livestock nutrition

Livestock NutritionCh. 2 Digestion in Animals

Objectives 1- Describe the nonruminant

(monogastric), ruminant, and avian digestive systems.

2- Describe the process of digestion in animals.

3- Describe the absorption of nutrients in animals.

Digestive Systems Digestion is a process

that breaks feed down into simple substances that can be absorbed by the body.

This usually involves mechanical, chemical and enzymes.

The compounds are then absorbed into the blood stream.

Digestive tract Also known as the gastrointestinal

tract or the alimentary tract. Begins at the mouth and ends at the

anus.

Three kinds of digestive systems. Non-ruminant (monogastric). Ruminant (polygastric). Avian

Non-ruminant digestive systems. Swine, horses & humans. Single compartment stomach. Includes, mouth, teeth, tongue,

salivary glands, esophagus, stomach, small intestine, liver, pancreas, cecum, large intestine, rectum and anus.

Parts of Swine Digestive Tract Parts of the

swine digestive system.

Know location and function of each part.

Parts of Horse Digestive System Know the location

and function of each part.

Pay particular attention to the highly adapted cecum.

Mouth, part of digestive system. The mouth contains the teeth, tongue,

and salivary glands. Chewing action (mechanical part of

digestion). Food is cut and torn in the mouth, then

mixed with saliva, which is produced in three different places.

Three paired sets of salivary glands, located under the lower jaw and under the ears.

Mouth Saliva contains water, mucin,

bicarbonate salts and enzymes. Horse saliva does not contain

enzymes. In swine, saliva contains the

enzymes salivary amylase and salivary maltase.

Enzymes Enzymes work in the whole digestive

process, form mouth to anus. Enzymes are organic catalysts that cause

and/or speed up digestive action. However, enzymes remain unchanged in

this process. A weak acid solution will halt enzyme

action.

Digestion in the Mouth Saliva stimulates the taste nerves. Water moistens the feed for chewing

and swallowing. Mucin lubricates the feed for

swallowing. Bicarbonate salts buffer the pH in

the stomach.

The Tongue The tongue gathers feed in the

mouth. Directs the feed in the throat for

swallowing. Mixes feed.

Esophagus A tube like passage which leads from

the mouth to the stomach. Peristaltic waves send feed down the

esophagus, (muscle contractions). The cardia, located at the end of the

esophagus prevents feed in the stomach from coming back into the esophagus. ( non-ruminants)

Stomach Pear shaped, muscular organ, receives

feed, where it is further broken down by muscle in the stomach wall.

Gastric juices, secreted by the glands in the stomach wall, start to flow the moment masticated feed enter the stomach.

Gastric juices have about 0.2 to 0.5 percent HCl.

Stomach The wall of the stomach is lined with

muscle, this muscle churns and squeezes the feed.

This action forces the liquid portion on into the small intestine.

The stomach of the horse has less muscular activity than that of other species, causing an increased tendency toward digestive disorders.

Horse Stomach The stomach of a horse is smaller,

compared to other species, in relation to the size of the animal.

Therefore, it is more desirable to feed horses in smaller amounts at one time but provide more frequent feedings.

Small Intestine Duodenum, the first part of the small

intestine. This is where secretions from the

pancreas, liver and intestinal walls occur. Active digestion takes place here. Bile, secreted in the liver is stored in the

gallbladder where it is secreted into the duodenum.

Horses do not have a gallbladder, therefore, bile is secreted continuously from the liver to the duodenum.

Small Intestine The middle part of the Small

Intestine is called the Jejunum. The last part of the small intestine is

called the ileum. Nutrient absorption occurs in these

two section of the small intestine.

Small Intestine Chyme is partially digested feed in the

stomach. Chyme is an acid, semi fluid, gray, pulpy

mass. Pancreatic juice is secreted by the

pancreas, a small gland located between the folds of the small intestine.

Pancreatic juice contains enzymes.

Small Intestine, Proteins Proteins are further broken down into

polypeptides oligopeptides, dipeptides and amino acids, eventually broken down into simple amino acids.

Starch is changed to maltose. Fats in the feed are broken down into fatty

acids glycerol and monoglycerides. Bile helps emulsify fats.

Large Intestine in Swine The small intestine does the majority

of absorption. Cecum in swine has little or no

function. The cecum is the first part of the

large intestine. The colon is the middle and largest

part of the large intestine.

Large Intestine, Horses Cecum is an important organ in horses. The large intestine makes up

approximately 60% of the total digestive tract.

Divided into cecum, large colon, small colon and rectum.

Horses can use large amounts of roughage because of the presence of bacteria in the cecum and colon.

These bacteria digest hemicelluloses and cellulose and ferment carbohydrates.

Large Intestine, Horses IMPORTANT- because the large

intestine of the horse usually contains substantial quantities of ingested material, impaction occurs easily.

This impaction is the start of what horse ailment?

Large Intestine In all species, undigested, unabsorbed

and indigestible material passes from the small intestine to the large.

The main function of the L intestine is to absorb water from the material passing through.

In the Horse, the small colon is the site of most of the water resorption.

Feces, material that is not absorbed or digested.

Anus, the external opening at the end of the digestive tract.

Ruminant Digestive SystemMouth Saliva of ruminants does not contain

enzymes to help digest the starches. It contains buffers which neutralize the

fatty acid produced in the rumen. The rumen contents are maintained at

approximately a pH of 6-6.5. This pH level promotes microbial growth

in the rumen. Mature cows produce about 12 gallons of

saliva per day while sheep produce 2 gal.

Ruminant Digestion Stomach. The stomach of the ruminant contains

four compartments: the rumen, reticulum, omasum and the abomasum.

The rumen or paunch is the first. The reticulum or honey comb is second. There is not a clear partition between

these two compartments. The cardia, (lower part of the esophagus

is common to both compartments. No enzymes are secreted in these tow

parts.

Ruminant Digestion Stomach The third compartment is the omasum or

many plies. It constitutes 8% of the stomach. The omasum contains strong muscles in

the walls. The fourth and last part of the ruminant

stomach is the abomasum or true stomach.

The Abomasum makes up 7% of the stomach.

Ruminant Digestion Ruminants eat rapidly swallowing

much of their feed without chewing. Solid feed goes to the rumen. The liquid part also goes into the

rumen. But passes quickly to the reticulum, then through the omasum and on into the abomasum.

Esophageal Groove These two muscular folds for a passage

way from the cardia, ( the end of the esophagus), to the omasum.

When closed this passage way directs feed from the esophagus directly to the omasum and when it is open the material goes into the rumen and the reticulum.

Its major function appears to be to allow milk ingest by a nursing animal to bypass fermentation in the rumen. Serves no purpose in adult ruminants.

Bovine Digestive system Identify

location and function of each of the parts of the Bovine digestive system.

Rumination After the ruminant animal has filled the

rumen with feed it lies down to ruminate, (chew its cud).

Cattle spend from 5-7 hours ruminating, broken up into 6-8 rumination periods.

Regurgitation is the process of forcing the feed back into the mouth for chewing.

This is done through series of muscular contractions and pressure in the rumen and reticulum.

Rumination The animal breathes in with a closed

glottis. This causes a drop in pressure in the

thorax and esophagus. The pressure in the rumen is now greater,

forcing the cud into the esophagus where it is carried to the mouth, with muscular contractions.

More saliva is then mixed with the feed and it passes into the reticulum, if sufficient chewing has been done.

Rumen Microorganisms Rumen and reticulum contain millions of

microorganisms called bacteria and protozoa.

Together, these tiny organisms feed on the fibrous material in the rumen.

They digest cellulose and compiles starch, synthesize protein and synthesize vitamins.

Microorganisms The three types of rumen bacteria are

streptococci, lactobacilli and celluloytic bacteria.

50-65% of the starch is digested in the rumen.

Protein in the rumen is converted to ammonia, organic acids and amino acids.

Most amino acids synthesized by the rumen, therefore, it is not necessary to supply large quantities of amino acids in the ration.

Functions of the Rumen There is continual flow of feed materials

into and out of the rumen. It acts like a large fermentation vat and

account for about 50-85% of the total utilization of the digestible dry matter in the ration.

Saliva which is mixed with feed helps control the pH of the rumen.

A shift of microorganisms can result from the types of feed fed.

Function of the Rumen Feed material stays in the rumen and

reticulum area from about two hours to several days.

The kind of feed influences time. Concentrates pass quicker than roughages.

Papillae line the interior wall of the rumen, they increase surface area therefore increasing the absorption ability of the rumen wall.

Function of the Rumen Bacterial action in the rumen produces

large quantities (30-50 quarts per hour) of gas, mainly CO2 and CH4.

This gas must be removed or the animal will bloat.

The gas is released through eructation, (belching).

Small amounts are absorbed by the bloodstream and then eliminated through the lungs.

Function of the Reticulum Contains the same bacteria and protozoa

as the rumen. Lined with intersecting ridges that form

honeycomblike projections. Hardware that is ingest are trapped in this

area and generally do not move further through the digestive system.

Feed is moved back and forth between the rumen and reticulum by regular contractions originating in the reticulum.

Function of the Omasum The omasum grinds and squeezes

the feed. Little or no digestive action. The material leaving the omasum is

60-70 percent drier than the material entering it.

Function of the Abomasum Digestion here is much the same as it is in

a monogastric animal. Digestive juices are added to the feed and

it is moistened. There is little or no digestion of fat,

cellulose or starch. pH level of 3.5-4.0. The feed becomes highly fluid as it passes

into the small intestine.

Avian Digestive Systems Different from nonruminant and ruminant. Feed in proventriculus are secreted by the

glandular stomach and mixed with feed. The feed next moves to the gizzard.

Epithelium breaks the feed into smaller particles, further mixing of proventricular digestive juices with the feed in the gizzard.The end of the digestive system is the vent.

Absorption of Nutrients Absorption is the process of taking

nutrients from the digested feed into the blood and lymph systems.

In nonruminants most absorption takes place from the small intestine with a lesser amount being absorbed from the large intestine.

In ruminants there is some absorption of nutrients through the wall of the rumen.

Absorption of Nutrients Villi are small cone-shaped projection on

the wall of the small intestine. Each villi contains a network of blood capillaries through which nutrients enter the blood stream.

Protein is converted to amino acids. Starches and sugars are converted to

glucose, fructose and galactose. Crude fiber is converted to short chained

fatty acids or glucose by digestion. These nutrients pass into the blood

capillaries by osmosis through the semi permeable membranes.

Absorption of Nutrients The two methods of absorption are

diffusion and active transport. Diffusion is the movement of molecules

from an area of high concentration to one of low concentration.

Active transport is the movement of molecules from one area to another requiring the expenditure of energy.

Amino acids and glucose move by active transport.

Metabolism Metabolism is the sum of the chemical

and physical changes continually occurring in living organisms and cells utilizing nutrients.

Anabolism is the formation and repair of body tissues.

Catabolism is the breakdown of body tissue into simpler substances.

Nutrient Transport Nutrients in the water soluble form, are

primarily carried by the blood in the animals body from where they are absorbed to where they are utilized.

Nutrients are used for maintenance, oxidation provides hear for body temperature and movement.

Nutrients are also used fro growth and fattening, fetal development, production of milk and eggs, wool and mohair and work.

Summary Digestion is breaking feed down into

simple substances that can be absorbed by the body.

Digestion occurs when feeds are broken up mechanically and acted upon by enzymes and other digestive juices.

Most absorption of nutrients after digestion takes place in the small intestine, although some absorption occurs in the rumen.