Why Do Cows Have 4 Stomachs ?

First, we need to debunk the myth that cows have four stomachs. Instead, a cow has four different chambers in a single stomach. So, we start by rephrasing the question “Why do cows have 4 stomachs?” into “Why do cows have a 4-chambered stomach?”

cow
Cows feed on hard-to-digest, fibrous food, Credit: depositphotos.com/Khaligo

Why do cows need a 4-chambered stomach?

Cows spend a third of their day feeding and another third chewing the cud. They masticate the food with the help of teeth on the lower jaw and the hard dental pad (cows don’t have teeth in their upper jaw). They feed on grass and grains rich in starch and cellulose. Cellulose is hard to break down. The gut microbiota is important in breaking down cellulose in cows or other cattle animals.

What are the parts of a cow’s stomach?

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Left side view of a four-chambered ruminant stomach, Credit: extension.msstate.edu

Mammals with four-chambered stomachs are called ruminant organisms. Most cattle animals possess a ruminant stomach. In this blog, we will discuss about a cow’s stomach.

The four parts of a cow’s stomach are the rumen, reticulum, omasum, and abomasum. Each of them has a different function.

Rumen: The rumen or the “paunch” is the largest chamber of a cow’s stomach. Ingested food travels down the esophagus into the rumen. It can hold 25 gallons of food at once. The rumen acts as a silo where all the food is stored into.

The food is fermented in the rumen with the help of microbes. Generally, cows feed on grass and grains, which are major sources of starch and cellulose (plant fibers). The rumen microbiome consists of starch-breaking amylolytic bacteria, amoeba, methane-producing microbes called methanogens, protozoa, and fungi. Cellulolytic bacteria and fungi break down cellulose.

The fermentation yields volatile fatty acids, which the rumen then absorbs. The rumen has tiny bumps called papillae, which increase the surface area and allow better absorption of fatty acids and other nutrients. The rumen is supplied with a good blood supply, which further enhances the absorption of nutrients.

Cows regurgitate the semi-digested feed called cud, and they rechew the cud to break it down further, a process known as chewing the cud. Rumen also uses simple nitrogen compounds to produce proteins, whose content is otherwise poor in grass and grains.

Reticulum: Reticulum is a chamber located close to the heart. A flap of tissue separates the rumen and the reticulum. Thus, the two chambers are together called reticulorumen. The tissue in the reticulum forms a honeycomb-like pattern. The reticulum acts as a checkpoint. It keeps larger food particles in the rumen while smaller food particles (digesta) are passed into the omasum.

Sometimes, cows can ingest nails or other sharp objects. These get lodged in the reticulum and puncture the inner linings of the chambers. If left untreated, they can cause ‘hardware disease’, where the perforations lead to the infection.

Omasum: Water is absorbed from the digested feed in the omasum. It has tissues arranged like pages. Cows have a large omasum. Digested food enters into the omasum from the reticulum. In young ruminants that still drink milk, the esophagus directly opens into the omasum, bypassing the rumen and reticulum.

Abomasum: Abomasum is the final chamber of a ruminant stomach. This is the “true” stomach in the sense that it bears similarity to a non-ruminant stomach. This is the only chamber with glands. It produces hydrochloric acid and pepsin, which breaks down proteins. The abomasum receives lipase from the pancreas. All these secretions prepare the proteins for absorption in the small intestine. It also contains chief cells, which produce mucus. The mucus protects the inner lining of the abomasum from acid damage.

It is wonderful to think that the cow’s stomach is a microbiome. Many species of bacteria, fungi, and protozoa living in the cow’s gut have been identified, and we can only fathom how many more will be discovered as time passes.

Copyright @smorescience. All rights reserved. Do not copy, cite, publish, or distribute this content without permission.


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