The Harry M. Zweig Memorial Fund for Equine Research

Effects of Iso-Caloric Diets Differing in Sweetness or Lactic Acid Production on Cribbing

Dr. Katherine A. Houpt

Cribbing is a behavioral abnormality that affects approximately 300,000 horses in the United States. Cribbing is the behavior in which a horse grasps a horizontal surface with its teeth, flexes its neck, and pulls back. The sound of cribbing is caused by aspiration of air into the esophagus. Little of the air is swallowed, and few horses actually develop colic, but owners dislike cribbing because of the damage caused to fences and buckets when the horse pulls them while cribbing. Some owners dislike the sound. Wood chewing is a different behavior in which wood is actually chewed and swallowed. We believe that cribbing may be caused by perception of sweet taste, which leads to opiate release, which in turns leads to cribbing. Another possibility which we wish to test is that cribbing is a response to pain resulting from acidic conditions in the large intestine. Acid in the large intestine may lead to pain, which leads to opiate release, which leads to cribbing.

Various devices from muzzles to collars and including shock collars have been used in unsuccessful attempts to prevent the behavior. Some of these devices (in particular the tight fitting collars) cause tissue damage and others (the shock collars) cause pain to the horses. It would be more beneficial to the horse to determine the reason it is cribbing and remove that stimulus rather than punishing it.

The primary long-term goal of this study is to develop an effective management method to prevent cribbing or to treat horses that have already developed the problem behavior. The method should not involve pain or frustration to the horse—yet allow it to consume a high performance diet. The most practical treatment is a change in diet or a feed additive that will reduce or eliminate cribbing. We have developed diets that block the sweet taste of the grain/molasses mixtures which are the typical high performance horse diet. Another diet replaces 50% of the carbohydrate calories with fat so that the horse can perform at a high level but does not have as much sweet feed. There is an antibiotic, virginiamycin, which inhibits the acid producing bacteria in the large intestine of the horse. This will be added to the high concentrate diet. We wish to test each of these three diets to determine which is most effective in reducing cribbing. Each diet will be fed for 3 weeks to determine the long term effect on cribbing. Cribbing rate will be measured by time-lapse videorecording. There will be a 3-week transition period to adapt the horses to each new diet.