The horse is a great athlete, capable of strenuous exercise over prolonged periods. But all that muscular activity generates heat. This causes an increase in body temperature. Under normal circumstances the horse is able to lose the excess heat and maintain its body temperature within tightly controlled limits.
In response to the release of epinephrine, and the increase in skin temperature, the horse starts to sweat. Evaporation of sweat is the most important means of losi…