Knowing how your horse thermo-regulates will help you better understand how to keep him cool. Horses’ bodies produce heat when they work. They have several mechanisms that get rid of this heat.
The most important mechanism is evaporation. Most heat is generated from a horse’s large muscle mass. The cardiovascular system (the heart and blood vessels) move the heat from the muscles and organs to the skin. As your horse works, he produces sweat in glands in his skin. This sweat is composed of water and electrolytes (sodium, chloride, potassium, and calcium). As the sweat evaporates, it dissipates large amounts of heat, thus cooling your horse. To give you an idea of how much a horse needs to sweat to keep cool, the amount of heat dissipated by one liter of sweat equals just one to two minutes of maximal exercise, or five to six minutes of sub maximal exercise!
Other mechanisms include breathing out some of the heat through respiration. As your horse exercises, his respiration increases, thus releasing heat. Additionally, some heat is lost through convection/radiation where heat is moved directly from the skin to the environment.
Keeping these mechanisms in mind, there are several things you can do to help your equine partner stay cool:
Sometimes we can’t avoid the heat. On those days, keep an eye on the Heat Stress Index. The Heat Stress Index is the sum of the temperature plus the humidity. For example: if the temperature is 80 degrees Fahrenheit and the humidity is 20%, then the Heat Stress Index is 100 (80+20=100). If the Heat Stress Index is less than 120, it is OK to ride. Start watching it if it rises above 120, at 150 your horse’s cooling system won’t work effectively. If it is greater than 180, your horse will be unable to thermo-regulate.
Registered 2011 by Equestrian Collections
Author: Sallie S. Hyman, VMD, DACVIM, CVA
Information in this article is for educational purposes only and is not a substitute for evaluation by an equine professional. In particular, all horse owners should seek advice and treatment from a licensed veterinarian, such as TEVA, for their horses' medical care.
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