ANATOMY, PHYSIOLOGY & ABSORPTION OF NUTRIENTS

ANIMAL SCIENCE I

Digestive Systems

Objectives*

Name, locate and describe the functions of the parts of the digestive systems of ruminant and nonruminant animals

Classify farm animals as ruminant and nonruminant

Explain the relationship of types of digestive systems to the ability of ruminants and nonruminants to digest and absorb different classes of feed

Defining the Digestive Systems

Digestion-the process of breaking feed down into simple substances that can be absorbed by the body

Absorption-taking the digested parts of feed into the bloodstream

Digestive System (tract)-consists of parts of the body involved in chewing and digesting feed, absorbing nutrients and moving digested feed through the body

Parts of the Digestive System*

MouthEsophagusSmall IntestineLarge intestineRectumAnusAccessory organs

Teeth, tongue, salivary glands, liver, pancreas

Poultry Digestive System

No teethCrop and gizzardCecaCloacaVent

Digestive Capacities

Vary among speciesSpecies, age, breed and size affect capacityTable 5-3Ruminants are generally larger than

nonruminants

Ruminants

Animals that have a stomach that is divided into several parts Cattle, sheep, goats, llamas, bison, deer

Can digest large quantities roughage This is due to the bacteria present in their digestive

system. Bacteria produce proteins, B-complex vitamins and vitamin K

Nonruminants

Animals that have simple, one compartment stomachs Swine, horses, poultry

Require high energy, low fiber rations called concentrates

Ruminant vs. Nonruminant usage of roughage Cattle and sheep 44% compared to swine 22% Horses fall in the middle at about 39%

The Ruminant Stomach

Parts

RumenReticulumOmasumAbomasums

Rumen

Contain millions of protozoa and bacteriaMuscles help break the food down into

smaller particles so it is easier for bacteria to act

No division between it and the Reticulum

Reticulum

Hardware stomachForeign objects such as wire and nails go

here and are heldThick walls

Omasum

8% of stomachStrong muscles that grind up feed and

squeeze out some water but how much is not know

Somewhat of a mystery area

Abomasum

“true” stomach7% stomachFeed is mixed with gastric juicesDigestion is carried out here just like

nonruminants

How Ruminants Digest

Eat rapidlyDo not chew much of their feed before swallowingSolid part of the feed goes to the rumen; liquid

part goes into the reticulum then the omasum and on into the abomasum

In the rumen feed is partially broken down and mixed by bacteria. A slow churning and mixing takes place

When full the animal lies down and feed is forced back into the mouth and rumination occurs. Cattle chew their cud 6-8 times per day

Development of the Ruminant Stomach*

Abomasums is the only part that functionsYoung ruminants can not use roughagesMilk goes directly the abomasumsWhen born the rumen is small and found in the

upper left part of the abdomenAfter 2 months of age the rumen moves to its

normal positionThe reticulum and omasum grow and develop

rapidlyBy 3 months of age the rumen has grown enough

to begin to function

Digestion in Poultry

Possess certain special digestive organs not found in other animals Crop

Feed is stored and softened by saliva and secretions from the crop wall Muscular stomach

Lined with a thick, horny membrane like material called epithelium Feed particles are crushed and mixed with digestive juices by the gizzard

Ceca Two blind pouches where the small and large intestine join About 7” long Function is unknown but usually filled with soft, undigested food

Cloaca Enlarged part where the large intestine joins the vent

Vent Area of passage from the body for

Feces from the large intestine Eggs from the oviduct Urine from the kidneys

Absorption of Feed X

Most takes place in the small intestineVilli-small finger shaped projections are key

to absorption because they increase the surface area of the intestine

As substances are absorbed by the blood capillaries in the villi, they pass through the liver and then the blood

Water and dissolved minerals are also absorbed in the small intestine

Digested Protein

Absorbed in the form of amino acidsSome sodium must be present for absorption

to properly occur

Digested Carbohydrates (Starches & Sugars)

Present as monosaccharide's Glucose Fructose Galactose

Fiber

In the form of short-chained fatty acidsAdenosine triphosphate (ATP) supplies the

energy for the absorption of the monosaccharide's and fatty acids

Sodium must also be present

Digested Fats (soaps and glycerol)

Form into fats again and are absorbed by the lymph vessel in the villi.

They pass through the thoracic duct in the neck and into the circulatory system

Absorption in the Large Intestine

Water and some nutrients are directly absorbed into the bloodstream through capillaries in the intestinal wall

This is especially important in horses because much of the microbial digestion of roughage occurs in the cecum

End of the Nutrients Journey

Most in the muscle cellsSome are deposited in the liverUsed to replace worn out cells and build new

for energy or stored as fat for later use

Metabolism

Sum of the processes, both chemical and physical that are used by living organisms and cells to handle nutrients after they have been absorbed from the digestive system

Process

Anabolism—formation and repair of body tissue

Catabolism—breakdown of body tissues into simpler substances and waste

Oxidation of nutrients provides energy

Summary

Ruminants can use a lot of roughageThey have a 4 part stomach in which bacteria

breakdown the roughagesNonruminants must have more concentrates

such as grain, in their ration because they have simple one part stomachs

Most digested feed is absorbed in the small intestine of the animal

Small intestine has millions of tiny villi

Assignment

Discussion 24, 25, 27, 29-33, 35, 37Review Questions 1-11Due Friday Aug 31 end of period.