KEY
Note Taking Guide
Topic # 3045
Digestion Process
Created by: Tracey Hoffman
Resources:
Animal Science Biology & Technology. Interstate Publishers textbook.
I.
Introduction
“The process of digestion reduces feed particle size and simplifies chemical
composition of the feed for absorption by the animal. After absorption , the bloodstream
transports the digested nutrients to body cells.
Rumen: unique stomach chamber that contains multitudes of bacteria that digest
some feedstuffs
Cattle and sheep have a rumen that digests some feedstuffs that other animals,
such as swine and poultry, cannot digest." Pg. 47
II.
ESSENTIAL NUTRIENTS
Water
1. most abundant
2. 40 -80% of total body weight is comprised of water
3. medium for chemical reactions in body
4. major component of bodily fluids
Protein
1. promotes growth and repair of body cells
2. consists of strings of building blocks called amino acids
Amino Acids: building blocks containing nitrogen
3. amino acids cannot be manufactured by the body, but must be consumed in the
feed
4. a deficiency in one or more essential amino acids can cause reduced growth
rate or death
5. plant feeds with high levels of protein
* soybean meal
* young alfalfa hay
* distillers dried grains
6. animal protein feeds
* fish meal
* meat meal
* milk products
Ruminants: animals with a four-part stomach
7. ruminants have the ability to manufacture new proteins
8. during digestion proteins are disassembled into individual amino acids
Carbohydrates
Simple carbohydrates: starch and sugar used as quick energy
Complex carbohydrates: cellulose and hemicellulose cannot be digested by
simple-stomached animals but can be digested by ruminants and horses.
Fats
1. concentrated energy source
2. used to boost energy levels in feeds without increasing the feed volume
Vitamins
1. two classes of vitamins
* fat-soluble
Vitamin A: eye sight and maintenance of skin cells
Vitamin D: bone and tooth development
Vitamin E: red blood cell structure and keys energy metabolism
Vitamin K: essential blood clotting factor
* water-soluble: cannot be stored within the body and must be consumed
or manufactured on a regular basis
2. vitamin needs are met by feeding vitamin-mineral premixes
Minerals
1. two groups of minerals
Macrominerals: major mineral needed in the diet in relatively large amounts
* salt and potassium are involved in maintaining fluid balance in the cells
* calcium, phosphorus, and magnesium are important in bone structure
and development
Microminerals: trace minerals required in smaller amounts
2. macrominerals are usually present in normally fed grains and forages
III.
THE DIGESTION PROCESS
Peristalsis: smooth muscle contractions
Hydrochloric acid: extremely acidic substance that breaks down proteins into
shorter chains of amino acids
Chyme: partially digested material
Peptidases: enzymes produced by the pancreas, which further reduce the amino
acids
Villi: microscopic finger-like projections that increase surface area
Cecum: supports the population of digestive bacteria in horses
Steps in digestion
1. teeth break apart food particles
2. enzymes in saliva begin to break simple carbohydrates
3. food moves down esophagus into the stomach
4. acid in the stomach kills the bacteria ingested with the feed & begins to break
down proteins
5. chyme moves into small intestine (duodenum, jejunum, and ileum)
6. remaining digestive activity takes place in duodenum where peptidases are
mixed with chyme
7. villi absorb digested food particles
8. indigestible components and water enter the large intestine (colon)
9. the colon absorbs water into the bloodstream and undigested material is
packaged for excretion
IV.
TYPES OF DIGESTIVE SYSTEMS
Swine
Monogastrics: one- or simple-stomached
1. designed to use high energy feeds
2. not suited to be fed large amounts of forages, such as hay
3. human and swine digestive systems are similar
Poultry
1. monogastric
Crop: located at the base of the neck, serves as a storage area for ingested feed
Proventriculus: true stomach
Gizzard: structure used to grind feed
Ruminants
1. adapted to diets containing large amounts of forages
2. Examples of forages:
* hay
* pasture grasses
*legumes
* silage
3. ruminants can digest complex carbohydrates
4. four-compartment stomach
Reticulorumen: rumen and reticulum
Reticulum: small pouch located on the side of the rumen and functions as a trap
for foreign materials
Omasum: absorbs water from the chyme
Abomasum: “true-stomach”, contains high levels of acid
5. forage is stored in the reticulorumen
Rumination: forage is regurgitated, chewed, and reswallowed and serves to
reduce particle size
6. forage must be present in the diet to ensure proper rumen function
7. products of digestion or fermentation are called volatile fatty acids or VFAs,
which are an energy source
8. dead bacteria provide the ruminant with large amounts of high quality protein
Symbiotic: relationships between two species that are mutually beneficial
Horses
1. adapted to high forage diets
2. cecum ferments forages
3. VFAs are absorbed by the cecum but microbial protein is lost in the feces