Rumination—or Cud Chewing

Cud chewing is a part of the digestive process for all ruminants, a class of animals to which cows belong.

Juicy Fruit? Dentyne? Bazooka? What kind of chewing gum do cows like best? Actually, they prefer chewing their own cud (regurgitated feed). While this may sound a little repugnant, cud chewing plays an important role in cow health and productivity.

Ever wonder why it looks like a cow is chewing gum?

Rather than politely chewing and then swallowing their food, cows take in feed rapidly and do not chew it before swallowing. After swallowing the feed, they “burp” and regurgitate the partially digested feed and chew it again to form a “cud” (similar to chewing gum).

Why don’t people chew cud?

Humans have one stomach, whereas cows have a four-compartment stomach, which allows them to digest forages (for example, hay, grass and corn silage [see Corn Silage]) and gain valuable nutrients and fiber from these forages. People aren’t so lucky.

The four compartments of a cow’s stomach are called: reticulum, rumen, omasum and abomasum [see diagram]. First, the liquid portion of cow feed goes to the reticulum and the solid portion goes to the rumen, where it softens. Beneficial “bugs” (rumen bacteria) break down feed in the rumen. When feed has been broken down enough, it passes to the omasum, which efficiently absorbs water and salts released from the partially digested feed. The abomasum, considered the “true stomach,” functions similarly to a human’s stomach, digesting feed chemically, rather than mechanically or by fermentation, like the other three chambers of a ruminant’s stomach.

When cows chew their cud, which they do for about 8 hours a day, they secrete saliva—just like humans do when they chew gum. Saliva contains a natural antacid (similar to baking soda), which buffers a cow’s rumen. Proper buffering allows cows to digest plant matter—much of which humans can’t utilize. The amount of time a cow spends chewing her cud highly correlates with her overall health. Inadequate cud chewing may indicate an “upset stomach,” which can lead to reduced feed intake; lower milk, butterfat and protein production; decreased rumen bug population; and lameness.

So, from the initial bite, to swallowing feedstuffs whole, to regurgitating feed and forming and chewing cud, and to reswallowing the feed, cows partake in a fairly complex digestion (rumination) process. Yet, rumination helps cows efficiently turn grass and corn (and other feedstuffs, food processing byproducts, minerals and vitamins) into nutrient-dense milk.

When you see a cow chewing her cud, you know she’s content, comfortable, healthy, happy and making milk for you to nourish your body.