Sweating horses 101
Anhidrosis, an inability to sweat, severely compromises performance horses.


Horses are one of the few mammals that have a large number of sweat glands to keep cool. Proper perspiration is essential for performance horses – it keeps them from overheating and helps you monitor their hydration. Here’s everything you need to know about horses and sweat:

How sweating keeps horses cool
Your equine’s muscles generate heat as they work, elevating its normal resting body temperature above 99-100 degrees Fahrenheit. As blood circulates throughout the body, it carries some of this heat to the lungs and also to the skin. Heat in the lungs is exhaled out, while that in the skin convects into the air. As the muscles work harder and produce more heat, radiant cooling and breathing alone become insufficient for regulating the horse’s temperature. The equine’s sweat glands then kick in, producing perspiration that removes heat from the skin as it evaporates.

Horses sweat far more than humans – according to Practical Horseman, they generate twice the amount of sweat per square inch. The surrounding environment then plays a role in how that sweat forms. On dry, hot days, the moisture evaporates almost as quickly as your horse produces it, meaning it could be losing large amounts of fluid without you even noticing. On the other hand, humid climates make it harder for sweat to evaporate, meaning your horse doesn’t cool properly and could suffer heatstroke.

Since the heat is generated internally, horses still sweat when exercising in winter. Instead of evaporating, however, the sweat cools against the horse’s skin, reducing its body temperature. This becomes dangerous once the horse is stationary and its muscles are no longer producing heat. To keep your horse from getting chilled, dry it off with a wool or polar fleece cooler before stabling. These materials naturally draw moisture away while keeping the equine’s body heat trapped underneath. You can also clip you horse’s coat so sweat evaporates easier. Just be sure to dry and blanket the animal before returning it to the stable.

What’s in a horse’s sweat?
As with humans, an equine’s perspiration consists of water, electrolytes, and other components. However, horse sweat has a greater concentration of electrolytes, meaning a large amount of electrolytes are lost when horses exercise and compete.

Horse sweat also contains a protein called latherin, named for the foamy effect it creates. According to research from the University of Glasgow’s Department of Ecology and Evolutionary Biology, latherin reduces the sweat’s surface tension helping it evaporate. The protein causes sweat to foam in areas of contact such as between the thighs and where tack rubs the coat, according to Kentucky Equine Research.

“The factors influencing the production of latherin in horses are unknown,” Peter Huntington, director of nutrition at KER Australia, said. “Popular opinions include lack of fitness and an excess of protein in the diet, but a definitive answer remains elusive.”

When horses can’t sweat
The term anhidrosis describes an inability to produce a proper amount of sweat. While the cause of anhidrosis is unclear, some believe excess production of stress hormones overstimulate​s the horse’s sweat glands, the Hagyard Equine Medical Institute noted. Anhidrosis mostly affects performance horses and those with dark coats, and its effects range from a slight drop in sweat production to hyperthermia or heat stroke.

To diagnose anhidrosis, your veterinarian may inject diluted terbutaline to stimulate the sweat glands. Your vet might also conduct blood work and evaluate the equine’s electrolyte levels. There are many treatment options including medication, supplementation, and environmental changes. However, anhidrosis can’t be cured, only managed for the duration of a horse’s life.



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