Thermoregulation in the horse exercising under hot and humid conditions

Thermoregulation is the homeostatic control of body temperature despite fluctuations due to exercise or ambient variations. The increased muscle metabolism necessitated by exercise is energy inefficient. It results in measurable increases in stored body heat which must be shed in order to maintain exercise at the same intensity. Horses regulate body temperature primarily by evaporation of sweat from the skin surface, but the efficiency of this mechanism is compromised by high ambient humidity. Some minor heat load is lost via respiratory evaporation and convection, mechanisms which are enhanced by increased respirations under hot and humid conditions. Conductive heat loss can be enhanced by application of high volumes of cold water followed by rapid removal (sweat scraping) and reapplication.