Original Article: Horsetalk.co.nz
Horses and humans use the same strategies for keeping cool, but there the similarities end.
Horses are nowhere near as efficient as people in staying cool. It's all because of their body shape and their much greater percentage of heat-generating muscle.
The difference is most apparent in hot and humid conditions, when a horse's rate of heat build-up will be about three and a half times greater than that of a human.
"For us as caregivers to horses, it is critically important to recognise these very high rates of heat storage," says Dr Michael Lindinger, from the Department of Human Health and Nutritional Science at the University of Guelph, in Ontario, Canada.
"Even though we may perceive that warm, humid conditions are not producing undue stress or strain in us, they may certainly be resulting in strain in horses," he says.
The higher rates of heat storage in horses result from a greater proportion of contracting muscle in horses - some 40% of body mass - compared to about 20% in running humans.
Also, horses have a lower skin surface in relation to their size than people, meaning their ability to dissipate heat is greatly reduced compared to humans. Horses have only 40% of the surface area to body mass as people do.
"Horses are capable of producing large amounts of heat at high rates but, compared to humans, are a severe physical disadvantage in dissipating that heat."
Lindinger, whose particular interests lie in the regulation of ion transport across cell membranes and the regulation of body fluid balance, was amongst speakers at the fourth European Equine Health and Nutrition Congress in the Netherlands, where he talked about challenges faced by performance horses in staying cool.