Animals Feed

Feed is the material which after ingestion by animals is

capable of digested, absorbed and utilized.

Nutrients; It is a feed components which are capable of

being utilized.

The main components of feed, plants and animals are:

Water

Dry matter

A- Organic B- Inorganic

Carbohydrates Minerals

Lipids

Proteins

Nucleic acids

Organic acids

Vitamins

Metabolism

Metabolism is the name given to the sequence of

biochemical processes that take place in the living

organism.

Water

Water is not normally thought of as a nutrient, but life

could not be sustained without water.

The water content of animal body varies with age.

The newborn animal contain about 75-85% H2O, but this

falls to about 50-60% in adult animal.

Water serves two functions for all animals:

1- As a major component in body metabolism.

2- As a major factor in body temperature control.

Water Functions

Body Metabolism : All the biochemical reactions that

take place in an animal require H2O.

As a Solvent : It is a solvent for a wide variety

compounds, which are ionize readily in water.

As a Transport Medium : In which nutrients are

transported about the body and in which waste

products are excreted.

As a Dilutant : H2O provides for dilution of cell

contents and body fluids .

Hydrolysis and Oxidation : H2O is involved in

Hydrolysis as a substrate and in oxidation as a

product of the reaction.

Water Sources

Drinking water.

Water contained in or on feed.

Metabolic water.

The importance of these different sources differs

among animal species, depending on:

A) Type and composition of diet.

B) Nature and habitat of animal.

C) The ability to conserve body water.

All farm animals require copious amount of water when

producing at a high level, particularly when they are

heat-stressed.

The water content of feedstuffs is very variable.

In forage it may range from a low of 5-7% in straw to as

high as 90% or more in young grass.

Body Temperature Regulation

Water is a high specific heat, high thermal conductivity,

and high latent heat of vaporization allow :

Accumulation of heat.

Ready transfer of heat.

Loss of large amount of heat on vaporization.

These physical properties of water are enhanced by

physiological characteristic of animals.

Water Losses

Loss of H2O from animal body occurs by way of:

Urine

Feces

Insensible water(that lost via vaporization from

lungs, and dissipation through skin).

Sweat (from the sweat glands in the skin).

Water Consumption and Requirement

Water requirement for any species of healthy animals

are difficult to delineate.

This is so because numerous dietary, environmental

factors, and differences in the physiological state affect

water absorption and excretion.

In general, about 2-5 units of water are consumed per

unit of dry feed, but this is affected by:

Animal species.

Type of diet.

High environmental temperatures.

Carbohydrate

It is the major components in plant tissues.

They comprise up to 70% or more of forages DM, and

higher (85%) in some seeds (cereal grains).

Classification

The CHO are usually divided into two major groups:

1- Sugars : The simplest are the monosaccharides.

It is restricted to those CHO containing less than ten

monosaccharides.

2- Non-Sugars : It is divided into two main groups;

Homopolysaccharides: like starch and cellulose.

Heteropolysaccharides: like hemicellulose.

In animal nutrition carbohydrates serve as a source of

Energy for normal life processes.

Glucose is a simple sugar, it involved in energy

transformation and tissue synthesis.

Starch is less soluble forms, serve as energy reserves in

roots, tubers and seeds.

Cellulose and hemicellulose are insoluble fractions.

Preparation for Absorption

Only monosaccharides can be absorbed from the

GI-tract.

Starch, which is occurs in two molecular configuration of

glucose polymers, Amylose and Amylopectin linked via

glucose-1-4-∝ glucoside linkage.

The digestive enzymes secreted by animals are generally

able to hydrolyze both types of starch efficiently.

∝ − Amylase can hydrolyzed the starch to maltose, then

by maltase to glucose.

Microflora of the rumen and caecum produce cellulase,

which is hydrolyzing the glucose𝛽1,4𝑔𝑙𝑢𝑐𝑜𝑠𝑖𝑑𝑒 Linkage

of cellulose to produce glucose and then VFA.

Absorption of Monoccharides

The upper section of SI has the gratest capacity to absorb

monoccharides.

In general, glucose and galactose are absorbed at the

highest rate.

Glucose is transported, against its concentration gradient

by coupling its transport to Na, across cell membranes.

Conversion of some monosaccharides to glucose occurs

within the intestinal mucosal cell.

Fructose is converted to lactic acid by the intestine.

Also found that fructose was absorbed with little

intestinal conversion to glucose.

Sugars apparently share a common pathway of transport

across the intestinal mucosal cell.

The absorption of soluble CHO often exceeds 90%.

The rate of starch digestion in preparation for absorption

is affected by many factors:

Practical size.

Nature of the starch (Amylose and Amylopectin).

Interactions with protein and fat.

Presence of anti-nutrients (Enzyme inhibitors).

Metabolism

The endproducts of CHO digestion;

In non-ruminants animal are glucose and very little of

galactose and fructose.

In ruminants are acetic, propionic and butyric acids with

small amounts of organic acids.

Anabolism : It is a metabolic processes in which complex

compounds are synthesized from simpler substances.

Catabolism : It is the processes involve the degradation

of complex compounds to simpler materials.

Energy, as a result of the various metabolic processes, is

made available for mechanical and chemical work.

Butyric acid is changed, when passes into portal blood

asβ-hydroxybutyric acid(BHBA).

Acetic and propionic acids pass almost unchanged into

the portal blood and are carried, together with BHBA, to

the liver.

Acetic, and BHBA pass from the liver, via the systemic

blood, to various tissues and used as sources of energy

and fatty acids.

Propionic acid is converted to glucose in the liver.

Glucose may be converted partly into:

glycogen and stored.

L-glycerol-3-phosphate and used for triglyceride

synthesis.

Enters the systemic blood and is carried to the

tissues, and used as an energy source.

Glucose as an Energy Source

Glucose is metabolized to give energy in a two-stages:

Glycolysis, can occur under anaerobic condition and

results in pyruvate production.

Pyruvate (under aerobic condition), is oxidized to

CO2 and H2O, with production of energy.

Lipids

Lipids are organic compounds, insoluble in H2O, but

relatively soluble in organic solvents.

It serve important biochemical and physiological

functions in plant and animal tissues.

Lipids Classification

Simple lipids

The store of triglyceride in the body is mobilized to

provide energy by the action of lipase.

This enzyme is catalyse the production of glycerol and

simple lipids are esters of fatty acids (FA) with various

alcohols.

Fats and oils are esters of FA with glycerol, and waxes

are esters of FA with alcohols other than glycerol.

Compound lipids

These are esters of FA containing non-lipid substances

such as phosphorus, carbohydrates and proteins.

They include:

Phospholipids; are fats containing phosphoric acid.

Glycolipids; are fats containing carbohydrate.

Lipoproteins; are lipids bound to proteins .

All are found in blood and other tissues.

Derived Lipids

Include substances derived from simple or compound

lipids by hydrolysis (FA, glycerol and other alcohols).

Sterols

These are lipids with complex phenanthrene-type ring

structures.

Terpenes

These are compounds that usually have isoprene-type

structures.

Glycolipids, lipoproteins, and sterols are very important

in metabolism but are present in the body in much lower

amounts than triglycerides (storage form of energy).

Lipoproteins play a key role in transport via the blood of

Triglycerides, Cholesterol, and Other lipids from one

organ system to another for metabolism.

Wax and terpenes are unimportant and poorly utilized.

In general:

Fat and oils quantitatively make up the largest fraction of

lipids in most food materials and are characterized by:

* High-energy value.

** serve as a source of essential FA(linoleic, linolenic).

*** Function as a carrier of the fat-soluble vitamins

(A,E,D2,D3,K).

Typical fat yields about 9.45 Kcal of heat, compared with

about 4.1kcal for a typical CHO.

Both, fat and oil have the same general structure and

chemical properties but they have different physical

characteristics.

The most important lipid constituents in animal nutrition

include fatty acids, glycerol; mono-, di- and triacylglycerol

(triglycerides), and phospholipids.

Fatty Acids

Fatty acids consist of chains of C atoms ranging from 2 to

24 or more in length, there is a carboxyl group (COOH) on

the end of each chain.

The general structure is R-COOH, where R is a carbon

chain of variable length.

Linoleic acid, for example, a constituent of corn oil and

other plants oils high in pollyunsaturated FA (C18):

CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH

There are two kinds of FA:

Essential FA; Linoleic(C18:2) and linolenic(C18:3)

apparently cannot be synthesized by animal tissues,

or at least not in sufficient amounts, and so must be

supplied in the diet.

Non-essential FA; which is synthesized by animal,

like stearic, butyric, palmitic, and etc.

Glycerol

Glycerol; It is the alcohol component of all triglycerides,

common in animal and plant tissues.

Mono-, Di, and Triglycerides

These are esters of glycerol and FA.

The FA composition of triglycerides is variable.

The same or different FA may be in all three positions.

There are two kind of triglycerides (TAG):

Simple; when one FA occupied all three positions.

Mixed; when 3 different FA occupied all three positions.

The FA composition of TAG in nonruminants tissue

resembles that of the dietary fat; that in ruminant tissues

are variable and contains mostly saturated FA.(?)

The degree of softness of TAG depends on the number of

double bonds (degree of unsaturation) of the constituent

FA and on chain length.

Phospholipids (phosphatides)

On hydrolysis yield FA, phosphoric acid, and glyceroland

a nitrogenous base.

The exact composition varies as to FA composition and in

other ways.

Phospholipids of animal tissues are higher in unsaturated

FA than are TGA of adipose tissue.

Phospholipids are more widely dispersed in body fluids

than are neutral fat and have emulsifying properties that

allow them to serve important function in lipid transport.

Lipids Absorption

Absorption of lipids depends on:

Emulsification and formation of micelles containing

bile salts.

Phospholipids and other lipids.

Hydrolysis by lipase enzymes elaborated into the SI.

Absorption of long-chain FA occurs mostly via the

lymphatic system, whereas short-chain FA may enter the

portal vein.

Absorbed lipids are carried in the blood as chylomicrons

(protein-coated lipid droplets) and as lipoproteins

varying in proportions of lipid and protein (VLDL, LDL,

HDL).

Lipids mobilized from depot storage(adipose tissue) and

those synthesized in body tissues are transported as

lipoproteins.

FA and Triglyceride Metabolism

Synthesis

Liver, mammary gland, and adipose tissue are the major

sites of biosynthesis of FA and TAG.

The liver is the central organ for lipid interconversion and

metabolism.

In ruminants, a major portion of energy absorbed from

the GI-tract for lipid synthesis is in the form VFA.

Acetate is the primary substrate for FA synthesis in

ruminants.

TAG synthesis occurs by FA acyl-CoA reacting with a

monoglyceride to form a diglyceride an thence a

triglyceride.

Body fat deposition in humans and animals is a dynamic

phenomenon, encompassing both:

Anatomical; it is a adipocyte, size and number variable.

Biochemical ; it is a lipogenesis and lipolysis variable.

Catabolism

Adipose tissue, composed primarily of TAG, is in a

dynamic state, with TAG undergoing continuous

synthesis and degradation (lipolysis).

Lipoprotein lipase (LPL) is the major enzyme responsible

for hydrolysis of circulating (blood plasma) TAG in

chylomicrons .

Fatty acids released from hydrolysis of TAG are

transported via the blood to various body tissue to be

used as an oxidative energy source.

Oxidation occurs in the mitochondria of skeletal muscle,

liver, cardiac muscle adipose tissue and other tissues to

yield CO2 and ketones as products.

Ketones are acetone, acetoacetic acid, and

β-hydroxybutyric acid.

Ketones formation (ketogenesis) is a continuous process,

but it may become excessive in certain disorders such as

(diabetes).

Ketones are removed rapidly from the blood by skeletal

muscle and other peripheral tissues and provide a

substantial supply of energy for use by these tissues.

Level of Feeding and Metabolism

The composition of diet and level of feeding are

important factors responsible for controlling body

composition and metabolism of energy.

Meal-fed chickens have been shown to have elevated

plasma cholesterol and their liver incorporate more

acetate into fatty acids than ad libitum-fed.

Ruminants have not been shown to respond to

frequency of feeding changes .

Long-term fasting results first in depletion of liver and

muscle glycogen and then oxidation of tissue lipids to

meet energy requirements.

Increased lipogenesis occurs in liver and to a smaller

extent in adipose tissue after refeeding of fasted animal.

Abnormalities in Lipids Metabolism

This may occur in animals and humans as a result of :

Genetic factors

In response to alterations in the environment.

Hyperlipoproteinemia:

According to genetic makeup results in high levels of

lipoproteins circulating in the blood with high blood lipid

levels.

Hyperlipidemia:

It is a lack in cell surface receptors for LDL in the liver, a

defect that blocks removal of these lipoproteins from the

blood.

In addition, the animal may produce more LDL than

normal.

Fatty Livers:

Normally, fat constitutes about 5% of the liver weight,

but the value may be 30% or more in pathological

conditions.

Fatty liver may arise from high-fat or high-cholesterol

diet; increased liver lipogenesis caused by:

Excessive CHO or certain B vitamins (biotin,

riboflavin, thiamin).

Increased mobilization of lipids from adipose tissue

caused by diabetes mellitus, starvation, increased

output of GH, adrenal corticotrophic hormone

(ACTH),adrenal corticosteroids(ACSH).

Decreased transport of lipids from liver to other

tissue caused by deficiencies of choline, protein or

certain AA (methionine, threonine).

Cellular damage to the liver(necrosis) because of

infections, vitamin E-Se deficiency.

Protein

Proteins are complex organic compounds, essential

constituents of living organism and are the class of

nutrients in highest concentration in muscle tissues.

All cells synthesize proteins for part or all of their life

cycle, and without it life could not exist.

Except in ruminants, P or its constituent AA must be

provided in the diet to allow normal growth and

production.

The percentage of P required in the diet is highest for

young growing animals and declines gradually to

maturity.

Productive functions such as pregnancy and lactation

increase P requirement.

In addition to H2, O2, C protein contain N and some

protein contain S, P, Fe, Z and Cu.

Amino acids are produced when proteins are hydrolyzed

by enzymes, acids or alkalis.

AAs are characterized by having a basic nitrogenous

group (amino group –NH2), and an acidic carboxyl unit

(-COOH).

Proteins are built up from amino acids by means of a

linkage between the ∝-carboxyl and of one AA and the

∝-amino group of another AA.

Proteins vary widely in chemical composition, physical

properties, size, shape, solubility, and biological function.

All proteins are composed of simple units, AA.

Essential AA

About 10 AA are required in the diet of animals because

tissue synthesis is not adequate to meet metabolic need

(Arginine, Lysine, Methionine, Valine).

Non-essential AA

Those are generally not needed in the diet because of

adequate tissue synthesis(Alanine, Cystine, Proline).

Proteins General Classification

A- Globular proteins; soluble in H2O (Albumin), dilute

acids or bases (Globulin) or in alcohol (Prolamine).

B- Fibrous proteins; insoluble in H2O, resistant to

digestive enzymes,(Collagens, Elastins, Keratins).

C- Conjugated proteins; which contain a wide array of

compounds of a non-protein nature, such as:

Protein-Lipid Complex (Lipoprotein):-

An egg yolk is a phospholipid-protein complex.

A very important type of this complex is the

membrane proteins of animal cells, which act as a

permability barrier and transport substances.

Myelin is a lipoprotein abundant in the nervous

system as a sheath around nerve fibers.

Protein-CHO complex (Glycoprotein):-

These complexes arise from the acceptance of

sugars by AA residues in the polypeptide chain.

Mucoproteins; are complex of protein with amino

sugars (glucosamine, Mucous secretions, enzymes).

Glycoprotein; is a complex of protein and high –CHO

content, such as(Ovomucoid),the trypsin inhibitor in

egg white, distinguished by its high-heat stability.

Functions

Proteins perform many different functions in the animal

body.

In addition to their role as structural components, such

as cell membranes, in muscle, and in skin, and hair,

proteins serve important specialized functions in the

body including a rule in:

Metabolism

Protein metabolism will be considered in 2 phases:

Catabolism or degradation

Anabolism or synthesis

Both processes proceed simultaneously in animal tissues.

AAs are the basic unit required in metabolism, normally

are present in the diet as a proteins, that must be

hydrolyzed, then absorbed as AA.

Thus, the conversion of dietary P to tissue P or egg or

milk P, involves the following:

Intact dietary P hydrolysis in GI-tract (Catabolism).

AA in intestinal lumen absorption from GI-tract.

AA in blood synthesis in tissues (Anabolism).

Intact tissue P.

If the diets P have a deficiency or an imbalanced of one

or more of essential AA, the growth failure is observed in

young animals.

Protein in the feces may includes both unabsorbed

dietary N and metabolic (endogenous) fecal N.

Metabolic fecal N arises from normal metabolism of

tissue P and includes:

N from cells sloughed from the intestinal lining

Residues of digestive enzymes

Other substances secreted into the lumen of GI-tract

After absorption, AAs are subjected to further losses

through metabolism in the liver and other tissues.

These losses of N occur in the mammal mainly as urinary

urea N and in birds as uric acid.

AA Absorption

There is very limited transfer of P, polypeptides, or

dipeptides across the intestinal epithelium.

Certain di, and tripeptides are absorbed from the lumen

of the SI of growing non-ruminants, and from rumen and

omasum of ruminants.

Specific peptide transporters are present in the intestine,

suggesting a biological function for absorbed peptides.

The AA moves across the intestinal cell membrane

Absorption of AAs takes place through active transport.

The brush border membrane of the SI contain at least 2

active transport systems:

One for neutral amino acids.

One for basic amino acids.

against a concentration gradient, requiring energy

supplied by cellular metabolism.

AA Synthesis

AA in the digestive tract have 3 main sources:

1- AA deriving from dietary ingestion.

2- AA recycled along with other endogenous N.

3- AA synthesized by microorganism(in rumen & LI).

All three AA sources are available for absorption.

Microorganism in the GI-tract can synthesized all AAs in

the presence of NH3, S, and C source.

Thus, ruminants and herbivorous nonruminants (horse&

rabbit) can derive most of their AA requirement from

microbial AA from inorganic N or NPN.

Nonruminants (pigs and poultry), must rely on dietary

intake of essential AA for survival.

The non-essential AAs and their C skeleton can be

supplied from tissue synthesis.

Many of body tissues can take part to varying degrees in

these synthetic conversions.

AAs Degradation

Microbial digestion can degrade all AAs .

In animals AAs are degraded by cell- and tissue-specific

pathways.

Liver is the principal organ degrading all AAs except

branched-chain AA(BCAA) and glutamine.

Degradation of many AAs also occurs extensively in SI

cells.

AAs degradation in animals occurs by a variety of

enzymatic reactions.

Fate of AAs after Absorption

It can be divided broadly into 3categories:

1- Tissue protein synthesis

2- Synthesis of enzymes, hormones, and other

metabolites.

3- Deamination or transamination and use of C

skeleton for energy.

Protein Synthesis and Degradation

Protein synthesis in animal tissues requires the presence

of nucleic acids.

All living cells contain many different nucleic acids that

play vital roles.

Deoxyribonucleic acid (DNA), a chromosomal

component of cells, it is the blueprint of protein

synthesis.

DNA controls the development of the cell and the

organism by controlling the formation of ribonucleic acid

(RNA).

All types of RNA are involved in the protein synthesis

Protein degradation in muscle tissue is controlled by

cathepsins and Ca-dependent proteinases (calpains).

Deamination

It is a process involve removal of the amino group(NH2)

from the C skeleton of the AA and entrance of NH2 group

into urea (ornithine) cycle.

Transamination

It is involve the transfer of an NH2 group from one AA to

the C skeleton of a keto acid.

AAs available for P synthesis at the tissue level arise

either from absorption from the GI-tract or from

synthesis within the animal tissue by transamination.

The ability of animal tissue to synthesize AA from other

compounds is the basis for their classification as essential

or nonessential.

Energy Metabolism

Energy (E) may be defined as the capacity to do work.

The plants are consumed by animals and the

constituents broken down, releasing energy which is

used by the animal for:

Mechanical work and transport.

Maintenance of the integrity of cell membranes.

Synthesis and for providing heat.

Heat units have been used to represent the various

forms of E involved in metabolism, since all forms are

convertible into heat.

The animal derives E by partial or complex oxidation of

organic molecules, which are absorbed from diet or from

metabolism of tissues, primarily fat or P and from CHO.

Energy transfer from chemical reaction to another occurs

primarily by means of high-E bonds found in compounds

such as ATP (adenosinetriphosphate).

In animal body metabolism a tremendous transfer of E

occurs from one type to another, for example:

From chemical to heat; (oxidation of fat, glucose or AAs).

From chemical to mechanical; (any muscular activity).

From chemical to electrical; (glucose oxidation to

electrical activity of brain).

Chemical E may be measured in terms of heat and

expressed as calories (cal).

Calorie is defined as the amount of heat required to raise

the temperature of 1 gm of H2O from 14.5 to 15.5°𝐶.

Gross Energy (GE)

It is the quantity of heat resulting from the complete

oxidation (heat of combustion) of feed or nutrients.

Energy values of different feedstuffs or nutrients may

vary, but typical values are:

CHO = 4.10 Kcal/g

Proteins = 5.65 Kcal/g

Fats = 9.45 Kcal/g

The chemical E varies inversely with the C:H ratio and the

O and N content.

Fat contain about 2.5 times as much energy as CHO, this

is reflecting the larger ratio of C and H to O in the former.

Digestible Energy (DE)

There are losses of food E occurring during digestion and

metabolism.

The largest loss is that of E contained in feces.

DE is determined by carrying out a digestion trail, then

determined the E content in feed and feces.

The apparent digested E of feed is the intake of food E

(IE) minus E lost in feces.

DE = IE − FE

This is depending on animal species and diet.

Total Digestible Nutrients (TDN)

TDN is the total of DP and CHO (NFE&CF) plus 2.25 times

DEE(crude fat).

Fat is multiplied by 2.25 in an attempt to account for its

higher caloric value compare with CHO.

TDN = DCP + DNFE + DCF+ 2.25 (DEE)

Metabolizable Energy (ME)

It is defined as GE of feed intake (IE) minus E lost in feces

(FE), urine (UE), and combustible gases(in ruminants).

In ruminants

Combustible gases are made up primarily of CH4.

Low-quality diets result in larger proportion of CH4.

Generally, the percentage of GE lost as CH4 declines as

feed intake increases.

Usual values cited are about 8% of IE lost as CH4 at

maintenance level.

The E of urine is present in N-containing substance such

as urea, hippuric acid, creatinine and non-N compounds

such as citric acid and glucuronate.

On average, about 20% of DE is excreted in urine and

CH4.

ME = DE X 0.80

Factors Affecting ME

1- Apparent Digestibility of the diet.

2- Species of animal.

3- According to whether the AAs in diet are retained for

P synthesis,or are deaminated to urea and excreted.

4- Preparation of diet.

5- Level of feeding.

Heat Increment

Animals are continuously producing heat and losing it to

their surroundings, either directly by radition,conduction

and convection, or indirectly by evaporation of H2O.

The main cause of heat increment is the energetic

inefficiency of the reaction by which absorbed nutrients

are metabolized.

For example; if glucose is oxidized in the formation of

ATP, the efficiency of free E capture is only about 0.69,

and 0.31 being lost as heat.

A further part of the HI is attributable to the processes of

digestion.

In ruminants, some heat arises from the activity of

microorganism in GI-tract; this is known as heat of

fermentation (about 5-10% of GE).

Net Energy (NE)

It is an available E to the animal for useful purposes.

It is used for maintenance and for various form of

production.

Maintenance and repair o

The portion used for maintenance is used for:

Muscular workf tissues

Maintenance of stable body temperature

Other body functions

Most of it will leave the animal body as heat.

Most of it will leave the animal body as heat.

The portion used for productive purposes may be

recovered as:

Chemical E in the tissues.

In some products such as milk, egg, or it may be used

to perform work.