How do horses primarily cool themselves?

Horses primarily cool themselves through evaporative heat loss via sweating. When a horse begins to heat up from exercise or high temperatures, its body activates sweat glands, producing sweat that evaporates off the skin. This process absorbs heat from the horse's body, effectively lowering its temperature. Unlike humans, horses have a unique sweat composition that includes proteins called latherin, which helps the sweat spread evenly over the skin and enhance evaporation.

While other methods of cooling can play a role in a horse's overall thermoregulation—such as resting in the shade or using their respiratory system to some extent—the primary and most effective means is through the sweating process. Rapid heart rate reduction is related more to recovery than cooling, and while seeking shade does help, it does not represent a physiological method of cooling like sweating does.