Cribbing, not to be confused with simple wood chewing, is a stereotypical behavior in horses, in which the horse places its upper front teeth on an object and applies down pressure. As it does so, the horse makes a belching sound, then relaxes for a few seconds, before doing it all again. The primary theory behind cribbing, is that the action of applying pressure with the front teeth allows the horse to suck in a gulp of air, which somehow causes the release of endorphins in the horses system, causing a pleasurable sensation. In other words, it’s an addiction. It is considered an unsoundness in horses and causes the buildup of the lower neck muscles in some horses, which can be somewhat unattractive.

Cribbing has also been linked to other equine ailments, such as stomach ulcers, colic, flatulence,  and other nervous obsessive behaviors.

Treatments for cribbing, over the years, none of which has enjoyed any consistent degree of success, involves everything from simply giving the horse more pasture time, to the wearing of restrictive cribbing collars, and even surgery to cut certain nerves and muscles in the neck to make the horse unable to crib.

Interestingly, as I have read various articles about cribbing, I only found one reference to any scientific data regarding the behavior.  Tufts University School of Veterinary Medicine, Boston, MA, a number of years ago, experimented with injecting horses with a drug that blocks endorphins in the horse’s system. They saw a marked decrease in the horses’ cribbing while the drug was actively being administered, however the horses returned to cribbing once it wore off. That is the single reference of any kind I was able to come up with in support of the endorphin addiction theory, despite the fact that this theory has been considered doctrinal in veterinary medicine for years.

I recently came across the abstract from a paper on cribbing that indicated the belching sound one hears as a horse cribs, may be an actual belch. The study said that evidence had been produced to indicate that feeding highly concentrated feed, such as grain or sweet feed, may cause some horses to experience gastric discomfort, and that the act of cribbing may actually allow the horse to belch and release gas pressure inside the stomach, or it may stimulate the salivary glands, sending saliva into the stomach to bring relief. I could not find the link for the study again to post it.

In light of this study, it makes sense that cribbing would be associated with ailments such as ulcers, colic, and flatulence, not as a result of the cribbing, but as a result of the gastric distress caused by a sensitivity to the feed. I found an article here from the ASPCA, that discusses cribbing in more detail and more authoritatively than I can.

A horse I help care for is a chronic cribber. He’s 21 years old and has been cribbing pretty much all his life. He has lived with a cribbing collar much of his life. His front teeth are worn short. He has selected a section of steel pipe fence as his favorite cribbing tool and has actually bent the pipe flat where he cribs. While cribbing he becomes so intent on what he is doing that it is hard to drive him away from the pipe fence section, and as soon as he can get around me, he goes right back to it. In the picture, you can see he is cribbing with full force, despite his tightly fitted cribbing collar.

Not long after I read the above-referenced abstract, we had a cold snap here in Virginia. I told the owners of the horse, whose son is responsible for feeding the horses, to start feeding a couple quarts of “sweet feed” (a grain feed with molasses mixed in) in the evenings, along with their normal ration of hay, to help them deal with the cold. A few days later I went by to check on the horses and found this particular horse at the pipe fence cribbing. It suddenly dawned on me that I hadn’t seen him cribbing for many months, until then. I contacted the owners and suggested we increase the horses’ ration of hay and stop feeding the grain. I went by this past week to ride my horse and check on the other. He was calmly grazing out in the pasture.

He came up to the barn as I brushed and readied my horse for the ride. I removed his cribbing collar and tossed him a couple flakes of hay (orchard grass). I took my horse out for a 2-hour ride. When I returned, the horse was again calmly grazing in the pasture. As I unsaddled and worked on my horse for a few minutes, I watched the cribber. He walked up to his favorite pipe fence section and placed his mouth on the fence, as he normally does when he cribs, but only tried it once or twice and quit, neither did he do it with the strength he normally does (which bent the steel pipe fence), then he went right back to grazing. It appeared he tried the cribbing out of habit, rather than out of an addictive need.

From my own experience, I think I can safely say that for this particular horse, the endorphin addiction, if any exists, is less the cause of his cribbing than an upset stomach from feed that is too rich for him. Just as there are people who have sensitivities to milk, eggs, and other things that most of us enjoy, it makes sense to me that some horses may have similar intolerances to certain feeds. For this particular horse, it appears that grains and sweet feed cause him sufficient discomfort that he cribs to relieve it. When he is fed orchard grass hay he does not crib, or better said, he only does it occasionally, apparently out of old habit.

While my findings are neither scientific nor conclusive, at the very least it appears to me there may be sufficient reason to question current theories regarding chronic cribbing and to warrant further scientific study.

Here is a video of this particular horse cribbing:

http://www.youtube.com/my_videos_edit?ns=1&video_id=BTV6OalpscY