In addition to humans, horses are one of the few animal species that use sweating as the primary means for dissipating heat. Sweating is an example of evaporative cooling and accounts for over 50% of heat loss in the horse. Sweat not only contains water, it also contains electrolytes, certain minerals and a protein called latherin. Latherin imparts the “foam” in heavily sweating horses and contributes to the evaporative efficiency. Wiping sweat or lather off the horse is counterproductive, as it will decrease the evaporative cooling effect.
The importance of electrolyte replacement cannot be overemphasized. Water and electrolytes cannot be stockpiled; they must be replenished, preferably as they are lost or shortly thereafter.