Goat Digestion
Written by Administrator-GL   
Sunday, 03 June 2007

 The Goat Digestive System- In Depth


Goats are ruminants, meaning they chew cud and have 4 stomaches. They are born a simple stomached or "monogastric" animal using only the true stomach -(abomasum); later developing the other three with the introduction of hay and browse.
With dairy goats in particular, the sooner they are introduced to hay the more the rumen will develop and the larger capacity they will have for food meaning more milk production.
Good quality feed is vital ~ free from dust and mold. A combination of hay , pasture (if available- I raised goats in dry lot for years before I moved to Missouri and had a pasture - so dry lot can be done successfully)and a pelleted feed or grain mix - free from mold!

 Simple Diagram of Ruminant Stomach


The Ruminant Stomach

Animals that regurgitate (bring food back up from the stomach into their mouth) and remasticate (re-chew) their food are called ruminants.
Ruminant stomach is adapted for fermentation of ingested food by bacterial and protozoan micro organisms.
Ruminant stomach has four compartments: THEY ARE: ~
Rumen: Volume Contents for the Rumen are between 12-28 liters, usually around 20 liters for an adult dairy goat.
Function~ The rumen serves as fermentation vat, organ of maceration (chewing) and grinding, bacterial digester, and organ of absorption. It allows for soaking and fermentation of bulk fibrous foods. The contents are continually being mixed. Rumen fermentation results in large quantities of gas, principally methane and carbon dioxide. Amount and rate of gas expelled is directly related to the type of feed the goat eats. Because of this, ruminants are prominent belchers, and if the belching process is inhibited, the animal will bloat. The mechanics of eructation (belching)are complex and vital. It is associated with secondary rumen contractions. Gas is allowed to enter the esophagus by the relaxation of it's lower sphincter diaphragm. The esophagus fills with the gas, the lower sphincter closes, and the upper pharyngo-esophageal sphincter relaxes. BURP. (there is really more to it than that but for the sake of not confusing you any more than necessary...) The pH in the rumen is usually within a range of 5-7.
Reticulum: Volume Contents for the Reticulum ranges between 1.6 to 2.3 liters.
Function~ Serves as pump that causes liquid to flow in and out of the rumen. Foods freely flow from the rumen to the reticulum and back. The reticulum is the second and smallest of the four compartments of the goat's 4-chambered stomach. The reticulum will hold the heavier substances from the rumen and serves as a muscular transit reservoir. If there are any non-food items like nails, rocks, wire.. the goat has swallowed it will end up in the reticulum. (Sharp objects may also continue their penetration through the diaphragm and into the pericardial sac. Organisms will then follow and invade the heart sac to cause traumatic reticulo-pericarditis (“hardware disease”) which causes increased fluid and gas formation (fermentation products) in the heart sac, constricting the heart. Heart failure develops. One method used to prevent migration of metal objects is to place a magnet in the reticulum. Unfortunately, galvanized nails, copper wire and other non-magnetic objects move freely and may still cause hardware disease. NOTE:~Contraction of the reticulum aids in the rumination process, but is not vital. Rumination will occur even if the reticulum is removed.~
Omasum Volume Contents for the Omasum ranges between .75 to 2.1 liters.
Function~ Provides for continued fermentation and absorption of feed stuffs. Feed passes into this 3rd compartment. Here, excess moisture is removed from the ingested feed, and finer grinding occurs as well, even after rumen-recticular fermentation. The omasum is not involved in the rumination process.
Abomasum Volume Contents for the Abomasum ranges between 2.1 to 4.0 liters.
Function~Feed then passes into the abomasum, or true stomach. Glandular secretions of gastric enzymes and hydrochloric acid are produced, and it's functions are similar to the stomach of monagastric (single stomach) animal. The abomasum consists of 3 parts, the fundic, body and pyloric regions. The pyloric region joins the small intestine, separated by the pyloric sphincter muscle. Glands of the fundic area, near the omaso-abomasal orifice, secrete a mucus which protects the walls of the abomasum from protein-degrading enzymes and hydrochloric acid. The fundic glands are the most important for digestion. A specialized secretion from the fundus combines with vitamin B12 to stimulate the production of red blood cells. The acidity of the abomasum usually remains close to a pH of 3.

Gastric juice consists of water, inorganic salts, organic substances and hydrochloric acid. Between 4 to 6 liters per 24 hrs are secreted in goats. The enzymes; rennin, pepsin and gastric lipase are part of the gastric juice. Rennin is the enzyme for milk coagulation, acting on milk casein by producing a gel-like mass, in preparation for the protein digestion by pepsin.
Further breakdown of proteins does not occur in the abomasum.
The chyme (liquid part of the feed) leaves the stomach and reaches the small intestine.
Small Intestine
Function~ Feed passes from the abomasum into the duodenum, the first segment of the small intestine. Then into the large intestine.
Large Intestine
Function~ To remove water from the intestinal contents and to concentrate the feed residues for excretion. In order to maximize water removal efficiency, the large intestine causes delay in the rate of passage of intestinal contents. While feed may transverse through the small intestine in about 3 hours, it takes approximately 18 hours to move through the large intestines. This is especially impressive considering that the large intestine of goats is only about 6 1/2ft long, while the small intestine is almost 36ft long. A good deal of absorption of the nutrients occurs here. The large intestine's functions are mainly to resorb the water from the digesting foods. This is an important role in water conservation .. the dry fecal matter is good evidence of this. Goat berries are formed in the last part of the large intestine. The last foot of the large intestine, the rectum, is a modified storage organ for the fecal material. Upon accumulation of sufficient amounts, nervous stimulation triggers defication. The anus is located at the termination of the digestive tract. It is made up of two sphincter and a retractor muscle, all of which are normally closed, except during defication.

*Studies of goats have indicated that it takes about 11-15 hours for feed material to pass through the digestive system. Maximum excretion is achieved in about 30 hours but does not reach completion until 6-7 days later.

The ruminant digestive system of the goat, works non-stop throughout the adult life of the animal. Other animals have digestive organs and secretions that alternate between periods of stress and inactivity, while the goat must continually manufacture digestive juices and enzymes 24 hours a day every day of it's life. A breakdown in this complex process for even a brief period can result in acute and potentially deadly situation for the goat.


A Few Facts

1. Goats eat vegetable matter, they use their lips in selecting food unlike cows who use their tongues.
2. The bottom jaw is slightly wider than the top and the goat will chew slightly in a lateral direction.
In this way the inner edge of the sharp lower molars and the outer edge of the sharp upper molars is what chews the food. A goat can only chew on one side at a time. Simply put, saliva from different portions of the inside of the jaw and mouth contains water, electrolytes, mucus and enzymes, all of which aid in the beginning of the digestive process.
esophogeal groove

The feed is chewed only enough to make a small bolus, small enough to swallow. Saliva functions primarily as an aid to digestion and in a goat is produced in fairly large quantities.. A goat will produce approximately 10 liters or more a day!

3. Gastric secretion called rennin in a young kids digestive system, coagulates milk protein into solids for digestion and absorption. This is the same source as "rennet" used in cheese making.
By Products of Fermentation
Methane (30-40% of rumen gas)
Carbon Dioxide (60-70% of rumen gas)
Gases mostly eliminated by belching
Volatile Fatty Acids

When baby kids eat, the milk goes directly into the abomasum or True Stomach until they have developed the rumen which happens in about 3-4 weeks and continues to develop for months thereafter. (This is important to remember because if you have a sick kid, giving it a probiotic or other rumen stimulating medication will not help it as it is not using the rumen to digest it's food.)

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Last Updated ( Sunday, 06 January 2008 )