Horses exercising in the heat quickly develop high body temperatures. The overheating can become life-threatening if they don’t have efficient ways of dissipating the heat.
There are several ways heat leaves the body:
- Radiation: This is transfer of heat energy to the air surrounding it. Veins in the skin dilate during exercise, bringing more hot blood to the surface.
- Conduction: Transfer of heat to a solid or liquid in contact with the body.
- Convection: Moving air crossing the body picks up heat and removes it (e.g. a fan or breeze)
- Evaporation: Water/sweat on the surface of the body is heated then evaporates. Sweating is responsible for 85% of the heat loss during exercise.
The horse produces from 1 to 4 gallons of sweat per hour when exercising, and more in the cool down period after exercise. The first requirement for keeping this cooling mechanism going is plenty of water. The production of sweat is triggered by release of epinephrine. The release of sweat also involves purinergic receptors which are activated by either adenosine or its products – ATP, ADP, UDP. Once activated, calcium ions are released and sweat production begins.
Making sweat also requires a steady supply of electrolytes – sodium (Na), potassium (K) and chloride (Cl). Start with a generous amount of hay or pasture (for K and Cl) plus 2 oz of plain salt/day (Na, Cl). For horses sweating heavily or working more than 2 hours, add a properly balanced electrolyte. Always match electrolyte supplementation to the horse’s sweating. Giving too much can actually worsen dehydration.
As important as electrolytes are to sweating, you cannot increase sweating by feeding more electrolytes. Many things have been tried to support good sweating in horses and about the only universal truth is that nothing works all the time, or even most of the time. I have had the best results with a combination of 1 scoop each of L-leucine (9.85 grams) and Jiaogulan (7 grams) twice a day.
The protein in sweat, latherin, is almost 25% leucine. Jiaogulan is an adaptogenic herb. Adaptogens help maintain a normal and balanced output of stress hormones, including epinephrine.
Efficient sweating is your key to maintaining performance and preserving health in the heat. Do your best to support it.
Eleanor Kellon, VMD