Ruminant Digestion

Probably the consistently most useful group of domesticated animals to humans has been the ruminants. Ruminants such as sheep, goats and cattle (dairy/beef) are important because they do not compete with the human food supply while providing a wide variety of products. Unlike us the ruminant is quite happy to graze on grasses all day and in many cases can survive in areas other types of domesticated animals would be unable. The key ingredient to this ability is the manner in which they digest their food.

Humans have many of the same digestive parts as ruminants. We each have teeth, esophagus, small intestine etc. It would become apparent, if you where to examine a cow's stomach closely that it is quite unusual. You would discover it looks totally different then ours. While we have one large chamber that makes up a stomach the ruminant has a stomach with four distinctly different chambers or compartments. They are called the reticulum, omasum, abomasum and rumen.

When a cow eats, the food is swallowed just like we do. They tend to chew their food less than we do so the food will not be ground (by teeth) and will appear to be rather course. The food is swallowed, passes down the esophagus into reticulo-rumen (reticulum and rumen). The food particles are exposed to the existing stomach contents, which exposes the feed to the microbes that live there. Unlike us, a cow will have a wide range of microbes that are used to help with the breaking down of the feed into volatile fatty acids, sources of protein vitamins etc.

Once in the reticulum-rumen the process of rumination begins. Cows can graze for quite awhile before they stop, lie down and begin ruminating or in other terms "chew their cud". The cow is able to regurgitate its food (bolus), which is rechewed then swallowed again. This process of regurgitation, rechewing and swallowing will occur for a period of time. Unlike us, the regurgitation doesn't not bother the animal since the stomach is always at a ph of about 7. The movement within the reticulo-rumen will also cause some of the finer particles to pass further into the digestive tract to the omasum and then finally into the abomasum.

The rumen composes the largest (75-80%) part of a cow's stomach and is located on the left side of the animal. The reticulum is much smaller and is found in front of the rumen. It's lining is very distinct with an appearance similar to a honeycomb. The omasum is located on the right side of the reticulum and its lining is often said to have "many plies". The abomasum, which is also called the "true stomach", sits below the omasum.

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