Competing in the heat--USHJA article

Some Advice From the USHJA Horse Welfare Committee onCompeting in the HeatMaintaining optimum performance while protecting your horse from the effects of extreme heat.
By Dr. Mark Baus

With the summer months approaching, it is useful to review some basic methods of dealing with the heat while competing at horse shows. The horse evolved over time to cope with the vast extremes of temperature that exist on the great plains of the world. If the horse is simply provided adequate nutrition, dealing with cold temperatures is not a problem. Dealing with summer heat, while performing as an athlete, is another story.

Horses generate huge amounts of heat from their muscles while undergoing physical exertion. Most of this heat is dissipated from the skin in the form of evaporative cooling [sweating] along with increasing circulation through the skin to provide further cooling. Although horses are well adapted for most activities during severe heat, it is important to consider several things to prevent and treat overheating and heat stroke.

The first consideration is determining activity levels based on temperature and humidity levels. By adding temperature and humidity, the heat index can be calculated and standards for activity can be set.

Most levels of activity for a heat index under 130 [e.g. 70 F & 50% humidity] are not a significant challenge to the horse’s ability to regulate body temperature. As the heat index approaches 150, especially as humidity exceeds 75%, the horse’s cooling mechanism becomes significantly limited and activity levels need to be monitored closely. As the heat index exceeds 180 [e.g. 95 F & 90% humidity] all activity should be significantly limited or even postponed.

Although electrolyte administration is widely used in the horse world, the need for them is minimal if a high quality hay and premium grain formulations are fed consistently. Most electrolyte supplements are high in sugars to enhance palatability and to allow them to be added to the drinking water. I am reluctant to add electrolytes to the water since it may inhibit water drinking and it is also difficult to determine the exact amount they ultimately receive. Electrolytes are best used at manufacture’s recommendations and only during periods of added heat and activity.

At horse shows, it is important to provide your horse with shade, especially during periods of inactivity. Since most horse’s skin is heavily pigmented, the sun’s rays contribute significantly to heat build-up during hot weather. It is also important that horses have access to drinking water. If your horse has been significantly exerted it is okay to allow water drinking to avoid the complications of dehydration. In addition to drinking water, water for bathing and cooling should also be provided for added cooling when necessary. When at rest, each horse should have access to 2 buckets of clean water at all times. If electrolytes are added to the water, make sure it is added to only one of the two water buckets to give the horse a choice of drinking from either bucket.
Although it is important that our horse’s performance be kept at optimum levels for competition purposes, protecting their health and wellbeing during hot weather is always the principle concern. Recognizing early signs of heat exhaustion and heat stroke is critical. Most riders and trainers are adept at monitoring their horse’s response to exertion by watching respiration and overall vitality. As heat levels are rising during periods of activity, the horse’s cooling mechanism is challenged and they will attempt to dissipate heat with increased respiration. This may be the first sign that the horse is no longer compensating for overheating.
Signs of impending heat stroke are critical to recognize:• Body temperature in excess of 104 F.• Rapid breathing and elevated pulse.• Weakness and depression.• Refusal to walk or eat.• Dry skin.• Total collapse.

If your horse is showing signs of heat stroke, it is important to take the body temperature as soon as possible. The normal body temperature ranges from 99.0 F. to 100.4 F. As the body temperature exceeds 102 F, it will become necessary to provide additional cooling quickly. Cold hosing or ice packing at sites of major blood vessels will be helpful. This would include the jugular veins along with the blood vessels on the insides of each limb. If heat stroke is suspected, drenching the body with water will provide immediate cooling to lower the body temperature effectively.

It is important to call your veterinarian at the first sign of heat stroke. As heat stroke develops, blood flow is shunted away from the intestines and vital organs so the potential for catastrophic effects increases dramatically if the body temperature is not brought down to normal quickly.
Since sweating is the horse’s primary method of shedding excess heat, it is important that your horse’s ability to sweat is constantly monitored. Anhydrosis, a disease in horses that limits sweating, is seen fairly commonly in the southern states but it can affect any horse during hot weather. Veterinarians have tried many therapies to treat this disease but the key to dealing with anhydrosis is early recognition. Many of these horses are simply not able to compete during hot weather conditions.

If your horse is in a good health and good physical condition, it is unlikely you will encounter a significant problem with hot weather. The key factor avoiding heat related complications is simply using common sense to determine the proper level of activity for your horse. In my experience at all levels of horse shows, riders are more likely than horses to succumb to the effects of competing in hot weather. If conditions are too rigorous for the competitors, it is likely too much for our horses as well.