How Many Stomachs Does A Cow Have (And Why?)

Cows are ruminants, meaning they spend much of their time grazing and chewing their cud. But is all that chewing enough to break down the grass they eat?

It turns out it isn’t, and these bovids rely on a lengthy process to further break down the food they’ve chewed. In fact, these herbivores need a modified digestive system to process all that food efficiently, including multiple stomachs.

The Parts of a Cow’s Stomach

Quite often, the response to the question “How many stomachs do cows have?” is: four stomachs. In reality, cows have a multi-compartment stomach, which is very different from that of humans. When cows eat grass, it passes through the rumen, then the reticulum, the omasum, and finally the abomasum. Let’s take a look at the functions of the cow’s stomach compartments in more detail.

Rumen: Where Food Breaks Down

The first part of a cow’s stomach is the rumen. The rumen contains a lot of bacteria and acts as a storage area while the bacteria break down the cellulose, or fiber, in the plants the cow has eaten. Only bacteria can break down cellulose, and they do so through fermentation, similar to how yeast works. At this point, the food is not yet fully digested and is only partly broken down.

Unlike the human stomach, you won’t find any stomach acid here. If you watch a cow grazing, you’ll notice it taking in a lot of grass, hay, or other plant matter. It doesn’t chew the food like a horse does, but instead chews it just enough to moisten it and then swallows it whole. The food first goes into the rumen until it’s filled up. Because of the bacterial activity going on, the rumen is very warm, and the sides feel soft.

Reticulum: How the Cud Gets Chewed

Following the rumen is the reticulum. It’s where the food goes into after the rumen, and it allows the cow to regurgitate the food and start doing what’s called “chewing the cud” to break down the food into smaller pieces. The reticulum has bacteria in it, too. With the cow weighing an average of 1,400 pounds, it spends six to eight hours a day eating, and then another five to eight hours chewing cud.

Omasum: Absorbing Nutrients

After the reticulum is the omasum. When the cow has finished chewing its cud, it swallows the food again, and it then travels to the omasum. It absorbs water and some nutrients which were already broken down. Appearance-wise, it has several thin folds of tissue, which make it feel hard.

Abomasum: Fully Digested

Finally, there’s the abomasum, which is where the food is actually digested. The abomasum is considered to be the “true” stomach for all ruminant animals, akin to the human stomach, unlike the foregut, which is where fermentation takes place. It has stomach acid in it, but it may also have some bacteria that the rumen uses to break down the cellulose, and it is likewise digested. Any remaining food passes into the intestines.

Why Do Cows Have So Many Stomach Components?

Cows are herbivorous, which means they rely on plant matter. You could say its stomach is specialized to be able to fully digest the plant matter. Compare the digestive system of a ruminant herbivore, such as a cow, to that of a horse, which is a non-ruminant herbivore.

The four compartments of a cow’s stomach are called the rumen, reticulum, omasum, and abomasum. The grasses and other plants that cows eat are typically difficult to break down. That is why cows evolved with special stomachs: to help them digest these rough foods.

Ruminant herbivores include goats, sheep, bison, buffalo, deer, gazelles, antelopes, and giraffes. All ruminant herbivores have multi-compartmented stomachs with the same four parts. And unlike many other mammals, it has a longer small intestine to further absorb nutrients. Omnivorous and carnivorous animals have shorter small intestines, which are suited for the inclusion and digestion of meat in their diet.

The Importance of Digestive Health for Cows

Cows must chew cud for better health and milk production. But to do so, it needs to be relaxed and comfortable, usually while lying down. This activity encourages saliva to control the acidity level of the bacteria.

Not only is it important for farmers to be able to observe the cows chewing cud, but they must feed the cows a proper diet with enough fiber and low moisture, carbohydrates, and acidity. The right level of bacterial acidity in the foregut allows the bacteria to grow and function well in the rumen. Too low an acidity level and the bacterial growth will slow down, and the cow won’t be able to digest roughage and absorb the nutrients it normally would from chewing cud. Lactic acid builds up, and the cow’s immune system weakens.

It is a common saying that cows have multiple stomachs, but not how many or why. The reality is that they have multi-compartmented stomachs divided into four parts, including a foregut and a “true stomach.” Each part serves a different function for digesting the grass and other plant matter they chew. Such is a major feature of ruminators.