How Heat Stress Occurs
Heat stress occurs when equine athletes' body temperature exceeds 104 degrees Fahrenheit, according to University of Illinois professor Kevin H. Kline PH.D. Normal temperature is around 101 degrees, and temperatures of 107 or 108 degrees are considered a trigger for heat stroke.
Equine heat stress is typically caused by a horse being worked hard in hot temperatures. It is most likely to occur during the warmest months of the year and the hottest times of the day. A horse that is suffering from heat stress is creating more heat than its body can naturally dissipate through sweating. Even well-conditioned equine athletes may overheat in extremely hot temperatures, so it is important to understand both the contributing factors of heat stress and the treatments in order to prevent your horse from being seriously harmed by overheating.
Factors that Contribute to Heat Stress
Factors that play a part in contributing to equine heat stress include temperature, air flow, dehydration and physical fitness. Individual temperament can also play a part, as some horses have a tendency to get worked up and stressed more quickly than others, which can lead to additional heat.
Heat stress typically occurs when several contributing factors come together at one time. For example, an overweight or out of shape horse that is taken on a two hour trail ride in the middle of a hot summer day with little to no shade is more likely to suffer from heat stress than a fit horse on the same trail ride or horses that went on a trail ride on a cool, well-shaded trail.
Heat Stress Symptoms
Symptoms of heat stress include excessive sweating, reduced skin elasticity, slow capillary refill time, lack of sweating caused by a condition referred to as anhidrosis, which occurs when a horse is unable to sweat, and colic.
Horse owners can test a horse's skin elasticity by pinching a small fold of its neck skin between their fingers and then releasing it. If it goes back instantly, the horse is properly hydrated. If the skin takes more than a second to completely go back in place, there is a good chance the horse is dehydrated. Taking the horse's rectal temperature is also a good indicator of heat stress. If the temperature is 104 F or above, you should assume the horse is suffering from heat stress and begin treating it immediately.
Preventing Heat Stress
Preventing heat stress is all about intelligent horse management. Always make sure horses have plenty of water available at all times. If the weather is unusually hot, add electrolytes to the water to provide extra minerals and hydration. Make sure the barn and pastures offer plenty of airflow, either naturally or with the aid of fans, and plenty of shade.
Schedule riding times to avoid mounted activities during the hottest parts of the day. Whenever possible, ride in covered areas or shaded trails. Avoid working horses hard during unusually hot temperatures or if the horse is out of shape. Make sure to make time for both a proper warm up and cool down period before and after riding.
Treating Heat Stress
In the event that a horse is showing symptoms of heat stress or stroke, the veterinarian should be called immediately. In addition to calling the vet, the horse's owner or rider should stop riding, move the horse into a cool or shaded area with good airflow, offer the horse water, and hose the horse down with cool water under the veterinarian arrives.