PREVENTING HYPERTHERMIA
IN HORSES

Dr. Cynthia McCall
Extension Horse Specialist
Alabama Cooperative Extension System

     The high heat and dry weather of this summer has many horse owners worrying about the effect of this type of weather on their animals. In general, most horses easily adjust to conditions of high heat and humidity, and hyperthermia (heat exhaustion and heatstroke) is not a common problem in the horse.

     Symptoms of heat exhaustion in the horse are weakness, rapid breathing (the horse’s respiration rate may be higher than its heart rate or the horse may be panting), quivering muscles and collapse. The body temperature may be elevated to 105 – 108 o F, and the horse sweats heavily. Heat exhaustion may occur at any time – during light or heavy work, a few hours after work, or when the horse has not been worked at all. The onset of heat exhaustion often is very gradual.

     Heatstroke is a more serious problem where the onset of the problem and the eventual collapse of the horse occur more rapidly than in heat exhaustion. Heatstroke also differs from heat exhaustion in that the horse’s body temperature gets much higher (up to 115 o F), the horse may get a vacant, staring expression in its eyes, and the horse stops sweating. During heatstroke, a horse, which has been sweating, rapidly develops a dry coat in which the hairs stand on end. This indicates a severe breakdown of the body’s cooling mechanism and rapidly can lead to death of the horse.

     To prevent hyperthermia in the horse, some common-sense horse management guidelines should be followed. The horse should have access to some type of shade. During extremely hot weather, simply being able to get out of the sun allows the horse to stay cooler. The horse should be properly conditioned for work in hot, humid weather. If the horse is exercised regularly throughout the year and is physically fit, it can deal with temperature extremes more easily.

     When the weather turns hot and humid, shorten work periods and give the horse frequent walk breaks. These breaks give the horse’s body cooling mechanism a chance to “catch up” and give the rider time to carefully observe the horse for any signs of distress. If possible, take advantage of cooler temperatures by riding early or late in the day.

     Unless the horse is hot from exercise or extremely thirsty, it should always have free choice access to fresh, clean water. During hot weather, a horse easily can consume over 25 gallons of water daily. Although drinking water does not appreciably lower a horse’s body temperature, adequate water intake is essential for proper functioning of the body’s cooling mechanism. For example, a horse can loose approximately 3 gallons of sweat during one hour of hard work in hot weather. Along with the water lost in sweat, large quantities of sodium, potassium and chloride leave the body. Balanced horse feeds contain proper amounts of these minerals (electrolytes) to supply the needs of a normal horse. However, if a horse is consistently working in hot weather or is obtaining all its ration from pasture, a free-choice trace mineral salt block will help the horse replace electrolytes lost in sweat.

     If the horse does develop hyperthermia, first aid is essential to save the horse’s life. Immediately take steps to lower the horse’s body temperature. Spray the horse with cool water*. Get the horse out of the sun, and keep it moving slowly to increase air circulation over its body. If a fan is available, put the horse in front of the fan. Have someone else phone your veterinarian immediately. In true cases of hyperthermia, you need to lower the horse’s body temperature first, and the time it takes you to stop and phone the veterinarian could be fatal to your horse. Once you have contacted your veterinarian, follow his advice to help your horse recover completely.