Ask the Vet

Bark-Eating Cows

A group of bored cows can sometimes find odd ways to spend their time. (PF photo by Jim Patrico)


My cows just started eating the bark off of my trees? Why are they doing this?


This behavior actually has a name, “pica.” It refers to the habit of eating something not normally considered food, and it can occur in all animals.

One of my favorite episodes of that classic sitcom “M*A*S*H” was when Klinger decided to eat a Jeep in his continuous attempt to get out of the army. I guess you could call that pica.

Some researchers believe when cattle do this, it's due to some sort of nutrient imbalance. Cattle on lush pastures, for example, may be deficient in fiber the rumen needs for proper functioning. Some mineral deficiencies, including those tied to low phosphorus, potassium, copper and magnesium consumption, have been linked to pica. Even low-protein diets have been looked at as the culprit.

So, what does bark have going for it? It is high in fiber, and it does contain minerals and protein. So, there's the possibility your cattle are low in these areas.

A good first step is to evaluate your herd's nutritional program. This is going to be key to peak performance and profitability in any herd. If cattle are thin, they may need supplemental feed for additional energy, and/or they may need additional protein.

Cattle also must have a balanced mineral program. A trace mineral block is not adequate. Minerals can be supplied a few different ways; most commonly, they are in supplemental feed, in lick tubs or probably loose minerals in some type of feeder.

It's not enough to just supply minerals; you need to be sure the cattle are consuming them. So, think about palatability when choosing a mineral, as well as how well it fares out in the elements.

And, while those are all of the scientific reasons cattle will eat bark off of trees, there's one more: In some cases, I am convinced cows just get bored. This can simply be a bad habit, but one that cows can teach each other.