Physiological and behavioral consequences associated with short-term prevention of crib-biting in horses.

The research explores the effects of preventing crib-biting in horses, a common stress-relieving behavioral issue. It examines the changes in behavior, heart rate and hormonal levels in normal and crib-biting horses.

Introduction and Methods

• The study was conducted on twelve horses, six of which were regular crib-biters, and six were normal healthy horses. Crib-biting is a behavioral trait in horses where they chew or bite on non-food materials. This is often seen as a stress-reducing activity that is usually prevented by horse owners via physical means.
• The researchers undertook a series of tests to observe changes in behavior, heart rate, and plasma cortisol and beta-endorphin concentrations in both normal and crib-biting horses. Cortisol is a hormone that is released during stress, and beta-endorphin is a peptide that produces a sense of well-being.

Behavioral Changes

• The study found that when crib-biting horses were prevented from displaying this behavior, they showed an increase in ingestive behavior or eating. This points to the role of crib-biting as a coping mechanism.
• Interestingly, when these horses were simultaneously prevented from crib-biting and eating, their foregut’s motility, or the ability to move food through the digestive system, experienced stagnation. This suggests that the normal gut function in these horses relies on unrestricted access to food and potential objects to crib-bite.

Hormonal Levels

• Regarding hormonal levels, the study found that there was no significant difference in the mean baseline levels between normal and crib-biting horses. However, against initial expectations, beta-endorphin levels were found to be higher in crib-biting horses than in normal ones when they were prevented from crib-biting. This could indicate that the feeling of well-being experienced by the horses may increase when prevented from crib-biting, which seems counterintuitive.
• Baseline cortisol levels in crib-biting horses were found to be higher than those in normal horses under various conditions, suggesting that crib-biting horses may experience higher levels of stress. The absence of a significant rise in cortisol levels in crib-biters during periods when crib-biting was prevented suggests that the function of this behavior might not be stress reduction, despite popular belief.