NEW YORK STATE 4-H MEAT GOAT PROJECT FACT SHEET #14

by Suzanne Raupp
Revised April 1999
by Dr. tatiana Stanton
Cornell University, Ithaca , NY 14853

THE DIGESTIVE SYSTEM OF THE GOAT


The goat is a member of a class of animals called ruminants.  These animals ruminate (chew their cud).  Unlike us, they have special four-compartment stomachs especially designed to digest roughage (food high in fiber) such as grass, hay and silage.  

The goat’s stomach has four chambers: 1) the rumen, 2) the honey-combed reticulum, 3) the omasum, and 4) the abomasum or true stomach.  The size relationship of the four chambers changes as the animal grows up.  The abomasum gets proportionally smaller.  To understand why this happens, let’s consider the function of each compartment and then review the goat’s diet.

1) The rumen acts as a big fermentation vat.  Bacteria and protozoa in the rumen supply enzymes to break down the fiber in the goat’s feed.  This is similar to how bacteria can ferment the sugars in grape juice to make wine in big wine barrels.  The tiny organisms in the rumen also help to build proteins from the feed and manufacture all of the B vitamins needed by the goat.  Many nutrients that help provide the goat with energy are also absorbed here.  The fermentation process produces heat that helps to keep the goat warm. 

When roughage is eaten by the adult goat, it is chewed on, soaked with saliva, and then swallowed.  This bolus of food is called “the cud”.  It goes down into the rumen to be attacked and broken down or digested by the micro-organisms. At regular intervals the cud is brought back up to the goat’s mouth to be chewed on some more and then swallowed again.  This entire process is called rumination.  If you watch the goat’s neck carefully, you can see him swallow and later regurgitate his cud.  The goat will often burp to get rid of the gas produced by all the fermentation going on in his rumen.  You can really smell the fermentation process on his breath.  If something causes the goat to stop being able to burp up the gases, the gas will build up and bloat or swell up his rumen and he may become very sick with “bloat”.

2)  Once the food particles of cud become small enough, they pass to the second compartment or reticulum.  Here any foreign objects that may have been accidentally swallowed with the feed settle out in the honeycomb structure of the reticulum’s  walls.  Another name for the reticulum is the  “hardware stomach”.

3)  The fermenting particles then pass on to the omasum.  The omasum removes the water from them and also absorbs more nutrients called volatile fatty acids that help supply the goat with energy.

4)  The particles are then forced into the abomasum or true stomach.  Here, the particles are digested by the stomach acid, hydrochloric acid (HCl).  This form of digestion is the same as what occurs in our stomachs.

The remaining particles are then passed on to the small intestine where most of the nutrients are absorbed by the body and made available to the goat.

When a goat kid is born, its rumen, reticulum and omasum are very tiny and not useful.  The goat kid depends on a liquid, milk, not roughage for its feed source.  When the kid swallows milk, the milk goes directly to the abomasum through the esophageal groove. Everytime the kid swallows, a flap of skin at the entrance to the rumen folds over to form a grove that bypasses the rumen and sends the milk straight to the abomasum to be digested by stomach acid.  As the kid gets older,  he starts trying to consume roughage.  The rumen becomes active and starts to enlarge.  Its population of micro-organisms increases. The reticulum and omasum also respond to the changes in diet by getting bigger.  By the time the kid is an adult goat, roughage is his main source of food and his rumen is far larger than his abomasum.

KID                                                                                         ADULT

 

1- rumen, 2 - reticulum, 3 - omasum, 4 - abomasum


Suggested Activities

  1. Get some human cereals (baby  food yogurt or custard, rice crispies and shredded wheat). Put a 1/4 cup of each in separate unstarched cotton spice bags or squares of cotton cloth.  Boil them covered in a solution of 1 tablespoon of neutral detergent soap (i.e., baby shampoo) per cup of  water in a sauce pan for one hour.  This will digest all the nutrients but the fiber from them.  After boiling, rinse the bags in cold water, gently squeeze dry, and open.  Which foods had more fiber? Which would be easiest for a kid to digest? *  

  2. Do the same experiment using milk replacer, a complete pelleted calf or lamb ration, various grains, hays, and sttraws.  Which ones have more fiber? For more advanced 4 - H er’s, weigh out 100 grams each of the feed samples rather than a 1/4 cup.  After boiling, oven dry them at  500 F and reweigh them to compare fiber content.


  3. Watch a goat chew his cud. *  Try to time how many times a goat brings up his cud in 15 minutes.


  4. Invite a veterinarian to come talk to your 4 - H group about bloat and other metabolic diseases that can occur when something goes wrong with your goat’s digestion. *


  5. A rumen fistula is an artificial opening that allows scientists to look inside the rumen of an animal.  Contact an agricultural college that has a fistulated cow, sheep or goat and take turns examining the animal’s rumen.


  6. Obtain a clean and rinsed out digestive tract of a sheep or goat from a slaughter house and lay it out on a lawn to examine and identify the different parts.  Measure the length of the different parts including the small intestine.


* Activity  is suitable for Cloverbuds.

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