Ask The Vet

The Inside Story: Cows and Cud

Image by Gregg Hillyer

Q: 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?

A: 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.

Q: I have a cow that has developed a large swelling on her lower jaw. It does not seem to bother her. Is this something I need to have checked out?

A: The short answer here: yes. Many of these types of swellings are simple bacterial infections.

If a cow consumes a piece of wire or a sharp stick, and it breaks the skin, or it has a puncture wound on the lower jaw, it’s easy for an infection to get started. Initially, this infection spreads between tissues and is called cellulitis. The affected area can be very hard, painful and warm to the touch.

This infection will usually “organize” itself into an abscess (pus pocket) that may rupture and drain. In some cases--especially with certain bacteria like Actinomyces bovis--the infection can spread to the mandible (jaw bone). This is called lumpy jaw or actinomycosis.

Cellulitis can often be treated with antibiotics. Abscesses are best treated by lancing, draining and flushing, and then giving antibiotics. Antibiotics don’t penetrate the abscess well, so draining the pus pocket is by far the most important part of the treatment.

Once we are looking at actinomycosis, it’s a much more difficult condition to treat. The treatment of choice is sodium iodide given in the vein slowly and repeated several times. Antibiotics are given at the same time. Treatment is not always successful, and caution must be used in pregnant cows.

This is a condition where your veterinarian will want to be sure of a diagnosis before treatment. The two of you will have to make a hard decision on whether it’s cost effective to treat the animal at all.

Please contact your veterinarian for questions pertaining to the health of your herd. Every operation is unique, and the information in this column does not pertain to all situations. This is not intended as medical advice, but is purely for informational purposes.

Write Dr. Ken McMillan at Ask The Vet, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email


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