Horses and humans share an ability to sweat excessively which is rare amongst other mammals
Human sweat glands are mostly eccrine producing a hypotonic (high sodium) clear fluid through the pores
Horse sweat glands are mostly apocrine producing a protein rich (Latherin) and electrolyte fluid via a duct through to the hair follicle
Latherin is also found in the saliva of horses and other mammals to aid lubrication whilst chewing a fibrous diet
The presence of latherin in the skin is exclusive to Equids. It contributes to rapidly and effectively dissipating heat during periods of intense or prolonged exercise
Latherin in horse sweat acts like a detergent to efficiently drench the horses water-proof coat, allowing evaporation to occur
Latherin becomes white and foamy with friction - just like when you lather up a sponge with soap - This is why horses get a white sweat under tack or between their legs or a white foam in their mouth when they chew food or the bit
Sweating accounts for around 70% of thermoregulation in the horse
Horses can develop an inability to sweat - Anhidrosis. A dangerous condition, more commonly seen in horses living in hot humid climates where the environment means evaporation is ineffective. Treatment is limited, but in some cases, moving to a cooler climate allows the horse to better thermoregulate and the ability to sweat returns
Did you know Horse breeds with a higher tolerance for exercise are more likely to have a higher concentration of apocrine glands to aid thermoregulation. It’s why Thoroughbreds are often seen getting a sweat on before natives
The amount of sweat during exercise doesn’t necessarily indicate the level of fitness or intensity of exercise - environment, body composition, aerobic capacity and recovery rates are far more reliable indicators
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