Most any horse will gnaw on wood now and then, especially trees. An extensive Australian study of wild horses found they had definite preferences in terms of bark texture and time of year. They may eat the more tender, slender ends of tree branches. However, this natural behavior is different from the wood chewing domesticated horses do because wild horses leave tough, woody parts undisturbed.
The belief persists that horses may chew wood because of a mineral deficiency, but this has never been proven. Horses with perfectly balanced diets may still chew wood. No one has proven why horses chew wood, but boredom, being without food for too long, and not getting enough hay/fiber are possible reasons.
When a horse eats, it only takes from four to six hours for the meal to pass through the stomach and small intestine, roughly two hours of that being time in the stomach. To match this digestive pattern, the horse comes equipped with a drive to eat that is nearly constant.
Another often overlooked cause of wood chewing is anxiety. Horses will also often chew wood more when in an unfamiliar situation, if they have a neighbor they dislike or if they have some source of physical distress. We’ve seen this in our test barns, where horses (often the submissive ones) will chew wood when stalled next to some horses, but stop it if they get a new neighbor.
Wood chewing can also be ”contagious.” In group settings, especially, if one horse decides to spend time chewing on fencing, there’s a good chance one or others will join in.
Excessive wood chewing could lead to more wear on the incisor teeth. However, long incisors are common in domesticated horses anyway, so this is rarely an issue. Splinters in the lips, gums or tongue are always possible, but it’s not often recognized as a problem. Wood chewers are also at risk of getting a piece of wood stuck between their teeth or wedged tightly in the back of the throat. Wood is poorly fermentable and could serve as a starting point for enteroliths to form.
The major, immediately obvious impact of wood chewing is on your property. Damage to stalls, fencing, feed boxes, hay mangers and trees not only looks terrible, it’s costly.
Note: Chew-stopping strategies that rely completely on a bad taste won’t work for cribbers because cribbers typically contact the surface only with their teeth. Horses will crib on surfaces treated with anti-chewing products long before they would chew on them. (In an upcoming issue, we’ll discuss products that deter cribbing.)
For the first part of our trial, we used a variety of chew-stopping products both on horses that were chewing wood, and on tails of broodmares and weanlings that were under attack from their foals or pasture mates.
The best results by far were obtained with the two products that had a very obvious unpleasant and somewhat irritating odor: McNasty and RapLast.
RapLast was the more effective of the two in terms of how long it lasted and is so disagreeable you don’t have to cover the entire surface or use a large amount. Direct a stream of the product to spots about four to six inches apart. Do not use a spray setting on the sprayer, use stream. Spray makes small particles which are extremely irritating to eyes and nose.
When using antichew products outdoors, reapplied the product as soon as chewing restarts and after a rain. With indoor use, RapLast effects lasted about a week, longer if the product absorbed deeply into the wood. McNasty lasted several days.
All the products in our trial can also be used to discourage horses from pulling off wraps or chewing on blankets. Because these materials are more absorbent than wood, a single application will last much longer. However, their effectiveness in discouraging these behaviors is virtually identical to the results with wood chewing.
A single treatment with RapLast will last until the blanket gets wet or the wraps are washed. Even the residual effect is so strong that you need to wash your hands after handling wraps that have been treated with RapLast.
RapLast nips McNasty as our first choice to deter wood chewing, although McNasty is the better deal, earning Best Buy. Both are effective deterrents for wood, bandage and blanket chewing. For tail chewing, we like Su-Per Red Hot Spray best.
We recommended Quitt in 2005, and we continue to think it’s worth a try if you’d rather not fool around with sprays, especially with its money-back guarantee.
Horse Journal staff article.