THE GOAT DIGESTIVE SYSTEM

Goats are ruminant animals. Their digestive tracts (which are similar to those of cattle, sheep and deer) consist of the mouth, oesophagus (the oesophagus is a muscular tube in the chest that connects the mouth and throat to the stomach), four stomach compartments, small intestine and large intestine.

Like other ruminant animals, goats have no upper teeth. Goats depend on the dental pad in front of the hard palate, lower incisor teeth, lips and tongue to take food into their mouths.

The Four Chambered Stomach Explained!

Rumen: This is the largest of the four stomach compartments of ruminant animals. The capacity of the rumen of goats ranges from 3 to 6 gallons depending on the type of feed. This compartment, also known as the ‘paunch’, contains many microorganisms (bacteria and protozoa) that supply enzymes to breakdown fibre and other food that the goat eats. The conversion of the cellulose of feeds to volatile fatty acids (acetic, propionic, and butyric acids) is the result of microbiological activities in the rumen. These volatile fatty acids are absorbed through the rumen wall and provide up to 80 percent of the total energy requirements of the animal. Microbial digestion in the rumen is the basic reason why ruminant animals effectively utilize fibrous feeds and are maintained primarily on roughages.

Rumen microorganisms also convert components of the feed to useful products such as the essential amino acids, the B complex vitamins, and vitamin K. Finally, the microorganisms themselves are digested further in the digestive tract.

Reticulum: This compartment, also known as the ‘hardware stomach’ or ‘honeycomb’, is located just below the entrance of the oesophagus into the stomach. The reticulum is part of the rumen separated only by an overflow connection, the ‘rumino-reticular fold’. The capacity of the reticulum of goats ranges from 1 – 2 litres.

Omasum: This compartment, also known as the ‘manyplies’, consists of many folds or layers of tissue that grind up feed ingesta and remove some of the water from the feed. The capacity of the omasum in goats is approximately 1 litre.

Abomasum: This compartment is more often considered the ‘true stomach’ of ruminant animals. It functions similarly to human stomachs. It contains hydrochloric acid and digestive enzymes that breakdown food particles before they enter the small intestine. The capacity of the abomasum of goats is approximately 4 litres.

As partially digested feed enters the small intestine, enzymes produced and secreted by the pancreas and small intestinal mucosa further breakdown feed nutrients into simple compounds that are absorbed into the bloodstream. Undigested feed and unabsorbed nutrients leaving the small intestine pass into the large intestine. The functions of the large intestine include absorption of water and further digestion of feed materials by the microorganisms present in this area. The 30 meter long intestinal canal of goats has a capacity to hold 12 litres.

When a goat kid is born, the rumen is small and the abomasum is the largest of the four stomach compartments. The rumen of a goat kid represents about 30 percent of the total stomach area, while the abomasum represents about 70 percent. Hence, digestion in the goat kid is like that of a monogastric animal. In the suckling goat kid, closure of the oesophageal groove ensures that milk is channeled directly to the abomasum, instead of entering the rumen, reticulum, and omasum. When the suckling goat kid starts to eat vegetation (first or second week of life), the rumen, reticulum and omasum gradually develop in size and function.

Goats are very particular about what they eat, they will not consume food of poor quality or food that is dirty or has been trampled on, unless you have have been putting them on a starvation diet. Goats require the best quality grass, green stuffs and concentrates. However goats will eat a wide range of food, preferring more fibrous food to lush grass. Goats will eat young thistles and brambles, as well as twigs, they also like bark from trees. Goats are inquisitive and will nibble and investigate most items, however, they are selective about what they actually eat.

THE DIGESTIVE SYSTEM OF THE GOAT

The goat are a group of animals called Ruminants derived from the word Ruminate (chew their cud). Ruminants have special four-compartment stomachs especially designed to digest roughage (food high in fiber) such as grass, hay and silage.

Their stomach has four chambers: 1) the Rumen, 2) the honey-comb like Reticulum, 3) the Omasum, and 4) the Abomasum. The size relationship of the four chambers changes as the animal grows up. The abomasum will proportionally smaller. To understand why this happens, you need to consider the individual function for each chamber and then look at the goat’s diet.

1) The Rumen acts as a big fermentation container. Bacteria and Protozoa in the Rumen supply the enzymes needed to break down the fiber in the goat’s feed. This is similar as to how bacteria can ferment the sugars in grape juice to make wine. 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.