neem (Azadirachta indica)
On the basis of the crude protein content of air dry concentrates, these are classified
as either energy rich concentrates when crude protein (CP) is less than 18% or
protein rich concentrates when the CP value exceeds 18%.
2.2.1. Energy concentrates
 Feeds used as energy sources (energy supplement feeds).
These are described under the following categories:
39
1. Grains and seeds
3. Molasses
2. Milling by-products
4. Roots and tubers
1. Grain and Seeds
Grains are seeds from cereal plants, members of the grass family called Graminaea.
Cereal grains are essentially carbohydrates, the main component of the dry matter
being starch, which is concentrated on the endosperm.
2. Milling by-products
When grain is processed for flour production, there are a number of products that left out
as a by-product.
Wheat milling by-products
A. Wheat bran (Furshika) - Contains- about 10% (8.5-12% CF), higher than the
kernel, it has around 67% TDN, In terms of CP it contains about 16.4% (16-18%
CP). It is one of richest source of phosphorous but low in calcium.
B. Wheat shorts (Furshikelo) - since it has the germ, the product is expected to have
higher CP content (greater than 18% CP or is around 21-22% CP), 77% TDN.
C. Wheat middlings- Compared to wheat bran, wheat middlings contain a lower fiber
and higher flour content (high in TDN). The minimum CP content is 10-14% and
maximum CF content is 9.5% for this by-product.
3. Molasses
Molasses is highly palatable and an excellent source of energy. In addition to its
use as energy feed, is also used 1)
As appetizer 2) To reduce dustiness of
a ration 3) As a binder for pelleting 4) To stimulate rumen microbial activity
and 5) To supply unidentified factors.
Types of molasses
1. Cane molasses
2.
Beet molasses
3. Citrus molasses
4. Roots and tubers
1. Roots- fodder beet, sugar beet and turnip. The main characteristics of roots are
their high moisture content 75-90% and low crude fiber content.
2. Tuber: Tubers differ from root crops in containing starch
A.Cassava root (Manihot esculenta)
C.Sweet potato (Ipomoea batatas)
B.Potato (Solanum tuberosum)
D.Carrot (Daucus carota)
2.2.2. Protein concentrates
Protein supplements are arbitrarily defined as having at least 20% CP. They can be of
animal origin, plant origin or unconventional protein supplements.
40
I.Animal origin protein supplements
1.
Meat meal
2.
Fish meal
3.
Blood meal
II. Plant origin protein supplements
There are two major methods of processing of oil seeds to produce oil or for extraction
of oil from oil seeds. These are:
A.
Expeller method
B.
Solvent extraction method
Some oilseed cakes or oilseed meals
Oilseed cakes and meals are the residues remaining after removal of the greater
part of the oil from oilseeds. The residues are rich in protein and most are
valuable feeds for livestock.
1.
2.
3.
Peanut meal/groundnut meal
Cottonseed meal
Sunflower meal or sunflower
seed oil meal
4.
Safflower meal or safflower
seed meal
5.
Rapeseed meal (canola meal)
2.2.3. Minerals supplement
6.
7.
8.
Linseed meal or flaxseed
meal
Soybean meal or soybean oil
meal
Noug cake or noug seed
meal or niger seed cake
 Numerous minerals are essential for proper animal nutrition. In addition to their
metabolic functions, the macro-minerals are necessary for tissue structure (e.g.
calcium and phosphorous in bone or egg shells) and for milk secretion.
 Macro-minerals Micro-mineral calcium iron phosphorus copper sodium zinc
chlorine manganese potassium cobalt sulphur iodine magnesium selenium 20
molybdenum chromium. Bone meal, limestone and many mineral supplements
are available from commercial feed suppliers.
2.2.4.
Vitamins supplement
 Vitamins function as cofactors or enzyme activators in metabolic processes so are
necessary for all general body functions and maintenance of health.
 All green, growing plants contain carotene which animals can convert into vitamin
A.
 Supplemental vitamin A may be necessary to ensure an adequate supply
 Diets for very young calves and all non-ruminants may require some
supplementation with B vitamins.
41
2.3.
Feed additives
Feed additives are non-nutritive substances added to feeds to improve the efficiency of
feed utilization and feed acceptance, or to be beneficial to the health or metabolism of the
animal in some way. Feed additives are classified into four categories based on their
principal biological and economic effects.
I.
Additives that influence feed stability, feed manufacturing and properties of
feeds
A. Antifungal agents
Antifungal agents are used to prevent fungal or mold growth in stored feed ingredients
and mixed feeds (feed stability). Example: propionic acid and its salt (Sodium or Calcium
propionate) at levels of approximately 1% of the grain or diet. Others include Sodium
diacetate, Sorbic acid and Gentian violet.
B. Antioxidants
These are preservatives that prevent the oxidation of fats or rancidity (stability and
properties of feeds. Example: Vitamin E and Vitamin C (natural antioxidants). Synthetic
antioxidants include ethoxyquin (santoquin), butylated hydroxytoluene (BHT) and
butylated hydroxyanisol (BHA).
C. Pellet binders
Pelleting increases the density of feeds, often resulting in increased feed intake and
improved growth and feed efficiency. Pelleting reduces feed wastage and eliminates
sorting of ingredients by animals, reduce dust, and increase ease of feed handling.
Example: Bentonite clay mineral which is most widely used as pellet binder
(montmorillonite or hydrated aluminium silicate) with iron exchange and surface active
properties
II. Additives that modify animal growth, feed efficiency, metabolism and performance
A. Feed flavors
Feed flavors are used to increase the acceptance of diets of low palatability, increase intake
of palatable diets and increase intake of diets during periods of stress such as weaning
(feed efficiency). Example: Molasses, sucrose, glucose, saccharine. The flavors tend to
mask flavor of other ingredients like rapeseed meal. Molasses is also used to decrease
dusty nature of feeds.
B.
Digestive modifiers
1. Enzymes
The main potential of enzyme addition to feeds appears to be for digestion of substances
that the animals are intrinsically incapable of digesting. For instance, the addition of
cellulase for non-ruminants for cellulose digestion though not reaches practical stage. βglucanase to swine and poultry to digest β-glucan, pentosanase to digest pentosans (major
ant nutritional factor in rye).
42
2. Buffers
This is a salt of week acid or base that resists a pH change. Buffers are used extensively
for ruminants fed high concentrate diets and are particularly useful in the adaptation period
from high roughage to high concentrate diets and help in the prevention of lactic acidosis.
Example: Sodium bicarbonate, Potassium bicarbonate, Magnesium bicarbonate, calcium
carbonate and bentonite.
3. Isoacids
These are commercially produced branched chain volatile fatty acids like isobutyric acid,
2-methylbutyric acid, isovaleric acid, valeric acid which are required for the synthesis of
branched chain amino acids like valine, leucine, isoleucine and proline.
4. Probiotics
This term is coined to describe microbes used as feed additives. They are defined as live
microbial feed supplements which beneficially affect the host animal by improving its
gastrointestinal microbial balance. Such effects could be due to the enzyme released by
the microbes. Example, Lactobacillus acidophilus, Streptococcus faecium, yeasts etc.
5. Antibloating agents
These feed additives are effective in preventing frothy bloat which is associated with the
consumption of lush legume pasture and rapid release of fermentable carbohydrates and
soluble proteins in the rumen. Example, poloxalene
6. Salvation inducers (sialagogues)
These are substances that increase the production of saliva as inadequate saliva secretion
occurs when concentrates are fed which leads to metabolic disorders and suboptimal feed
utilization. Example, salframine
7. Defaunating agents
Defaunation is the process of treating a ruminant animal to eliminate its rumen protozoa
as protozoa may feed rumen bacteria and small feed particles they may reduce feed
utilization efficiency. Example, Copper sulfate, nonionic and anionic detergents
C. Metabolism modifiers
1. Hormones: certain synthetic or natural hormones could be added to the ration of
animals to improve animal performance. Natural hormones like androgen (testestrone),
estrogen, growth hormone, progestrone stimulate growth of animals. Synthetic hormones
like diethylstibestrol (DES) are a synthetic estrogen which is important particularly in
steers but is banned from use in USA
43
2. Beta-adrenergic agents (repartitioning agents): These are norepinephrine
(noradrenalin) analogs that stimulate beta-adrenergic receptors. These result in a
repartitioning of nutrients from fat to protein synthesis causing increased muscle mass and
decreased body fat.
CH 3. CHEMICAL COMPOSITION ANALYSIS
3.1
The proximate (Weende) method of analysis
Weende system is principally devised to separate carbohydrates into two broad
classifications: crude fiber and nitrogen free extract. According to this method of
analysis feedstuffs are partitioned into six fractions.
1.
Water/moisture
4.
Crude protein (CP)
2.
Ether extract (EE)
5.
Ash, and
3.
Crude fiber (CF)
6.
Nitrogen-free extract (NFE)
Limitations of proximate analysis:
44
 It is not precise in the quantification of the available and unavailable parts of the feed or it
does not accurately fractionate the carbohydrate fraction into the true fibrous and nonfibrous components.
 The CF system fails to distinguish between plant cell contents and cell wall materials
because the analytical procedure results in the solubilization of portions of the cell wall or
less digestible constituents.
 Errors in NFE fraction are further caused by double determination of some constituents in
different fractions.
3.2.The Van Soest method of analysis
This is the second method of analysis developed to get a better quantification of the nutritional
content of feeds. Van Soest tried to develop chemicals that will exactly partition cells into two.
These chemicals are similar to the gastric juice of monogastric animals and called neutral detergent
solutions which divide the cell into cellular and cell wall parts.
 Cell contents - correspond to the digestible or soluble fraction. They are soluble in neutral
detergent solution and are 98% digestible and not affected by lignification.
 Cell wall constituents - which include the indigestible fibrous fraction for monogastrics. Cell
wall constituents or neutral detergent fiber (NDF) are insoluble in neutral detergent solution
and only partially available to species of ruminants.
 After measuring the cell wall fraction Van Soest tried to differentiate monogastrics from
ruminants, and he used acid detergent solution and obtained acid detergent insoluble fiber
(ADF) and acid detergent soluble. The fraction soluble in acid detergent solution is acid
detergent soluble. This fraction shows the part of the cell wall which could be utilized by
ruminant animals due to the presence of microorganisms.
3.3. Modern analytical methods
3.3.1. Near infrared reflectance spectroscopy
Near infrared reflectance spectroscopy-NIRS method of analysis is an instrumental method for
rapidly and reproducibly measuring the chemical composition of samples with little or no sample
preparation.
It is based on the fact that each of the major chemical components of a sample has near infrared
absorption properties which can be used to differentiate one component from the other. The
summation of these absorption properties, combined with the radiation-scattering properties of the
sample, determines the diffuse reflectance of a sample. Therefore, the near infrared diffuse
reflectance signal contains information about the composition of the sample. The compositional
information can be extracted by proper treatment of the reflectance data.
45
3.3.2. Chromatography
Chromatography-Derived from the Greek word Chroma meaning colour, chromatography
provides a way to identify unknown compounds and separate mixtures. It can be used at various
stages of the food chain from determining the quality of food to detecting additives, pesticides and
other harmful contaminants
CH 4. DIGESTIBILITY
Digestibility refers to the disappearance of feed or food from the gastrointestinal tract. In other
words, digestibility is the degree of degradation of feedstuffs in the gut. Digestibility coefficient
is therefore, the proportion of feed which is not excreted in the feces and which is therefore,
assumed to be absorbed by the animal thus available for metabolism. Therefore, digestibility is an
essential feature of feedstuff evaluation. There are different methods of estimating digestibility.
This includes:
4.1.In Vivo/conventional
This is a direct measurement that involves keeping an animal in a metabolic crate and measuring
the feed intake and the fecal output. The feed and feces are analyzed for nutrients of interest to
determine nutrient digestibility
% Digestibility = DM in feed – DM in feces x 100
DM in feed
% Digestibility = Nutrient intake – Nutrient in feces x 100
Nutrient intake
Example: A steer consumes 10 kg of hay which has 90% DM, and excreted 3kg of
DM in the feces. What is the digestibility of the hay DM?
% Digestibility = DM in feed – DM in feces x 100
DM in feed
= (9 – 3) x 100
9
= 66.6%
Shortcoming of conventional method
 It is laborious and time consuming.
 we get the apparent digestibility rather than true digestibility
46
4.2.In vitro/laboratory method
The digestibility of feeds for ruminants can be measured quite accurately in the laboratory by
treating them first with rumen liquor and then with pepsin. During the first stage of this so called
two-stage in vitro method, a finely ground sample of the feed is incubated for 48 hours with
buffered rumen liquor in a tube under anaerobic conditions. This first stage involves test tube
containing buffer solution, the rumen microbes and test forage incubated at a body temperature
under anaerobic condition. The buffer solution represents the artificial saliva and buffers the acid
produced during fermentation.
IVDMD % = Initial dry sample wt – (Residue – Blank) x 100
Initial dry sample wt
The major sources of errors/variations are:
1.
Variation in the microbial population. this is brought by the diet of the donor
animals, animal to animal difference, inoculum processing
2.
3.
Variation due to different storage, grinding and processing techniques in sample preparation
Differences attributable to the fermentation medium such as sample to inoculum ratio, buffer
solution and nutrients in the medium
Procedural variation such as length of fermentation and laboratory errors
4.
4.3.In Sacco method/nylon bag techniques
This method is also called the nylon bag or in situ method of digestibility determination. In this
method instead of doing laboratory estimation of digestibility, fistulated animals are needed. Feed
samples 2-3g will be placed in small bags made up of permeable synthetic fabrics of standard pore
size of 30-50 microns which will be inserted into the rumen through the cannula and incubated
there for 48–72 hours. After each bag will be withdrawn, washed and dried to determine the
quantity of feed DM remaining as undigested material. Digestibility will then be determined by
difference. Using the formula:
Disappearance = (SWa - BW) x DMa - (SWb - BW) x DMb
(SWa - BW) x DMa
Where: SWa = Weight of the original sample + nylon bag
BW = Weight of empty nylon bag
SWb = Weight of the sample + nylon bag after incubation
DMa = Dry matter of feed sample
DMb = Dry matter of residue sample.
In the nylon bag method there are problems in its use arising particularly from the need to select
an appropriate period of incubation. The other problem of this technique of digestibility estimation
47
is that, the value tells us the rumen digestibility since we simulate what is happening in the rumen.
But digestion occurs from ingestion to excretion.
4.4.Indicator method
Sometimes it becomes impractical to measure directly either feed intake or fecal output, or both.
For instance when animals are fed in a group, it is impractical to measure the intake of each
individual. Digestibility is however can still be measured if the food contains certain substances
which are known to be completely indigestible. These substances are called indicators. There are
two types of indicators. These are:
A.
Internal indicators: These are indicators found within the feed
B.
External indicators: These are indicators that we add to the feed
% Digestibility = % indicator in feces - % indicator in feed x 100
% indicator in feces
% Digestibility for nutrients = 100 - % indicator in feed x % nutrient in feces x 100
% indicator in feces x % nutrient in feed
4.5. Factors that affect digestibility
Digestibility results of the same feed may be variable because of different factors. These include:
1.
Level of feed intake
5.
Nutrient deficiency
2.
Frequency of feeding
6.
Feed composition
3.
Animal factor
7.
Feed processing or
preparation
4.
Digestive disturbance
8.
Ration
composition
(effects of combining
different feeds)
CH 5. EVALUATION OF ENERGY AND PROTEIN VALUES OF FEEDS
5.1. Energy Values of Feeds: Energy value is the inherent power of feeds to supply energy
essential for reproduction, maintenance, growth and milk production of animal. The ability of a
feed to supply energy is therefore of great importance in determining its nutritive value in the
evaluation of feeds.
5.1.2. Measures of the energy requirement of animals
1. TDN (Total digestible nutrient): TDN is an energy which could be received from digestible
parts of feedstuffs.
%TDN = %DCP + %DCF + %DNFE + (%DEEx2.25)
48
2. GE (Gross energy): The quantity of the chemical energy present in a food is measured by
converting it into heat energy, and determining the heat produced. This is done by oxidizing
the food or by burning it
3. DE (Digestible energy): The 1st source of loss of energy to be considered is the energy
contained in the faeces. The apparent digestible energy of the feed is the difference of GE
less the energy contained in faeces (GE-FE).
4. ME (Metabolically energy): This is the digestible energy less the energy lost in the urine
and combustible gases (ME = DE – UE – GPD). The energy of urine is present in nitrogencontaining substances such as urea, hippuric acid, creatinine, and allantoin, and nonnitrogenous compounds as glucuronates and citric acid.
5. NE (Net energy): ME doesn't account for the energy lost as HI, and the deduction of HI of
a food from its ME gives the NE values of the feed (NE = ME – HI). This is that energy
which is available to the animal for useful purposes, for body maintenance and for the
various forms of production
5.2 Protein values of feeds: Feeds can be crudely evaluated as source of protein which can be
applicable for all species of livestock.
5.2.1. Measures of protein quality
1.
Crude protein: This assumes all proteins contain 16% nitrogen and all nitrogen is found as
protein. Most of the. Nitrogen required by the animal is used for protein synthesis and most
food nitrogen is also present as protein. So, CP is used as a measure of protein.
2.
True protein: When true protein needs to be determined, it can be separated from NPN by
precipitation with cupric hydroxide or in some plant material by heat coagulation
3.
Digestible crude protein: The crude protein in the feed minus protein in the feces indicates
digestible crude protein.
Measures of protein quality for Mongastric animals
1.
Protein efficiency ratio (PER)
This is defined as weight gain per unit weight of protein eaten.
PER = Gain in body wt. (g)
Protein consumed (g)
2.
Net protein ratio (NPR)
NPR = Weight gain of TPG – Weight loss of NPG
Weight of protein consumed
49
Where, TPG = Group fed on test protein; NPG = Non-protein group, NPR is claimed to give more
accurate results than PER and used to compare two groups fed and not fed.
3. Biological value (BV)
This is the proportion of N absorbed which is retained by the animal and used for the synthesis of
body tissues.
BV = N intake – ((Fecal N – MFN) – (Urinary N – EUN))
N intake – (Fecal N – MFN)
Measures of protein quality for ruminants
In UK, feeds are evaluated in terms of rumen degradable protein (RDP) that is available to the
microbes and undegradable dietary protein (UDP) which escape rumen fermentation but be
degraded in lower gut.
CH 6. VOLUNTARY FEED INTAKE AND ITS REGULATION
6.1. Factors affecting feed intake
Animal related factors
1), Physiological Status of the Animal
 Young growing and older animals that need to restore their depleted body tissue
50
 Pregnant animals
 Lactating animal
Animal Genotype and Size: Under the same nutritional and environmental conditions,
potential intake of a given animal is determined by its genetics.
2). Feed characteristics
Physical and Chemical Factors: Physical factors refer to these characteristics of a feed
that affect intake by influencing gastrointestinal volume following ingestion and the rate
at which that occupied volume is reduced via digestion and onward passage
Physical form: Mechanical grinding of roughages can partially destroy the cell wall
structural organization thereby increasing rate of ruminal breakdown and increased intake.
Nutrient Balance: Intake may also be depressed when the feed is deficient in nutrients
that are critical for the activities of rumen microbes like proteins, minerals (like sulphur,
phosphorus, sodium and cobalt), vitamins or amino acids.
3). Environmental Factors
Environmental temperature: Both high (heat stress) and low (cold stress) environmental
temperatures can affect intake in farm animals. Heat stressed animals reduce their feed
intake in order to reduce increased heat production associated with feed consumption
Housing: Provision of shade in hot climates increases intake by reducing the impact of
heat stress.
Disease: Diseased animals reduce their intake and this is one of the first sign of many
diseases.
Availability of Water: both the amount and time of water intake are closely related to
food intake.
6.2 Feed intake regulation
6.2.1. Feed intake in Mongastric animals
1. Control centers in the central nervous system (CNS)
a.
b.
Feeding centre (lateral hypothalamus) - which causes the animal to eat food.
Satiety centre (ventromedial hypothalamus) - which inhibit eating when receiving
signal from the body as a result of consumption of food.
c. Short-term control
2. Chemostatic theory
The absorption of nutrients from the digestive tract, and the presence of nutrients in the
circulating blood, constitutes a set of primary signals which may in turn influence the
satiety centre of the hypothalamus. A number of blood constituents have been suggested
as possible signals including glucose, VFA, peptides, amino acids, vitamins and minerals.
Of these, glucose or the glucostatic theory has received the most attention.
51
3. Thermostatic theory: This theory proposes that the animal eat to keep itself warm and
stop eating to prevent hyperthermia. Heat is produced during the digestion and
metabolism of food and it is considered that this heat increment could provide one of
the signals used in the short term regulation of food intake.
4. Long-term control - Lipostatic theory: The long-term preservation of constant body
weight combined with an animas desire to return to that body weight if it is altered
by starvation or forced feeding implies that some agents associated with energy
storage acts as a signal for a long term regulation of feed intake. One suggestion is
that this might be the fat deposition.
4. Sensory appraisal: The sense of sight, smell, touch and taste play an important role in
stimulating appetite. But this is more important in man than farm animals.
5. Physiological and physical factors
i.
Metabolic
iii.
body weight
iv.
ii. Distension
v.
Lactation
vi.
Nutrients
deficiency
vii.
Choice feeding
Pregnancy
Exercise
6.2.2. Feed intake in ruminants
1. Chemoatic theory: The digestion end products in ruminants are VFAs. A more
plausible chemostatic control mechanism may involve the 3 major VFAs. When
acetate and propionate are high, they send signals to CNS so that animal will stop
eating. So, when level increases, intake decreases or ceases. If the level decreases, the
animal will fell hungry and search for food.
2. Thermostatic theory: Ruminants respond to environmental temperature in the same
way as monogastric animals, in that prolonged exposure to heat lowers food intake
and continued exposure to cold increase it.
3. Lipostatic theory: Mechanism is believed to be similar to monogastric animals. There
is evidence that fatness reduces intake in cattle
4. Sensory appraisal: The senses do not appear to have much influence on the overall
control of voluntary feed intake in ruminants, but are important in their grazing habits
and eating behavior.
5. Physical factors: There are two important factors:
a. Size of the reticulo-rumen
b. Digestibility and rate of disappearance of feed from the gut
6. Physiological factors
a. Compensatory growth
c. Lactation
b. Pregnancy
52
CH 7. FEEDING STANDARDS AND NUTRIENT REQUIREMENTS
The statement of the amount of nutrients required by an animal is called feeding
standards.
7.1. Factors affecting nutrient requirement
Nutrient requirement of animals are affected by the following factors
1. Breed/Type of
animal
2.
Age
3. Sex
5. Weather condition
4.Physiological
condition
6. Production System
7.2.Nutrient requirements for different activities
Maintenance and growth: Maintenance requirement of nutrients can be defined as the
quantity which must be supplied in the diet so that the animal experiences neither net
gain nor loss of that nutrient.
Nutrient requirement for growth
Energy requirement for growth
By undertaking feeding trial experiments scientists come up with certain formula useful
to estimate growth requirement of animals in terms of energy.
TDN (lb/day) = 0.036 W0.75 (1 + 0.57)
DE (kcal/day) = 76 W0.75 (1 + 0.58)
ME (kcal/day) = 62 W0.75 (1 + 0.60)
NE (kcal/day) = 32 W0.75 (1 + 0.45)
Protein requirement for growth
Protein requirement is very high but gradually decline as age increases. At certain point
the animal requirement for protein will be the same as for maintenance i.e. at the stage
when the animal stops growth, in terms of protein deposition. Then after the increase will
be a result of fat deposition. In monogastric animals in addition to the general need for
protein there is also a requirement of the essential amino acids
Mineral and vitamin requirement for maintenance and growth
Minerals: Animals deprived of mineral elements continue to excrete minerals in the urine,
feces and through the skin. These endogenous losses are often small compared to content
in the body. This loss of mineral is the amount that is used for maintenance.
Vitamins: There are no estimates of the endogenous losses of vitamins to base factorial
estimates of vitamin requirement. Standards must therefore be derived from feeding
trials.The main criteria to be considered are growth rate and freedom from signs of
deficiency. Deficiency signs can be detected either by visual examination of the animal or
by physiological tests such as determination of the vitamin level in the blood.
53
Reproduction
Reproductive cycle may be considered as consisting of three phases.
I. Production of ova and
spermatozoa
ii.
Pregnancy
iii.
Lactation
1. Egg Production: Factorial can be sued by adding gram of egg produced and the
content of each nutrient in the egg plus maintenance requirement plus gain.
2. Growth of fetus: The quantities of the nutrients deposited daily in the uterus can be
determined by weighing and analyzing uteri taken from animals killed at various
stages of pregnancy.
3. Lactation: This is the nutrient requirement for milk production. The requirement for
lactation depends on the amount and composition of milk being produced. Milk
protein, lactose, milk fat, minerals and vitamins content of the milk will dictate the
amount of nutrients required.
CH 8. RATION FORMULATION
The most important part in feeding animals is formulating a ration that will meet the
requirement of the animals for the sought purpose. Ration is a feed allowance for a given
animal during a day. The feed may be given once or in several portions.
A balanced ration is one which provides animals with the proper proportions and amounts
of all the required nutrients.
A well balanced ration should have the following desirable characteristics:
1.
2.
3.
4.
5.
The ration should be well balanced to meet the requirements of the animal
The feed must be palatable,
Variety of feeds in the ration,
The ration should be fairly laxative
Rations for ruminants should be fairly bulky.
6. The feed must be properly prepared
7. Economical:.
8. Compound feeds should not have negative influence on quality of milk, beef, pork,
eggs, poultry meat, etc.
Considerations in ration formulation
A. Nutritional factors
1. Dry matter
6. Vitamin A
2. Protein
3. Energy
4. Ca and P
5. Other minerals
54
7. Other vitamins
B, Economic factors: Feeds are not always priced in accordance with their nutritive value. Some feeds
may be a cheaper source of nutrients than other feeds with any given set of prices. To compare
feeds as economical sources of nutrients, it is not sufficient to compare them in terms of price per
kg or quintal
C.
Other factors: Stress due to temperature, parasite and disease (unfavorable environments)
has to be considered in balancing ration.
In order to formulate a ration, we have to have information about the following points:
1. Chemical composition of the available feed staff or nutritive value has to be known. Feeding
standards or nutrient requirements of the animals have to be known.
2. Apart from the above two basic factors the following points have to be considered
%TDN of each ingredints
% DCP
Price/100 kg
Price/%TDN
Price/%DCP
Safe maximum %
Absolute maximum %
Safe maximum %: is the percentage of a particular feed staff which can be safely included or this
is the level that is recommended.
Absolute maximum %: is the percentage of a particular feed staff beyond which you should not
include. We should never pass the percentage indicated as absolute maximum % and is greater
than safe maximum %.
Methods of ration formulation
To formulate a ration
I.
List the available feed stuffs and their data like nutrient content, price, safe maximum
percentage and absolute maximum percentage.
II. Fix the requirement of the animal. For energy the optimum value is mostly considered and
protein minimum value is considered as protein is expensive.
III.
Algebraic calculation
Assume that we use corn and soybean with % CP 8.5% and 44%, respectively. If the protein
requirement of swine is 15% and slack space is 2.5%. The other component will be 97.5%. To
calculate the combination of the two diets that will provide 15% CP, follow the following
procedure.
For 100kg mixed feed,
The amount of soybean = 97.5 - x
Let the amount of corn = x
Kg of corn protein = 0.085x
55
Kg of soybean protein = 0.44(97.5 - x)
x = 78.59 for corn
Kg corn + soybean = 15 kg
97.5 – x = 18.91 for soybean
0.085 + 0.44 (97.5 - x) = 15
Check the calculation
18.91 x 44 % CP = 8.32 from soybean
78.59 x 8.5% CP = 6.68 from corn
Total percentage = 15.0
8.1.1
Pearson's square method.
Rather than using algebraic equation shown above, the Pearson's square can be used which
basically is the diagrammatic version of the equations. Therefore, in this case,
CP% of SBM, 44%
6.5 parts
15%
Desired
CP% of corn, 8.5%
29 parts
Total
35.5 parts
CP% SBM = (6.5/35.5) x100 = 18.3
CP% Corn = (29/35.5) x100 = 81.7
Total percentage = 100
Note that this answer is slightly different because no slack space was used. To recalculate with a
slack space, we would say that we want all the 15 parts of CP to be in the 97.5% of corn and
SBM. Therefore, for a 100% mixture of corn and SBM the CP% should be 15.39 so that when
97.5% of this mixture is used, it will provide 15% CP.
56
CP% of SBM, 44%
6.89 parts
15.39%
28.61 parts
Required
CP% of corn, 8.5%
Total
35.5 parts
CP% SBM= (6.89/35.5) x100 = 19.4
CP% corn = (28.61/35.5) x100 = 80.6
Total percentage = 100
Kg SBM used per 97.5 kg of the diet = 19.4 x 0.975 = 18.91
Kg corn used per 97.5 kg of the diet = 80.6 x 0.975 = 78.59
The principle of total mixed ration
The term total mixed ration (TMR) – The practice of weighing and blending all feedstuffs
into a complete ration which provides adequate nourishment to meet the needs of animals.
Each bite consumed contains the required level of nutrients protein, minerals and
vitamins) needed by the animals
CH 9. FEED CONSERVATION AND FEEDING STRATEGIES
 Forage conservation
 The need to conserve fodder
 To preserve feed when it is available in excess.
 To maintain optimum nutritional value of fodder.
 To shift available feed from the present to the future.
 To move feed from one location to another location.
 To assist pasture management
Methods of Conservation
9.1.1. Hay making
The basic principle of hay making is to reduce the moisture concentration in the green
forages sufficiently as to permit their storage without spoilage or further nutrient losses
Harvesting, curing and baling of hay
57
Leguminous fodder crops should be harvested at their flower initiation stage or when crown buds
start to grow, while grasses should be harvested at their pre-flowering or flower initiation stage.
Harvesting should be done preferably when air humidity is low. The harvested forage should be
spread in the field and raked a few times for quick drying. The dried forage should be collected
and baled when the moisture concentration becomes lower than 15 per cent. Baling the hay helps
in storage and requires less space.
Losses in hay making
1. Respiration
3. Leaching
2. shattering and dropping of leaves,
1.1.2. SILAGE MAKING
Silage is the material produced by the controlled fermentation of a crop of high moisture content.
Ensilage is the name given to the process, and the container, if used, is called the silo. Almost any
crop can be preserved as silage, but the commonest are grasses, legumes and whole cereals,
especially wheat and maize. The basic principle of silage making is to convert the sugars in the
ensiled fodder into lactic acid; this reduces the pH of the silage to about 4.0 or lower, depending
on the type of process
Losses in silage making
The losses resulting from silage making are the sum of respiration losses, fermentation losses,
effluent losses, and losses due to prolonged fermentation and moulding
Guidelines for preparing and using a silage pit
Harvesting, Silo preparation, Closing the silo, Opening the silo
Forage used for silage making
Maize, oats and sorghum are important fodder crops that are rich in carbohydrates. During
periods of abundant green fodder availability, they can be chopped and ensiled to produce silage
for feeding during scarcity periods
Use of additives in silage making
The benefits of using additives should be seen in comparison to the costs of applying them. The
most common ones are organic acids, molasses and preservatives. Most of the undesirable bacterial
activity can be prevented by adding an organic acid to the crop.
Storage structures for silage
A silo is a structure designed to store and preserve high moisture fodder such as silage. The
selection of a silo is made on the basis of required capacity, climatic conditions and economic
considerations. Different silo types are used to conserve and store fodder:
o horizontal silos, such as trench silos and bunker silos;
o vertical silos, such as pit silos and tower silos
CH 10. FEED PROCESSING TECHNOLGY AND STORAGE
10.1. Purpose of processing
58
Feeds may be processed to alter the physical form or particle size, to prevent spoilage, to isolate
specific parts, to improve palatability, or inactivate toxins or anti-nutritional factors, to change
moisture content, to improve digestibility, hence intake. In some cases feeds my processed to
improve the capability of handling.
10.2. Methods of processing
10.2.1 Processing grains
i. Cold processing
1. Grinding- The most common, simple and cheapest method
Grinding generally improves digestibility of small, hard seeds
2. Soaked grains/reconstitution- It involves adding water to matured, dried grains to raise
the moisture content to 25-30% and storage of the wet grains in an oxygen limited silo
3. Acid preservation of high moisture grains- The use of acids to preserve high moisture
grains through mixing of 1 to 1.5% propionic acid, mixtures of acetic and propionic or
formic and propionic acids.
ii. Hot processing methods
1.
Steam rolled and steam flaked grains-Grains are subjected to steam for appropriate time
prior to rolling usually just enough to soften the seed.resulting an improved physical texture
2.
Pelleting- Pelleting is accomplished by grinding the feed and then forcing it through a thick
spinning die with the use of rollers, which compress the feed into the holes in the pellet die.
3.
Popping- This is produced by acting of dry heat, causing a sudden expansion that ruptures the
endosperm of the grain. It increases gut and rumen starch utilization.
10.2.2. Roughage processing
1. Baled roughage- Balling is one of the most common methods of handling roughages. It has
an advantage over loose hay by ease of handling, transporting and minimizing losses.
2.
Chopped and ground roughages- Chopping and grinding put roughage in physical form that
can be handled. It tends to provide a more uniform product usually reduces refusal and
waste
3.
Pelleting- Roughages must be ground before pelleting. This appears to result from an increase
in density with more rapid passage through GIT and reduce digestibility. Net nutrient
uptake by animals is increase when consuming pelleted feeds even when the digestibility
is lowered because of the increased consumption.
10.3. Processed feed quality and safety control
59
The objective of quality control of feedstuffs is to insure that the consumer obtain feeds that are
not undesirable, true to their nature and have desired results.
Quality control of row material
Preliminary inspection of row material
1. Colour, odour, texture, density of the material
2. Evidence of wetting
3. Presence of adulteration such as stones, dirt or other foreign materials
4. Storage pestes
5. Evidence of damaged or broken kernels etc
6. Moisture should not be more than 10%(determine moisture of the feed rapidly
Chemical tests
Analyze for proximate principle, this indicates possible constraints on usage due to the presence
of excessive content of crude fiber, fat or total ash.
Toxicological Tests: Some ingredients contain endogenous toxic substances which may at low
concentration adversely affect feed conversion and palatability and at higher concentration, even
result in the death of animals
Finished feed quality: Finished feed assays are necessary because they provide the mill with a
final report on how wills the quality was controlled. Analytical methods are available to detect
the presence of ruminates of ruminant animal protein, other protein meals in animal feeds such as
enzyme-linked immunosorbent assay (ELISA), Feed microscopy and DNA analysis.
Feed storage
 Storage loss: storage loss is measured as reduction in weight. But this loss may be
qualitative as well in terms of nutritional
Factors that affect feed value and deterioration during storage
1. Physical factors: These are moisture of grain, temperature and relative humidity of air, grain
size and shape and storage period
2. Biological factors- these are insects, fungi and rodents,
3. Mechanical factors and chemical factors: Damage to the grains during harvesting,
transportation and mechanical handling and this expose the nutrients and may result in rapid
spoilage during storage:
4. Engineering factor: structure- bag or bulk storage -Design of storage structure:
Factors that influence deterioration change during storage are
Moisture
Oxygen supply
Temperature of stored grain
Condition of product
CH 11. ROLE OF BIOTECHNOLOGY IN ANIMAL NUTRITION
The largest impact of biotechnology on livestock production is increasing the livestock feeds
through improving nutrient content as well as the digestibility of low quality feeds through use of
efficient feed additives.
60
11.1. Biotechnology Products as Feed Additives
A lot of feed additives are being currently used and new concepts are continuously developed
 Silage inoculants
 Supplementation of amino acids
 Removal of anti-nutritional factors and toxins through enzymes
 Enzymes for increased digestibility of nutrients (monogastric and ruminant)
 Enzymes for increased digestibility of non-starch polysaccharides
 Supplementation of endogenous enzymes for improved digestion
 Supplementation of immune products such as disease-specific antibodies
 Supplementation of hormones and prebiotics to promote gut growth and health
 Supplementation of probiotics
 Supplementation of enzymes to reduce nutrient content in waste
 .
11.2. Biotechnology for Fibrous Feeds Improvement
It is well known that some micro-organisms, including cellulose enzymes from anaerobic bacteria
and white rot fungi (Pleurotus ostreatus) can degrade lignin in the cell walls. Several fungal strains
have been used for lignocellulosic hydrolysis such as Asprigullus niger, A. terreus, Fusarium
moniliforme and Chaetomium celluloyticu. However, among many species of fungi white rot fungi
have been reported to be suitable for treatment of roughages so far. The white rot fungi have the
capacity to attack lignin polymers, open aromatic rings and release low molecular weight
fragments
11.3. Biotechnology in Forage Breeding
Genetically engineered forage crops, with a range of potential benefits for production, the
environment and human health, have been developed. Genetically engineered forage crops are
genetically modified using recombinant DNA technology with the objective of introducing or
enhancing a desirable characteristic in the plant or seed. These transgenic forage crops are aimed
at offering a range of benefits to consumers, as well as developers and producers
11.4. Defaunation in Ruminants
Protozoa, unlike bacteria, are not vital for the development and survival of the ruminant host, and
their elimination (defaunation), although producing a less stable rumen environment, has been
found to reduce gaseous carbon and nitrogen losses. It has been established that ruminants can
survive with or without these organisms; however, manipulating their population may affect
protein metabolism in the rumen.
61
4. RANGE ECOLOGY AND MANAGEMENT
Course Description:
The course provides students basic knowledge about rangeland concepts and principles; range
community composition; community pattern in space and in time-succession; gradient analysis;
primary and secondary productivity. Specifically, it deals with rangeland management theories
(equilibrium versus disequilibrium), models and paradigms such as the concept of rangeland
success theory; range condition and trend analyses; plant – animal – and soil interaction, nutrient
cycling in rangelands; range improvement practices including weed and bush encroachment
control, range re-seeding, fertilization, and grazing systems.
Learning Outcomes:
Upon successful completion of this course, students should be able to:

Understand about the distribution and types of rangelands;

Understand about the ecology of rangelands and how it differs from other ecosystems;

Gain knowledge to undertake rangeland inventory and rangeland improvement planning; and

Understand the role of rangelands in wildlife conservation and their interactions.
Definition: Rangeland is a kind of land characterized by native vegetation which is predominantly
grasses and shrubs suitable for grazing/ browsing. It is vegetation consisting of a native species
with a woody plant cover of less than 40% on which management is restricted to grazing, burning
and control of woody plants.
Why do we study this course?
•
Large area/huge resource
•
25-50% of world land surface is rangeland
•
About 60% of the Ethiopian land surface is rangeland
•
Mainstay for pastoral societies throughout the world
•
Centre of biodiversity
•
Expansion of cultivation and tree clearing
•
Increasing deterioration of performance of animals
•
Increasing risk of recurrent drought
62
•
Expansion of aridity
•
Increasing soil erosion and range degradation
•
Multiple-use:
•
Grazing, browsing, nature conservation, dwelling, recreation, water, wildlife,
mining, food, fiber, fuels, pharmaceuticals and medicines etc.
•
Habitat to wild and domestic livestock,
Physical limitations of rangelands
Low and erratic precipitation, rough topography
Poor drainage, and/or cold temperatures
Are unsuited to cultivation
Importance of range resources
1. Forage Production or source of feed
In most developing Africa and South American countries, rangelands provide over 85% of the total
feed needs of domestic ruminants.
2. Production of Animal Products
 Rangelands play a major role in supplying animal products in the world
80% to 90% the food energy consumed by nomadic African herders come from meat,
milk, and blood supplied by their livestock
These animals also serve as a cash crop that can be used to buy other food.
Rangelands had also the most important animal breeds for meat production example the
Borana breed
More than 90% of export live animals and meat is from pastoral and agro-pastoral areas
of Ethiopia
3. Habitat for Wildlife
 Rangelands are the primary habitat for nearly all wild animals highly valued for meat,
hunting and aesthetic viewing.

Rangeland wildlife has potential as a source of meat for human consumption in many
African countries

Most of the endemic wildlife are found in the rangelands
63
4. Water: In some parts of the world, where the human population is rapidly growing but
arid to semi-arid condition prevail; water is becoming the greater importance than forage
as a rangeland product

In the western states, forested and alpine rangelands are the primary source of water
for agriculture, industrial and domestic use.
5. Ecological Role of Rangelands: Provides natural service such as fertility of soils, water
cycling, and biomass production, cycling of nutrients, and control natural pathogens and
parasites.
6. Aesthetic and Ethical Value: They create the pleasant appearance of range environment
 As ethical value, range conservation is the individual responsibility to conserve the
resources for the future

Conservation of game animals

Increase the national income of the country by tourist attraction
Range Ecology Defined:

It is the scientific study of the distribution and abundance of living organisms and how
the distribution and abundance are affected by interactions between the organisms and
their environment.
Range management is applied ecology because it deals with manipulation of organisms and
sometimes their environment with the goal of increasing output usable to man.

The living and nonliving elements comprising a designated piece of rangeland are
referred to as a rangeland ecosystem
Abiotic (Non-living) Components of Ecosystems
•







Climate
Heat (temperature)
Precipitation patterns
Air circulation (wind patterns)
Solar radiation
Light
Atmosphere
Substrate (mostly soils)
64
Biotic (living) components of range ecosystems



Vegetation
Animals
Microbes
Definitions of ‘Range Management’:



It is the management of a renewable resource composed of several range ecosystems for
the optimum combination and sustained yield of products and values
Range management concerns grazing, burning and the control of woody plants on
rangelands
Range management is a discipline and an art that skillfully applies and body of
knowledge accumulated by range science and practical experience for
(1) Protection, improvement, and continued welfare of the basic resources; and
(2) Optimum production of goods and services in combinations needed by society
Range management is based on five basic concepts:
1. Rangeland is renewable resource
2. Energy from the sun can be captured by green plants that can only be harvested by the
grazing animal
3. Rangelands supply humans with food and fiber at very low energy costs compared to
those associated with cultivated lands.
4. Rangeland productivity is determined by the characteristics of the soil, topography, and
climate
5. A variety of “products,” including food, fiber, water, recreation, wildlife, minerals, and
timber, are harvested from rangelands
Reasons for low productivity of rangelands in Ethiopia:





Weed and bush encroachment
Poor soil fertility
Undulated terrain feature
Climate change
Unscientific management
Major rangeland classification of the world
65
Rangeland types are:

Grasslands

Savannas

Shrub lands

Steppes

Desert

Shrub lands

Shrub woodlands

Savanna woodlands

Woodland

Forests
Grassland categorized into:





Dry grassland
Highland grassland (2200- 3000 m.a.s.l)
Mountain grassland (>2500 m.a.s.l)
All types of animals - insects, invertebrates (lower animals) and ungulates are found
Diversity and productivity of grasslands are directly related to rainfall and temperature
Causes of Degradation of Rangelands
– Over grazing and overstocking
– Lack (shortage) of rain fall (pastoral/agro-pastoral areas)
– Tree/bush clearing and use of wood for fire
– Competition of land for cultivation and grazing
– Population pressure
– unscientific management
– Communal system of grazing (common property)
– Decreased mobility of pastoralists=> If they stay more in some localized area for
longer periods of time and Climate changes
Effects of Range Degradation
66

Decreased forage availability in the ranges providing nutrient for herbivores lead to both
(Reduction in grazing and browsing capacity)

Deterioration in body condition of animals

Deterioration in performance of animals

Environmental degradation/loss of range land biodiversity

Reduction in woody and herbaceous biomass,

Replacement of desirable forages with unpalatable plants

Compaction of soil by Livestock

Decreased soil fertility due to loss of plant cover

Decreased absorption of rainfall by soil
Rangeland Biodiversity





The variety of life on Earth, its biological diversity is commonly referred to as
biodiversity.
The number of species of plants, animals, and microorganisms,
The enormous diversity of genes in these species,
The different ecosystems on the planet, such as deserts, rainforests and tundra, savannah,
grasslands etc are all part of a biologically diverse Earth
Appropriate conservation and sustainable development strategies attempt to recognize
this as being integral to any approach
Example: range land management)
Biodiversity Strata
Genetic diversity: the genetic building blocks occurring among individual representatives of a
species. The variation in the information represented by the genes of individual plants and
animals.
Species diversity: the living organisms occurring in a particular site. It is the variety within and
between species, subspecies, and populations.
Ecosystem diversity: the species and ecological processes, both their kind and their number, that
occur in different physical settings.

the variety of communities of plants and animals within particular habitats at scales
ranging from individual habitats to landscapes and bioregions
67
Landscape diversity: the geography of different ecosystems across a large area and the
connections between them
Functional diversity: the range of functions generated by ecosystems, including ecosystem life
support functions, such as regulating water and carbon cycles and photosynthesis
Cultural diversity: How the societies exploit range resources; cultural norms, taboos, rules,
regulations and so on
Why Is Biodiversity Important?



Biodiversity actually boosts ecosystem productivity where each species, no matter how
small, all have an important role to play and that it is this combination that enables the
ecosystem to possess the ability to prevent and recover from a variety of disasters
Biodiversity must then encompass the variety of living organisms, the genetic differences
among them and the ecological processes and landscapes in which they occur.
This is obviously useful for mankind as a larger number of species of plants means more
variety of crops and a larger number of species of animals ensure that the ecosystem is
naturally sustained.
Loss of Biodiversity and Extinctions
It is expected that human activity is causing massive extinctions from various animal and
plant species and the ecosystems.



Climate change has also adverse effect on range biodiversity
The costs associated with deteriorating or vanishing ecosystems will be high
However, sustainable development and consumption would help avert ecological
problems.
Why to conserve biodiversity in rangelands?
Different arguments for the conservation of biodiversity in rangelands are as follows:
A) Ethical and aesthetic arguments:



Apart from ecological and economic arguments based on the notion that biodiversity
should be conserved for reasons of self-interest, ethical and esthetic arguments are also
commonly put forward
Aesthetic arguments say diversity has a value in itself, that organisms are attractive in
their own right
we have an ethical responsibility to preserve biodiversity for future generations
B) Economic arguments:

Economic arguments for biodiversity conservation in rangelands may be said to have
direct and indirect elements;
68






Example, loss of large mammals or indiscriminate burning can result in reduced tourism
revenue
While replacement of some grass species can reduce soil fertility and quality,
contributing less to ecosystem services
Changes in the mix of species modifies the ecosystem over the long term
Low income groups whose livelihoods depend heavily on rangeland production are
particularly affected
Economists argue that some loss of biodiversity is an inevitable and justifiable cost of
economic development
An example of an externality is the cost of salinity arising from vegetation clearance
C) Ecological arguments



Rangeland ecosystems provide ‘natural’ services such as fertility of soils, water cycling,
biomass production, cycling of nutrients, evolution or natural control of pathogenic and
parasitic organisms.
The evidence suggests that various types of interference with the balance of organisms
leads to long-term declines in biodiversity
Seeding a natural grassland with high-input exotics will change the biomass output and
forage value over a short period
Plant Succession and Climax Concepts

Plant succession is a directional non-seasonal cumulative change in the types of plant
species that occupy a given area/range land/ through time.
 Replacement of community by other/orderly process of community changes
 It involves the processes of colonization, establishment, and extinction which act on the
participating plant species.
 Most successions contain a number of stages that can be recognized by the collection of
species that dominate at that point in the succession
 Succession begin when an area is made partially or completely devoid of vegetation
because of a disturbance.
Some common mechanisms of disturbance are:

over grazing/overstocking,

fires and wind storms,

volcanic eruptions,

logging, climate change,

severe flooding, disease, and

pest infestation
69

Succession stops when species composition changes no longer occur with time, and this
community is said to be a climax community/stable equilibrium
Types of Succession
A) Primary succession - is the establishment of plants on land that has not been previously
vegetated




Begins with colonization and establishment of pioneer species.
It usually starts from bare areas and proceed to the development of somewhat stable
climax vegetation
Such changes require extremely long periods, on the scale of hundreds or even thousands
of years
Consequently primary successions may be of interest, but they play a small role in range
management
B) Secondary succession - is the invasion of a habitat by plants on land that was previously
vegetated.
•
Removal of past vegetation may be caused by natural or human disturbances such as
fire, logging, cultivation, destructive grazing;
•
Secondary succession are those that occur following some type of disturbance;
•
Important type of succession concerning to range management;
•
Range managers routinely deal with secondary succession, but rarely with primary
succession;
•
However, sometimes erosion does change the initial soil surface conditions.
•
Generally, in secondary succession we are concerned mainly with vegetation changes and
how these changes influence habitat for other organisms
•
Secondary succession usually occurs much faster than primary succession and generally a
more predictable fashion
•
The variability in secondary succession is reduced as the climax is approached
70
Autogenic succession - is a succession where both the plant community and environment
change, and this change is caused by the activities of the plants over time.
– After the last volcanic eruption.
Progressive succession - is a succession where the community becomes complex and contains
more species and biomass over time.
•
Progressive succession/progression, refers to vegetation changes that lead to more diverse
communities with higher productivity
•
Positive successional tendency
•
Plants succeed toward the climax
Allogenic succession - is caused by a change in environmental conditions which in turn influences
the composition of the plant community.
•
Measurements indicate sedimentation rates of about 1 cm per year on the mud flats that are
found 15 kilometers (9 miles) into the estuary.
•
Over the last 100 years, this salt marsh has increased its elevation and has extended itself
seaward by 800 meters (2600 feet).
Retrogressive succession - is a succession where the community becomes simplistic and
contains fewer species and less biomass over time.
•
•
•
•
Some retrogressive successions are allogenic in nature. For example, the introduction of
grazing animals result in degenerated rangeland
Succession in reverse.
Negative succession
Involves plant community changes away from the climax vegetation.
71
•
It is usually caused by some types of disturbances such as logging, fire, grazing,
cultivation and so forth
Range Inventory and monitoring (evaluation/analysis)
Rangeland inventory: it means the systematic acquisition and analysis of resource information
needed for planning and for management of rangeland
•
Inventory and monitoring activities are essential features of a range management plan
Monitoring: the orderly collection, analysis, and interpretation of resource data to evaluate
progress toward meeting management objectives.
•
•
This process must be conducted over time to determine whether or not management
objectives are being met.
As such inventories serve as baseline data to aid in the development of a range
management plan
The primary purpose of an inventory is to provide an accurate representation of:
•
•
•
•
•
•
•
•
•
Existing condition,
Trend,
Forage production,
Soil characteristics and soil health,
Utilization/grazing use,
Livestock numbers, wild life numbers,
Water resources,
Vegetation types (ex. grasslands, savannah, forests etc),
Range water shed health, precipitation and so on)
Inventories might include such features as:
•
•
•
•
•
•
•
•
•
•
Vegetation type,
Topography,
Soils,
Streams,
sSock water development, fences, and so on
Details of Inventory
Extensive or general/broad
covers large area; ex. National survey
Intensive or details/small area
e.g. grazing potential of a district
Utilization Survey of Rangeland
Varies purposes of grazing surveys in rangeland monitoring are:
72
•
•
•
•
•
•
•
Determining effectiveness of management practices
Determining if forage supply and demand are in balance
Documenting the effect of grazing on natural resources
Documenting the effectiveness of movements towards desired condition
Documenting reasons for range condition
Gaining a better understanding of resources and their management
Using the information gathered to provide for adaptive management strategies
Forage utilization has been defined as percentage of the current year’s herbage production
consumed or destroyed by herbivores.
•
•
Utilization estimates can be used to adjust stocking rate
Direct estimates of utilization have been made using quadrates or paired plots or an
individual plant basis
Qualitative techniques of measuring utilization based primarily on visual appearance:
1.
2.
3.
4.
5.
Unused (0-5%),
Lightly used (6-40%),
Moderately used (41-60%)
Heavily used (61-80%), or
Severely used (81-100%)
They can be rapid and reasonably accurate by well-trained, experienced personnel
•
•
Used for assessment of current grazing pressure
Adjust grazing pressure if excessive utilization
Trend Analysis
•
•
•
•
•
•
•
Direction of change in a range ecological condition or the direction and rate of change in
an attribute as observed overtime
Trend is considered whether the range is improving (upward) or decreasing (downward)
or stable
Used to indicate conditions for livestock grazing as indicated by increasing productivity,
cover, and succession toward climax conditions
Thus, to say whether a trend is upward or downward, one must specify the use or criteria
used.
If the trend is used to correspond to succession stages, upward trend would be toward
climax and downward trend would be away from climax
Trend is a long term effect; at least 5 years data (information is needed to calculate trend
in rangelands)
Enclosure areas (ungrazed areas)/bench mark are an important tool when trend is
measured
73
•
•
•
•
Enclosure areas are necessary to separate climatic influences from those caused by
grazing
If range improvement occurs periods of average or near average precipitation, it is
probably due to grazing management
However, a down ward trend in drought years or an upward trend in above-average years
may be more the result of climatic conditions than that of grazing management
Enclosures (in this case ungrazed areas) can be valuable in separating these influences
Range Condition
Range condition refers to the state of health of the range, OR
(1)The present status of a unit of range in terms of specific values or potentials
(2)The present state of vegetation of a range site in relation to the climax plant community
•
•
•
•
It has historically based on the amount of climax vegetation remaining on the site
Changes in range condition scores overtime are usually the basis for monitoring
management effectiveness
Range condition classification provides an indication of management inputs necessary
If ranges are in good or excellent condition, maintain them in a stable condition may be
the best management strategy
However, if they are in poor or fair condition, management that is aimed at “improvement” may
be indicated. Generally four condition classes are recognized:
•
•
•
•
Excellent
Good
Fair
Poor
Differences between condition classes are sometimes arbitrary since they really form a continuum,
from badly depleted range areas to those with maximum cover and productivity.
Differences in range condition are often indicated by differences in species composition, but range
condition is generally defined as departures from some conceived potential for particular site
It is important to distinguish changes in vegetation overtime on one site from vegetation
differences from site to site at same time
Plant characteristics
Percent climax
74
Soil characteristics

Dense stand of tall, deep
rooted perennial grasses. Few
shrubs and sod grasses
100%-Excellent

Loamy, dark soil, rich in OM.
75%

High moisture content
Short perennial grasses and
forbs. Some shrubs
Good-50%
Loamy to sandy soil. Moderate
moisture
Annual forbs and grasses
Fair-25%
Gravelly loam. Little organic
matter. Little moisture
Low plant forms. Lichens, fungi work
on rocks.
Poor-0%
Little breakdown into coarse rocks
•
Bare rock
Bare rock (dry)
Based on the above table the following ratings will be used to determine range condition:
Range condition
•
•
•
•
Excellent
Good
Fair
Poor
Percent climax
•
•
•
•
76-100
50-75
26-50
0-25
Rangeland health:
•
•
•
The degree to which the integrity of the soil, vegetation, water, air and the ecological
processes of the rangeland ecosystem is balanced and sustained
Originally, species occurring on each site were classified, based on their reaction to
grazing, decreasers, increasers, or invaders.
Decreasers are highly palatable plants that decline in abundance with grazing pressure
Rangeland and Wildlife
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Wild life are a valuable rangeland resources. However, over the past several decades this
resource has been greatly diminished due to the over exploitation and habitat loss.
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Abundance and Diversity
Abundance
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Eastern Africa has long been known for the abundance, uniqueness and diversity of its
wildlife.
And in fact the region does contain, within the savannahs of northern Tanzania, the
world's largest concentration of large mammals.
However, wildlife are not evenly distributed throughout the region but instead vary in
abundance, composition and productivity
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Probably because of competitive interactions between species, the composition of
wildlife communities also varies with habitat.
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For instance, in higher rainfall areas herbivore communities tend to be dominated by very
large species, such as buffalo and elephant, which may contribute up to 75% to total
biomass, whereas in more arid grasslands smaller species, such as wildebeest and zebra
dominate.
Diversity
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Eastern Africa’s high faunal biodiversity reflects the existence of a large number of
species of mammals and other higher vertebrates.
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This in turn reflects a diversity of habitats, created by differing combinations of
elevation, rainfall, soil and surface and ground water.
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Ethiopia and Tanzania are among the top 25 endemic – rich countries of the world in
terms of higher vertebrate species, whereas Kenya, Uganda, Tanzania and Ethiopia are,
individually, among the world leaders in terms of species richness and endemism of
mammal species
Present Situation
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Wildlife populations in eastern Africa have greatly diminished over the past century, both
in amount and distribution
Hunting has been a major factor in reducing wildlife numbers
Wildlife are a valuable rangeland resource.
There are good moral, aesthetic (tourism), economic (production of goods and generation
of revenue) and ecological habitat creation, disease and vermin control etc. are reasons
for conserving wildlife.
Wildlife are important economically primarily because their management provides for the
possibility of increasing income without having to increase animal biomass, which might
place undue pressure on the environment.
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The principal economic uses of wildlife are:
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Tourism, which is possibly the single greatest economic use;
Safari / trophy hunting, which is the most lucrative and easiest to implement;
game cropping, and
Domestication of game species.
Increasingly, local communities are being asked to take responsibility for (and benefit
from), the conservation and management of wildlife.
Although there has been some success in this, doubts exist as to whether such activities
will be able to continue over the long term without outside help
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