Do Deer Chew Cud?

Do Deer Chew Cud

You might have heard the expression, “Don’t chew like a cow”. But what does that even mean? Cows have a unique way of chewing their food and you can see that they are constantly chewing. That is a bit strange!

Why do they constantly have to chew their food? Well, it is because of the food they eat: grass! The grass is very hard to chew due to the presence of cellulose cell walls. To get the most nutrients out of the grass, a cow has to constantly chew. Usually what they chew is known as cud.

Do deer, like cows, also chew their cud? The answer is yes! Cows and deer have a very similar digestive system where they have to constantly chew their food to get the most out of what they eat. So if you observe a deer, you will also notice that they constantly chewing as well!

Want to know more about deer and how they chew their cud? Read on and find out all about the deer and cuds!

Key Takeaways

  • Deer belong to a family of animals called ruminants, a type of herbivore that absorbs nutrients through a process called fermentation.
  • Deer constantly chew their cud to help break down the cellulose in the grass they eat and prepare it for digestion in the stomach.
  • A deer has four stomachs – the rumen which stores the cud, the reticulum which filters the cud, the omasum which absorbs the water from the cud and the abomasum which fully digests the cud.
  • The way that deer chew their food sideways to grind the cud into smaller pieces and crush it with their tongue.
  • Deer typically like to eat: grass, sedge, tree shoots, fruits, flowers, and tree bark.

What are Ruminants?

What are ruminants
What are ruminants?

Let’s get to know more about the four-legged animal known as deer. Deer are herbivores, meaning that they eat plant-based food like grass, leaves, berries, etc. They are also known as ruminants, just like cows! A ruminant is a type of herbivore that absorb nutrients through a process called fermentation in their stomach.

What is fermentation in a ruminant?

Well, it is a chemical process where the plant-based food that the deer and other ruminants eat is broken down for nutrients. These are digested with the help of biological catalysts called enzymes that live as microbes in the stomachs of ruminants. You might think microbes, like bacteria, might be harmful to these animals. But in fact, these microbes are the helping kind, living in a symbiotic relationship where the two organisms work together to help each other.

Ruminants like deer are dependent on these microbes to help them digest the grass that they eat. Deer don’t have the enzymes necessary to get the nutrients and energy from the grass that they eat. That is why these microbes are essential in helping deer survive!

What is a Cud?

What is a cud
What is a cud?

Don’t be grossed out by this part, but in order to digest grass properly, deer regularly bring out the semi-digested food from their stomach back to their mouth and chew it. This is known as the cud. It is usually the size of a lemon, and deer have to constantly bring this out of their stomach and constantly chew it.

Why do they have to chew what was in their stomach?

Well, the digestive system of a deer is very different from a human. Our digestive system requires food to enter once. But because of the complex way that grass and other raw plant-based food have to be digested, the cud has to go back and forth between the mouth and stomach many times!

Why do deer constantly chew their cud?

This is why you might see cows and deer constantly chewing their food! Usually, deer have to move around constantly and so they quickly swallow their food before chewing. Then later, they sit and start chewing on their cud while they are resting. A very convenient way of eating as deer are constantly in danger of hunters and predators in the wild.

How The Cud is Digested?

Like their special microbe enzymes, the deer have a digestive system that is unique to ruminants. The stomach has four distinct chambers where digestion takes place. Each of these chambers has its own function of digestion to help absorb the nutrients. Let’s discuss the function of these four chambers and how the cud is moved around in a deer’s body.


The first chamber of the stomach is known as the rumen. This food eaten by the deer is transferred from the mouth to the rumen via the esophagus. Here, most of the initially swallowed food, mainly grass, is stored. As it fills up, the cud is transferred back to the mouth in small portions for the deer to chew it again. Usually, the deer chew their cud when they are resting on their bedding away from potential dangers.


Where the rumen acts as the storage, the reticulum can be considered the filter. The cud that is chewed and swallowed back into the rumen is passed on to the reticulum. Here, the main digestion through fermentation takes place. The microbes attack the cellulose inside the grass and help break it down. This semi-digested cud is then transferred back to the rumen to be transferred back to the mouth to be chewed again into smaller pieces. And then it is swallowed again, carried back to the reticulum, and digested further. This process continues on and on until the cellulose in the cud is fully broken down before it is taken to the third chamber.

Fun fact, the cud in the reticulum needs about 16 hours of digestion to help break down the cellulose completely!


We have gone through the storage and the filter. Now we come to the absorber known as the omasum. The reticulum filters small pieces of cud that have all cellulose broken down and transfers it to the omasum. The omasum’s job is simple; absorb all the water from the cud and transfer the nutrients in that water to provide the deer with energy. Once all the water is absorbed from filtered cuds, they are again taken back to the mouth to be chewed one final time.


We have reached the final stage of digestion in the fourth stage of the stomach known as the abomasum. Here, the digestive juices help completely digest the cud and absorb the nutrients. The remaining bits are passed on to the small intestines to be later turned into waste that the deer passes out of its body.

Quite a journey a small cud has to go through before it is finally digested into the nutrients that the deer need to move around and survive.

How Do Deer Chew Cud?

How do deer chew cud
How do deer chew cud?

After reading about how the cud is digested, you might want to know how the deer chew their cud. As they are constantly chewing, the way that they chew also helps in digestion.

Chewing sideways

Due to how their teeth and jaw are arranged, the deer chew their cud sideways. Normally humans chew in an up-and-down motion. But the deer chew their cud sideways, grinding it to be as small as possible to maximize the surface area where the enzymes act upon it.

Crushing the cud

What the deer also does during their chew is crush the cud with the tongue against the roof of their mouth. This helps transfer all the water directly from the mouth to the omasum to be absorbed as nutrients and energy. Because of how long it takes to fully digest a simple cud, the deer can get some much-needed energy in this way.

What can Deer Eat?

As herbivores, deer can eat a lot of plant-based food such as:

  • Grass
  • Sedge
  • Tree shoots
  • Fruits (pears, apples, and a variety of berries)
  • Flowers (daylilies, roses, tulips, pansies, etc.)
  • Tree bark (when food source is scarce)


What are the names of the chamber inside a deer’s stomach?

In the following order, they are: the rumen, reticulum, omasum, abomasum.

Do deer chew like cows?

Yes, deer chew their cuds sideways like a cow.

Why do deer constantly chew?

They have to constantly chew their cud otherwise the stomach will not be able to digest the cud properly.

Do deer swallow their food?

They have to swallow their food many times to be able to break down the cellulose inside the grass they eat.

Final Thoughts

As ruminants, deer have a long digestive process. They don’t have the time to peacefully chew the grass. Instead, they have to swallow the grass and wait to chew on their cud when they are safe in their bedding. This process may be long, but it helps the deer get the maximum nutrients from the grass they eat. They constantly have to chew their cud, otherwise, they will not be able to get the necessary energy to survive.

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