Digestion

The process of breaking down feeds so the body can use them

Four steps in digestion

1. Obtaining food and taking into the body

2. Breaking food down3. Absorbing nutrients4. Elimination of undigested

wastes

Obtaining Food

Animals use their SENSES to find FOOD.

Food is taken in through the MOUTH. This is called INGESTION.

Amount of Food Ingested is determined by:

Hunger -- the intrinsic desire for food, regardless of food type or preference

Appetite -- the specific type of food that is preferentially sought.

What Animals Eat

Herbivore -- majority of diet comes from plant products Examples -- Cow, Sheep, Goat, Horse, Rabbit

Carnivore -- majority of diet comes from animal products Examples -- Dog

Omnivore -- eats both plant and animal products Examples -- Humans, Pigs, Poultry, Mouse

Breaking Food Down

Food is broken down in two ways:

1. CHEMICAL -- the use of chemical substances (ENZYMES) to dissolve the food.

2. MECHANICAL -- the use of PHYSICAL structures (chewing, grinding) to break the food apart.

Food is broken down in the following structures:

Mouth -- MASTICATION -- grinding or chewing of food

SALIVA--watery liquid in mouth that begins dissolving the food.

Mastication -- Teeth

Incisors -- cutting and food intake action 55 psi

Canines -- ripping and biting (Carnivores and Omnivores only)

Premolars -- grinding actionMolars -- grinding action

200 psi

Esophagus

the muscular tube connecting the MOUTH with the STOMACH

PERISTALSIS -- the movement of food through the digestive system by a series of muscular contractions Analward Peristaltic Movements

Stomach

Compartment used for digestion and storage

Cattle and sheep (RUMINANTS) have 4 compartments

Horses and swine (NONRUMINANTS) have 1 compartment

Absorbing Nutrients

Nutrients leave the digestive tract and enter the blood so they can be used by every cell

Small Intestine

most of the food nutrients are absorbed into the blood here

The small intestine is very LONG and contains many small folds called VILLI which increase the surface area for more absorption.

Three parts Duodenum, Jejunum, Illeum

Large Intestine

Water is absorbed into the blood and undigested wastes prepare to leave the body

Removal of Undigested Wastes

Not all of the food eaten can be digested and absorbed.

After most of the water is absorbed, waste is removed from the body through the anus or vent.

Other organs that assist in digestion

liver -- stores carbohydrates (glycogen), detoxifies blood,

produces bilepancreas -- produces insulin and

pancreatic juicegall bladder -- stores bile until it is

needed

Terminology of feed as it moves through the system

Feed or FeedstuffIngestaCudChymeDigestive End Products (DEP’s)Fecal Material or Non-Digested End

ProductsFeces

The GI tract -- Descending

Oral cavity (mouth)IncisorsMolarsEsophagusStomach

1 compartment, or 4 compartments

Small Intestine Duodenum Jejunum Illeum

CecumLarge Intestine

(Colon)

RectumAnus

Chemical Digestion

The body produces chemicals (Enzymes) that help dissolve feed.

Refer to chart.

Ruminant Digestive Systems(Polygastric)

Cattle and sheep have a Ruminant digestive systems. This means that their stomachs have four compartments. The first of these compartments contains bacteria that help break down roughage.

Cellulose- a substance found in the cell walls of plants. It cannot be used unless it is first soaked (fermented) by microorganisms.

Two Types of Microorganisms: Bacteria and Protozoa are one-celled

animals. Muscles in the rumen and reticulum help break the food into smaller particles.

Regurgitation

Ruminants consume large amounts of roughages. It is first chewed just enough to swallow it. After they consume the food, they regurgitate it, or force it back into the mouth, so that it can be chewed again. (Chewing Cud).

4 Parts of the Ruminant Stomach

Ruman- the largest compartment; stores and ferments the feed.

Reticulum- foreign particles (nails, wire) are removed (cow magnets)

Omasum- eliminates water from the feed

Abomasum- (true stomach)- gastric juice is secreted; feed is broken down

Monogastic Digestive System

Swine, dogs, bears, and humans have only one stomach. It is difficult for these animals to digest roughages.

Modified Monogastric System

Horses and rabbits have only one stomach, but have structures that contain microorganisms so they can digest roughages. Microorganisms are found in the Cecum.

Avian Digestive System

Birds (Turkeys, Chickens and Pigeons) have crops not found in other species that allow them to digest whole seeds and other hard foods. Crop- food storage Gizzard- feed particles are crushed and

mixed with digestive juices Cloaca- an enlarged part found where the

large intestine joins the vent.

Poultry Digestive System