Thermoregulation in the Exercising Horse

A byproduct of exercise in the horse is body heat. The more intense the exercise, the more body heat is generated. The more body heat generated, the greater the challenge of removing that excess heat. Horses are large animals with a relatively small surface area to body weight ratio. As a result, they are very inefficient at dissipating heat. The single most important means the horse has for getting rid of this enormous heat load is evaporation, through sweating, which can account for about 65% of the heat dissipation. During workouts such as racing, endurance riding and eventing, the increased muscle work and resulting heat production can account for sweat losses of more than 10 liters/hour. This heat dissipation may be enhanced by air movement over the body (wind). If ambient conditions of high heat, humidity and no wind exist, it can become difficult for a competing horse to cool itself efficiently.

The lungs account for another 25% of heat dissipation. This capacity of the respiratory tract in dissipating heat from the body becomes very important under conditions of high humidity and high temperature when conditions are not favorable for evaporation.

Management techniques play a major role in assisting the horse to safely and quickly lower its body temperature under conditions of exercise in the heat. These include repetitive bathing with cold or ice water, providing cool drinking water and appropriate electrolyte supplements. During rest pauses, horses should be protected from solar radiation by natural shade or shade structures. Misting fans in the shade will decrease the air temperature and provide wind to facilitate cooling. Competitions in hot weather should be held as early in the day as possible when temperatures are lower and solar radiation may be less severe.