It’s summer and the temperatures are over 100 degrees in many parts of the country. These temperatures can have an effect on horses as well as humans.  It is important to know when horses are at risk for heat stress and today we are going to talk about some information on heat stress published by the Kentucky Equine Research staff. The most common method of predicting heat stress is to take the outside air temperature and add that number to the percent humidity. If the sum of these numbers is less than 130, the chance of heat stress is unlikely.  If the sum is over 150, the horse’s ability to lose body heat is severely decreased, especially if humidity is greater than 50% of the total.  If the sum of the temperature and humidity is greater than 170, the horse can lose little body heat and should probably not be worked in this environment. 

Horses lose body heat through sweat, exhaling warm air, and widening blood vessels in the skin.  When the air temperature is near body temperature, heat loss is greatly decreased.  About 30% of increased body heat is lost in sweat as horses working in hot humid conditions can lose over 7 gallons of fluid as sweat, in addition to electrolytes important for body function.  Loosing 7 gallons an hour will certainly cause dehydration so horses working in this heat must drink plenty of water and should be given electrolytes.  It is important to monitor your horse’s temperature. A horse’s normal temperature can get to 103 degrees Fahrenheit with exercise but if it gets over 105F, you should be concerned. So if the air temperature and humidity added together are more than 150, it may be too hot for your horse to go riding.