The efficacy of capsaicin as an equine repellent for chewing wood

Capsaicin, a component of chili peppers, is a natural repellent for many mammals because of it being an irritant to the nasal and oral areas. We tested whether topical application of capsaicin in a commercially available product caused aversion to licking and chewing of wood by horses and hence might potentially prevent crib biting. Ten non–wood-chewing horses underwent 3 sequential trials involving the presentation of different treatments applied to a clean piece of wood (wooden block). Initially horses were exposed to molasses only, followed by equal proportions of molasses and the capsaicin product (Equi-Stop), and then a return to molasses only. The addition of capsaicin to molasses caused a significant reduction in the frequency of licking or chewing of a standardized wooden block and was associated with significant increases in behaviors that may be associated with equine irritation, including rubbing and head shaking, plus the nasal investigative behavior of flehmen response. The combination of both the reduction of licking or chewing of the wooden block and the increase in irritation and nasal investigation behaviors suggests that capsaicin may be an effective repellent for horses chewing wood. The significantly lower licking or chewing rates of wooden blocks coated with molasses only at the end of the trial sequence compared to that at the start suggests a learned aversion after exposure to capsaicin at least in some horses. This capsaicin-based product has the potential as a management tool for reducing the incidence of wood chewing and possibly crib biting in horses.