Summer's heat and humidity can be much more than just uncomfortable. They can be deadly. Horses lose their lives every year to heat stroke. Countless others struggle through anything from weakness to colic as a result of inadequate care in hot weather. Don't let this happen to your horse!
Your horse's normal body temperature is 98.5 to 101 degrees Fahrenheit. His body temperature rises as he exerts himself. To avoid reaching temperatures that can damage his brain and organs, he must be able to get rid of that heat.
Your horse has several ways to stay cool. Some of the heat is transferred to the air exiting his lungs. The remainder is carried to the skin surface by the bloodstream. Blood vessels very close to the surface of the skin dilate, and dissipate heat through conduction, convection, and evaporation.
Conduction is the transfer of heat from the body to the cooler air.
Convection is the movement of hot air away from the body's surface, replacing it with cooler air.
Evaporation of sweat is absolutely necessary for efficient heat removal.
Cool Your Hot Horse
Here are six ways you cool your horse as the temperature rises.
Create a breeze. Slow walking creates a bit of a breeze over your horse's body surface to enhance convective cooling. A fan works even better!
Find cooler air. Shade provides cooler air temperatures, which also enhances convective cooling.
Hose him down. As you hose off your horse, heat is lost due to evaporative cooling. Heat is also lost by conduction, as long as the water temperature is cooler than his body surface.
Myth alert! Note that hosing your hot horse down with cold water doesn't cause any ill effects. The colder the water, the more conduction heat loss occurs.
Use misting fans. Using misting fans is the most efficient method of all methods. In fact, Olympic horses are kept cool with this method. The mist causes cooling by conduction and evaporation, while the fans' breeze improves both evaporation and convection.
Offer water. Allowing your hot horse to drink also has cooling effects, as the water temperature and your horse's interior temperature equalize. Of course, water also helps to keep him hydrated. Severe dehydration can lead to organ damage. Myth alert! There are no health risks associated with letting a hot horse drink cold water. And there's no such thing as giving your horse "too much" water.
Add electrolytes. Your exercising horse loses electrolytes along with water in his sweat. His cells function like small batteries with different concentrations of electrolytes inside versus outside the cell. There are even differences in concentrations between the structures inside the cells.
Another function of electrolytes, especially sodium, is to "hold" water in your horse's body. To maintain proper hydration levels, his brain constantly monitors sodium concentration. Thirst is triggered if the concentration of sodium gets too high; salt hunger is triggered if sodium gets too low. (For how to safely replace electrolytes, click here.)
There's a place for electrolyte supplements, but they have to be used correctly. Use this checklist to get started.
[ ] Use plain salt to meet your horse's baseline sodium and chloride needs. Give him 1 ounce per day in winter, 2 ounces per day in summer.
[ ] If your horse is working two hours or less at low sweating rates, or one hour or less at moderate sweating rates, add 1 extra ounce of salt for each hour of low sweating work, 2 ounces for each hour of moderate sweating.
[ ] If your horse is working longer than the times above, feed the extra salt only to meet the needs of the first two hours (or the one hour of moderate sweating), then use an electrolyte replacement for any additional work above that level.
[ ] Crucial! Give your horse as much water as he wants, as often as he wants it!
Eleanor M. Kellon, VMD, currently works as a writer, teacher, and internal medicine/nutrition consultant. Prior to this, Dr. Kellon has had more than 10 years experience in private practice. She also has extensive experience with performance horses. She's based in Pennsylvania, where she and her husband raise, train, and race Standardbreds. Her most recent book is Horse Journal Guide to Equine Supplements and Nutraceuticals (Globe Pequot Press).