Thermoregulation. Base mechanisms and hyperthermia.

Metabolic HP is extremely high during exercise in horses. Thermoregulation in horses is primarily dependent on evaporative heat loss from sweating in particular. Under thermoneutral conditions, these mechanisms are sufficient to allow horses to perform high-intensity exercise for long periods. Under thermally stressful conditions, particularly in high ambient humidity, the efficiency of evaporative heat loss mechanisms is compromised and may result in horses developing hyperthermia. Early recognition and vigorous treatment are essential to limit the consequences of heat stress in horses. Meticulous planning and management of equestrian events that are held under thermally stressful conditions are essential to ensure the welfare of competing horses and their riders. The conditioning program of horses expected to compete under thermally stressful conditions must also make adequate provision for acclimatization to the hot, humid conditions.