Knowing how your horse thermo-regulates will help you better understand how to keep him cool. A horse's body produces heat when he works. Horses have several mechanisms that get rid of this heat.
The most important mechanism is evaporation. Most heat is generated from a horse's large muscle mass. The cardiovascular system (the heart and blood vessels) move the heat from the muscles and organs to the skin. As your horse works, he produces sweat in glands in his skin. This sweat is composed of water and electrolytes (sodium, chloride, potassium, and calcium). As the sweat evaporates, it dissipates large amounts of heat, thus cooling your horse. To give you an idea of how much a horse needs to sweat to keep cool, the amount of heat dissipated by one liter of sweat equals just one to two minutes of maximal exercise, or five to six minutes of sub maximal exercise!
