A taste for plastic?

Q:My 10-year-old Appaloosa mare loves anything plastic. She gnaws on her feed bucket unless I stand right over her. If I move away she bites the edges of her feed bin. She tries to suck down the worming tube and will gobble up anything plastic that she can find in the pasture. A few years ago she reached into our cart storage area and took a big bite out of the seat. The utility companies are constantly putting those little plastic flags along the right of way and she will eat every one she can find. I have tried painting her feed bucket sides with a mixture of jalapeno and habanero peppers but she just licks it off.

Our three other horses don’t do this. We feed a good-quality grain along with a vitamin supplement. This mare is otherwise healthy and has all her vaccinations up to date. The veterinarian can’t explain this behavior except to say she just loves plastic.

I am on a constant hunt for plastic marking flags in our pastures. I worry that one of these days something plastic will cause an impaction or the metal on those utility flags will lodge in her digestive tract. The utility companies are forbidden to come on our land without notice but they often sneak in and plant those flags without our knowledge.

We love this mare very much. She is quite a character and my husband’s favorite. Any suggestions will be greatly appreciated. Lynda Edwards Montgomery, Texas

A:It is interesting that hot sauces do not deter your mare. Creosote---chemicals derived from tars that are used in preservatives, antiseptics and a variety of other products---seems to be the only taste that most horses dislike, but it is better to determine why your mare likes plastic rather than punishing her attempts to ingest it.

The behavior she is exhibiting is called pica, which is defined as eating non-feed objects. Horses do occasionally have pica, and dirt eating is one type. One case I worked with was a foal whose dam had died at his birth and who, despite expert nutritional recommendations, had diarrhea and ate dirt, possibly indicating a kind of nutritional wisdom because clay (kaolin) is a treatment for diarrhea. In other cases, the dirt may contain an element the horse is lacking, in particular, iron.

I cannot imagine what nutrient is contained in plastic---a petroleum product---so your mare’s interest in ingesting it may be related to some other aspect of her management. Many horses eat wood, but chew less of their barn and fences if the amount of fiber in their diet is increased. You mentioned that you feed your mare good-quality grain and a vitamin supplement but you don’t say how much hay she receives. It’s possible your mare hunts for plastic in her pasture because there isn’t enough grass for her to browse and consume. Free-ranging horses spend 60 percent of their time grazing, and horses in stalls spend a similar percentage eating hay, if it is available free choice.

Try offering your mare as much roughage as you can. I’d suggest providing more than one type---several kinds of hay, straw or other forage. You can slow down her intake by presenting the hay in a net that has small openings or a feeder designed to slow a horse’s intake. While on pasture she could wear a grazing muzzle to prevent her from ingesting the plastic flags.

I hope you and your husband can keep enjoying this personable mare for many years to come.

Katherine A. Houpt, VMD, PhD, DACVB Animal Behavior Consultants of Northern Michigan Gaylord, Michigan

The behavior called pica is defined as eating non-feed objects.