Ask the Vet

The Inside Story: Cows and Cud

If cattle don't get enough long-stem fiber, cud chewing is reduced. (Progressive Farmer image by Gregg Hillyer)

When we had a cow that was sick, my grandfather would say, "She lost her cud." He liked to see most of the cows laying down and chewing their cud. He seemed almost obsessed with this, but I have never known why cows chew their cud, and is it as important as he thought it was?


Cud chewing is an essential part of what makes a ruminant a ruminant. The rumen is this giant fermentation vat where microorganisms break down parts of forages that simple-stomached animals can't digest. These microorganisms also allow ruminants to utilize nonprotein nitrogen (urea) to manufacture protein.

When cattle consume grasses or hay, it enters the rumen, and the digestion process begins. When the cow is resting, she will regurgitate a bolus of this semidigested food and chew on it. This process breaks down the forage particles making them more available to rumen microbes. Equally important, this produces a huge amount of saliva, which has an alkaline pH. When the saliva is swallowed, it acts as a buffer and keeps the rumen pH from becoming too acidic.

High levels of grain in rations decrease rumen pH and change the balance of rumen microbes to those that are more efficient at digesting carbohydrates. If cattle don't get enough long-stem fiber, cud chewing is reduced. That increases the chance of a digestive disorder called rumen acidosis. With acidosis, the whole rumination process is reduced or collapses, and the cow stops eating. This can be very serious and, in some cases, even life-threatening.

So, your grandfather was right. Cud chewing is important and a sign of healthy cows. The rumen is your cow's best friend. It's what gives her the advantage over other simple-stomached livestock. To take care of cattle, we must understand and take care of that rumen.


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