EQUUS CONSULTANTS

What’s behind selective grazing?

Q:I bought a 12-year-old horse two years ago. I have seven acres of lush fescue, cross fenced into three pastures. He is my only horse and is rotated to a different turnout once a month. He always ignores the best grass and goes back to certain areas where he chews the short grass down until those spots are in danger of dying.

I tried erecting electrified wire to protect a couple of the areas where he was killing grass, but he’s gone so far as to just take the shock and knock the wires down. Currently, I am picking up his manure and spreading it in the areas that look the worst so he avoids them. I’m aware of rotational grazing on a smaller, more intensive scale, but it is too labor intensive for me to manage.

I did wonder if this might be a dental issue---if he might be having a problem cropping longer grass. I know my horse was on a dry lot for two years before I bought him, but I have no other information about his history. He eats his grain and hay very well. He was examined by

an equine dentist recommended by my veterinarian soon after I got him, and his teeth were rechecked seven months ago by another veterinarian, who said they were in pretty good shape.

If this is a dental issue, what should I look for and what questions should I ask my dentist on the next visit? Do you have any further suggestions to help me protect my pastures from overgrazing?

Name withheld upon request

A:I do not believe your horse has a dental problem. You are to be commended for having his teeth examined regularly because older horses can have a variety of dental issues. But given that your horse is eating hay and grain with no difficulties, and two professionals have examined him and found no significant problems, it’s safe to say that his grazing behavior isn’t caused by his teeth.

Your horse is exhibiting a behavior called selective grazing. Horses don’t eat plants in propor-

tion to their abundance in the pasture. Rather, they choose each bite based on the taste, smell and tactile properties of the grasses. Horses tend to like certain plants better than others and certain heights of plants better than others. Individual preferences can vary, but most horses---like yours---prefer shorter grasses over longer grasses. Short grass is usually younger, more tender and more nutritious. Your horse isn’t trying to deliberately ruin your pasture. He is simply eating what is best for him.

So how do you protect your pasture? Horses do avoid their own feces while grazing, so spreading manure as you have been doing is one behaviorally sound solution. However, that isn’t your best option because you may expose your horse to a higher parasite load. Avoiding feces is probably a behavior that evolved to protect horses from internal parasites.

A better approach would be to make the uneaten grass more appealing. I suggest simply keeping the longer grass mowed down to stimulate the growth of younger, more tender and more palatable new shoots. Katherine A. Houpt, VMD, PhD,

DACVB Animal Behavior Clinic Cornell University Ithaca, New York