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When horses become TERMITES
Understanding wood chewing and cribbing behaviors in horses
Floridians are well aware that termites are capable of causing significant economic and physical damage to wooden structures. These little insects are unique in that they thrive virtually exclusively on wood. While some horses also seem to have a termite gene and try to "eat the barn down around them," horses are not capable of thriving on wood. Termites produce an enzyme, cellulase, that breaks down the poorly digestible wood component, cellulose. They also have microorganisms in their digestive system that are capable of digesting cellulose. Horses do not produce cellulase themselves, but are able to digest plant material with help from microbes in their digestive system. The horse's system is pretty good at digesting the more digestible fibers of grass but can't do much with the high cellulose content of wood. That doesn't seem to keep some horses from giving it a good try.
Wood chewing is seen in both confined and pastured horses and may be a highly individual behavior. It has been reported that two-to-three horses out of a group of 10 did 90 percent of the wood chewing. Chewing wood is more common during cold and wet weather, when diets are low in fiber or high in grain content, when horses are confined and bored or in young horses soon after weaning. In weanlings, this may be a behavior similar to teething in children. As their teeth erupt and they are no longer nursing, chewing wood may help alleviate some pain from new teeth coming in.
Horses rapidly changed from long-stemmed hay to a completely pelleted ration, replacing the grain and hay, may be more likely to chew wood because they eat the pelleted ration more quickly. This creates more time for boredom to set in. Horses gradually changed to a completely pelleted ration offered in smaller, more frequent meals adjust quite readily to this type of diet.
Chewing tree bark has been reported to be common in feral horses. These free-roaming horses often browse on brush, leaves and tree bark even when there is ample grass available. If horses have free access to trees, they can chew enough bark to kill a tree in a short period of time. Some trees are potentially toxic to horses, including cherry, peach, black walnut, black locust and certain types of pine. For the safety of the trees and the horses, measures should be taken to prevent horses from chewing on tree bark.
The relatively regular occurrence of wood chewing in horses indicates that this oral behavior may be a normal foraging behavior in horses and not a stable vice. Most often, wood chewing has an economic impact due to damage to barns, trees and fences rather than causing any health problems for the horse, although wood splinters have been reported to cause small intestinal obstruction in some horses. Some cases of wood chewing may be related to a diet low in fiber or to boredom, but many cases are horses just looking for something different to chew or taste.
Chewing Vs. Cribbing
Horse owners may be concerned that wood chewing could lead to cribbing, but these are very different behaviors and one doesnŐt seem to lead to the other. Cribbing behavior is included in the list of stable vices or stereotypies. These are defined as apparently functionless, repetitive behaviors. True cribbers set their incisors (front teeth) over a stationary object such as a fence board or edge of a feed trough, arch their necks and pull back. They often emit a grunting sound which is thought to be "sucking" air but some say they are actually forcing air out, similar to a burp. Cribbing is thought to be more prevalent in nervous, high-strung horses confined to a stall and in horses eating high amounts of concentrate feed. Some reports correlate cribbing with stomach acidity and gastric ulcers. However, there are many accounts of pastured horses cribbing, so there may be additional factors involved. Cribbing has been reported to be found in much higher numbers in some families of Thoroughbreds, indicating a possible hereditary predisposition to this behavior.
The Bottom Line?
Even though both wood chewing and cribbing are seen in pastured horses, confinement and stress both seem to increase the risk of these behaviors. Feeding plenty of fiber, providing ample turnout and exercise and letting horses see out of their stalls are all possible management options to help reduce the occurrence of these unwanted behaviors. Playing music in the barn could also help lower the stress level in the barn.
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(c) 2007 Horse Capital Digest.com |
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