Potential roles of Selenium and Zinc in the pathophysiology of crib-biting behavior in horses

Crib-biting is repetitive and compulsive behavior that characterized by “grasping a fixed object with incisor teeth and aspirating air with an audible grunt”. Little is known about etiology and pathophysiology of crib-biting behavior in horses. Previously we have shown that oxidative stress is linked to crib-biting, with crib biters showing lower antioxidant capacity than non-crib-biting horses. The aim of the present study was extend our understanding of oxidative stress in crib-biting to determine the serum contents of some mineral trace elements (manganese (Mn), magnesium (Mg), selenium (Se), copper (Cu), and zinc (Zn)), and electrolytes (sodium (Na), potassium (K), calcium (Ca) and phosphorus (P)). Also, activity of enzymes (ALT, AST, ALP and GGT), some hormones (Ccortisol, ghrelin, β-endorphin and serotonin) and blood biochemistry values of various parameters were measured to evaluate their possible association with crib-biting behavior in horses. Blood samples were taken from all horses under the following conditions: basal conditions of crib biting horses, during or immediately after crib-biting periods, and from non-crib biting, healthy horses (control group). Serum Se concentration was significantly lower (P≤0.001) in crib biting horses than in controls, with the lowest levels seen during crib-biting behavior. Other measured parameters did not differ between acute crib biting horses and healthy controls. These observations suggest that alterations in serum Se, an important component of the antioxidant system, may play a role in the pathophysiology of crib-biting behavior in horses, adding further evidence to the theory that crib-biting may be related to increased oxidative stress and alterations in essential trace elements.