The document discusses the digestive tract and its functions in animals. It begins by outlining the common functions of the digestive tract, which include intake of food, digestion, absorption, and excretion. It then describes the major sections of the digestive tract in various animals like poultry, ruminants, and nonruminants. In ruminants, the stomach is a multi-compartment organ consisting of the rumen, reticulum, omasum, and abomasum. The small intestine is divided into duodenum, jejunum, and ileum. Associated glands that aid digestion include the salivary glands, liver, gallbladder, and pancreas.

1. 1
ANIMAL NUTRITION-final
DIGESTIVE TRACT AND ITS FUNCTIONS
The common functions of the digestive tract are the intake of food, its digestion and absorption and excretion of
unabsorbed dietary components and waste material. Digestion is the prepration of food for absortion, i.e. reduction of food
particles in size and solubility by mechnical and chemical means. The digestive tract or alimentary tract is the passage
from the mouth to the anus through which feed passes following consumption as it is subjected to various digestive
processes. It consists of the following.
A. Mouth and Pharynx
B. Oesophagus
C. Stomach
D. Small intestine
E. Large intestine
F. Anus
In poultry the true stomach (Figure 1) is proventriculus.
In ruminants, stomach (Figure 2) is a multiple compartment structure consisting of the following:
a. Rumen or paunch
b. Reticulum or honeycomb or water bag.
c. Omasum or manyplies
d. Abomasum or true stomach
Small intestine which is divided into three sections.
1. Duodenum-----upper section.
2. Jejunum---middle section
3. Ileum---lower section.
Large intestine:
1. Caecum
2. Colon
3. Rectum
Associate glands and organs, including:
1. Salivary glands
2. Liver
3. Gall bladder
4. Pancreas

2. 2

3. 3
1. Nutrient digestion:
The processes involved in the conversion of various feed nutrients into forms (called end products) which can be
absorbed from the digestive tract. Most of these processes are accomplished through the action of various enzymes which
are found in the different digestive juices secreted into the digestive tract.
A. End products of digestion:
All nutrients must be converted in order to be absorbed from the digestive tract.
Nutrient End Product
Protein Amino acids
Starch Glucose
Sucrose Glucose and fructose (fructose converted to glucose upon absorption).
Lactose Glucose and galactose (galactose converted to glucose upon absorption.
Cellulose Organic acids and salts of organic acids
Fats Primarily fatty acids and glycerol; some soap.
Minerals Any soluble form
Vitamins Any soluble form
B. Digestive juices
Fluid materials secreted into the digestive tract by glands or tissues along the digestive tract.
Those usually considered are:
1. Saliva 4. Pancreatic Juice
2. Gastric juice 5. Intestinal Juice
3. Bile
C. Enzymes.
Enzymes are organic catalysts. Most are protein in make up. They are usually specific with respect to substrate
and medium requirements. Most enzyme names end in “ase”. A few early named enzymes end in “in”(ptyalin). Today,
enzymes are usually named according to the substrate on which they act, and possibly the action which they affect, with
an “ase” ending. The enzymes usually recognized in connection with carbohydrates, fat and protein digestion are 1)
Amylotytic 2) Lipolytic 3) Proteolytic respectively.
II. Nutrient absorption.
The movement of the end products of digestion from the digestive tract into the blood and /or lymph system is
accomplished by the process of osmosis through the semi-permeable membranes which line much of the digestive tract. In
nonruminants most nutrient absorption takes place in the small and large intestines. The villi of small in intestine
especially facilitate absorption at this location. A large amount of absorption also takes place through the rumen wall in
ruminants. All of the end product of digestion, except those of fat digestion and possibly the fat soluble vitamins, are
absorbed directly into the blood stream.
The end products of fat digestion are absorbed into the lymph system through the lacteals of the villi in the form
of chyle. The latter subsequently enters the blood through the thoracic duct and undergoes certain metabolic changes in
the liver before being used in the tissues.
III. Nutrient transport
The nutrient transport is the movement of nutrients from the point of absorption to the point of utilization. Te
blood is the primary basis for the transport of nutrients and other materials in the animal’s body. However, the lymph
serves as the final link between the blood capillaries and the individual cells. All nutrients are transported in solution in
the water soluble form. The various nutrients are absorbed from the lymph into the individual cells again by the process of
osmosis.
IV. Digestion and Absorption of Nutrients in Animals
Farm animals are classified according to the nature of their digestive tract into two general categories:
A. Ruminants
These are animals such as the cow, buffalo, camel, sheep and goat which ruminate or in other words, chew a cud.
An animal’s cud consists of boluses of feed eaten earlier. Ruminants have a multi-compartment stomach. By means of the
microbial fermentation process of the rumen, such animals are able to make effective use of high fibre feeds and as a
result are frequently fed rations containing high levels of fibrous feeds.

4. 4
Rumen Microbes
Three types of microbes are present in the rumen, bacteria, protozoa and fungi.
Bacteria
Number of bacteria in the rumen is 1010
- 1011
cells/gm of rumen contents. Bacteria are classified on the basis of
their shape as cocci, rods or spiralla. However, classification of bacteria on the basis of substrate they attack in the rumen
is as under:
 Cellulolytic
 Hemi-cellulolytic
 Pectinolytic
 Amylolytic
 Ureolytic
 Methane-producing
 Sugar utilizing
 Acid producing
 Proteolytic
 Ammonia producing
 Lipid-utilizing species
Rumen Protozoa
Number of protozoa in the rumen is 105
- 106
cells/ml of rumen contents. Size of protozoa ranges from 20-200 µm so can
be seen with naked eye. They may form 2% of rumen contents and may contribute 40% of total microbial N. Mass of
protozoa may be equal to the mass of bacteria in the rumen.

5. 5
FEEDING STANDARDS
Feeding standards and nutritional allowances are tables, showing the amounts of food and specific nutrients which
should be provided to different species for various purposes such as growth, fattening, reproduction, lactation, or
strenuous exercise. They serve as guides in feeding animals and in estimating the adequacy of feed intakes and of feed
supplies for groups of animals or people.
Salient features ofdifferent feeding standards
Type of Feeding
Standard
Year Salient features
1. Bohimia 1725 Mentionedcomparison ofhay. His opinion is associatedwith Thaer.
2. Einhof
1808
Efforts to determine nutritive value of feeds treated with water, dilute
acids andalkali, alcohol were made. He isolated the fiber from straw,
barley, Lentils and Bean.
3. Albrecht Taer (Concept of hayequivalence
on extractionof feedmaterial with water
andother solvent was given)
1810
100 Ibs of medowhay = 91 Ibs dry berseem = 200 Ibs of potato. Medow
hay was used as unit for comparisonwith noinformationof chemical
value of feeds.
4. Scandinavian (common grainlike maize,
where/barley were usedas a unit of
comparison).
1984
One feedunit for 150Ibs of body weight andadditional 1 unit for every
3 Ibs of milk. 100Ibs of body wt. requires 0.65Ibs crude protein (CP)
andadd 0.05 Ibs CP for oneIb. of milkproduction.
5. Gruven’s
(Total amount ofproteins, CHO , fats
measuredby analysis).
1859
Cow of 100 Ibs body wt. needs dry matter (DM) 28.7, crude protein2.67,
crude fibre 0.86 & crude carbo. 14.55Ibs.
6. Wolff’s
(Ratio of dig. Protein,carbo.Measuredas
“Albuminoidratio”i.e. Nutritive ratio).
1864
Cow of 1000 Ibs body weight needs DM. 24.5, Digestible crude protein
(DCP) 2.5, Digestible crude fiber (CF) 0.4andDig. Carbohydrates 12.5
Ibs.
7. Kuhn’s
1867
Separate requirement forgrowthmaintenance,productionandwork were
given.
8. Julius Kubus
1887
Based DM of rationneededformaintenance,production and work were
given.
9. Wolff’s Lehmann (Based1896 onmilk
prod. Andfat per-centage ofmilk) 1896
A cow for 1000 Ibs body wt. requires DM. 18, DCP. 0.7, CF. 0.1,
carbohydrate.8 Ibs. For maintenance purpose; but for maintenance +
productionneeds DM. 25, DCP. 1.6, CF. 0.3andcarbohydrates. 10 Ibs.
10. Haecker’s (Basedon milk 1903 prod. And
fat percent of milk.
1903
A cow of 900 Ibs requires DCP. 0.7, CF. 0.1, carbohydrate. 10 Ibs.
11. Kellner’s
1907
Based on starch equivalent,1 IbDCP. 0.63, Dig. Carbo. 6.3, Fat. 0.09
andTDN. 7.132formaintenance and for production of milk, 4% Dig.
Carbo and 0.314 TDN are required.
12. Savage (Suggestedmodifications in
Haecker’s)
1912
1000 Ibs of body weight needs. 0.7 Ibs DCP and 7.925 Ibs TDN.
13. Armsby 1917 Based on Dig. True Protein and net energy value.
14. Morrison (Basedon size of animal. Also
includedCa, P, CaroteneandVit. D.
Requirement.
1915
Publishedfeedingstandards in his book entitled“Feeds and Feeding” 1st
Ed.
1936
1956
1945
Revised feeding standards.
Revised feeding standards.
Requirements of Nutrients were based on modified Morrison’s feeding
standard on DCP and TDN.
15. NRC
(Basedon size of animal. Also include Ca,
P, caroteneandVit. D. requirement.
1970
Revised feeding standard.
16. Agric. Res. Council (ARC) 1965-67 Based on starch equivalent and net energy values.

6. 6
Common Feeds and Their Classification