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April 12, 2011

Why Do Horses Eat Weird Things?

Curiosity is usually the reason that horses try eating all kinds of odd things. Photo by © Dan65/Fotolia.com.

Horses are not fastidious eaters. I mean, they’re not carnivores, so they will generally turn up their noses at a good steak (although I did run into a horse that had a taste for hot dogs). But they were essentially born to eat. In the wild (which isn’t always the best measure, by the way), they eat in 23 of 24 hours during the day. Eating like a horse, indeed.

Anyway, periodically I get questions about why horses eat what they eat, and whether what they eat is bad for them. Here are some answers.

Many horses are kept in stalls bedded with wood shavings. Wood shavings are absorbent, and smell nice, which, of course, is particularly important for us, since we’re the ones that put them there. (Horses also like to get dirty, and they don’t seem to care much how they smell, which is also perplexing to owners).

Wood shavings are also not unpalatable. Not that you’ll see a lot of horses munching down on their shavings with any regularity, but there are many horses that are more than happy to consume a mouthful of shavings just so they can savor that last alfalfa leaf. The practice is completely harmless, unless you’re using black walnut shavings. Those are fairly toxic to horses; they cause severe laminitis, a problem that, sadly, took a few horses getting really sick to recognize, a few years back. Chances are you aren’t going to find any black walnut shavings in your horse’s stall, and, if you do, get him, or them, out.

Wood is, in fact, a good fiber source. Horses that are fiber deficient (a mostly experimental condition, but possible in horses kept only on lush grass with no access to coarser forage) will look for fiber sources, such as wood. Again, it probably won’t hurt them, although horses that insist on eating wood (planks, fences, doors, etc.) are a big pain in the backside: sort of like having an oversized pet beaver. If you’re feeding your horse hay, then he’s getting enough fiber. If he’s eating wood anyway, he’s probably bored.

Horses eat manure, too. The practice is called coprophagy. (I have to throw in big words from time to time­—it’s what I went to school for). That’s also a practice that’s pretty harmless and pretty widespread.

Young elephants, koalas, hippopotami (I love that plural), and pandas are among animals—including horses—whose young eat feces, which is thought to help populate their intestines with the bacteria that help allow them to digest the coarse feed that they live on.

It’s Nutritious!

Rabbits, guinea pigs and chinchillas eat their own feces, which are actually thought to be quite nutritious. So, for that matter is horse manure, which has some undigested plant material in it. Dogs eat horse manure (which is just one of many reasons why I don’t like barn dogs to lick me in the face); apes have been seen eating horse manure, presumably for the salt. It even used to be fairly common to feed horse manure to pigs. Flies, of course, love manure. Think of it this way: If you’re raising a horse, you’re going to be raising flies, too.

While eating horse manure is generally harmless (and, apparently, tasty), it is one way that internal parasites are transmitted. People with pastured horses that insist on spreading manure in their fields only compound the problem of parasite transmission. But in horses that are kept in stalls, with limited access to pasture, the occasional bite of manure is harmless. The phrase, “An apple a day keeps the doctor away,” was not, however, written about horse droppings.

The practice of eating other weird things (dirt, hair, rocks, etc.) is called pica. It seems that lots of people get really worked up about it. There’s this idea out there that horses have some sort of “innate intelligence” about their diet. That is, if they are missing some micronutrient, or have some sort of a vitamin to mineral imbalance, they will try to fix the problem on their own.

This Old Wives’ Tale Is Wrong

That seems not to be the case. Equine nutritionists, who, in addition to be very good at basic math, study such things, have found that horses really only seek out energy (calories—hungry horses, like hungry people, seek out something to eat), water, salt and fiber. Horses that have nutritional imbalances typically don’t eat dirt, or other weird things, like concrete, or anything else. Such behaviors reflect curiosity, not nutritional problems.

There’s even research to support the idea that horses with dietary deficiencies don’t seek to correct them. (I really like it when there’s research to answer questions.) In the 1970s ponies were fed diets that were deficient in calcium. Those ponies didn’t eat any more of a calcium-containing supplement than did ponies that had adequate calcium in their diets. In another research study, ponies fed a diet lacking phosphorus were given access to several different mineral salts, including those containing phosphorus. Those ponies—not nutritionally wise, apparently—actually ate more calcium, which, theoretically, would have made any mineral imbalance worse, since eating more calcium interferes with phosphorus absorption.

That said, there was a study last year, from Turkey (I like to read) that looked at 15 horses, who either did, or did not, engage in pica. They ran blood tests on the horses and concluded that the horses with pica had lower levels of copper and iron in their blood, as well as the mathematical ratio of copper to zinc. Frankly, I don’t really get the study, because it seems to me that if they were eating weird things to correct an imbalance, they wouldn’t have had the imbalance, but that’s just me. Suffice it to say that in the absence of more rigorous studies, I generally don’t think that pica is a big deal for horses, healthwise.

Of course, eating sand is another matter entirely. In areas that have a lot of sand, such as Florida, Nebraska, Arizona or southern California, sand colic is a problem. These horses, however, eat sand along with their feed, and some of them can accumulate so much sand (I’ve seen 70 pounds of sand in a horse’s gut in surgery) that it blocks the intestines. They aren’t eating sand because of some dietary problem—it just comes along with whatever else they are trying to eat.

Anyway, mostly, when horses eat weird things, it’s not a big deal. Horses are curious, and, like young kids, they put their mouths on most anything. As long as what they’re eating isn’t directly harmful to them (say, oleander leaves or feed bags), eating weird things is more annoying, and sometimes destructive, than anything else. If your horse is happy munching on a mouthful of shavings, then I say, “Good for him.” Happy is a good place to be.

David W. Ramey, DVM, began veterinary practice in 1984 in the Los Angeles area of southern California, and he is still there today. His clinical practice specializes in the care and treatment of sport and pleasure horses. Dr. Ramey is a vocal advocate for the application of science to medicine, and, as such, for the welfare of the horse. He is an internationally known author and lecturer, and he's written more than a dozen books on a variety of horse care topics. He's also presented topics at the American Association of Equine Practitioners meeting seven times, most recently in 2008. To learn more about Dr. Ramey, visit http://www.doctorramey.com/.

The opinions expressed by www.chronofhorse.com columnists are entirely their own and not necessarily those of The Chronicle of the Horse. Always consult with your own veterinarian before undertaking any course of treatment for your animal or changing treatments or medications your veterinarian has already prescribed.

 

 

 

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