Beating the heat: When is it too hot to ride your horse?

A horse can lose up to four gallons of perspiration an hour when exercised in hot, humid conditions.
A horse can lose up to four gallons of perspiration an hour when exercised in hot, humid conditions.

Heat and humidity is a “hot topic” for horse riders as temperatures increase, and several experts have weighed in on how equestrians can keep their animals — and themselves — safe.

Discussions by a panel of horse-care experts at the recent Kentucky Equine Networking Meeting (KENA) spoke of how riders can help their horses cope with the oppressive heat and humidity.

Dr Bob Coleman, an equine extension specialist with the University of Kentucky, spoke of temperature and its effect on horses, both while they are in the field and when they’re asked for physical exertion. He explained that temperature alone is not the only variable that can affect a horse’s ability to sweat to keep itself cool: humidity, wind speed and the amount of sunshine also affects heat dissipation in horses.

The temperature and the relative humidity as a percentage can be combined to calculate the comfort index for horses, Coleman explained. This number — the temperature in F° plus relative humidity — will assist in determining if it’s too hot to exercise a horse. If the sum is below 130, thermoregulation should not be a concern. When the comfort index is between 130 and 150, horses will sweat, but they can exercise without major problems. When the comfort index exceeds 150 and the humidity is greater than 75 percent, heat dissipation may be an issue and riders should monitor their horses carefully. If the comfort index exceeds 180, a horse should not be exercised, as it will be unable to dissipate enough heat to stay safe.

Nicole Bianco, a registered dietitian and graduate assistant with UK athletics, addressed potential human-specific issues when working or riding in the heat. Dehydration is a serious concern for anyone exerting themselves in heat and humidity, she said. Dehydration can present as dizziness, fatigue or nausea, and can lead to decreased stamina and make people more prone to injury. She suggested that people who will be working or exercising in the heat hydrate first with water, but they can also drink milk, juice, sports drinks or tea. Eating fruits and veggies that contain a lot of water will also help replace fluid lost to sweat. Paying attention to how one feels and acting accordingly is imperative for human safety when temperatures soar, Bianco said; this could include stopping work, getting out of the sun or entering an area with air conditioning.

Dr Bruce Howard, the Interim Equine Medical Director for the Kentucky Horse Racing Commission, noted that his main role was to keep both horses and humans safe; the decision to cancel racing is not one that is taken lightly, and he confers with stewards and track management when heat indices rise.

Ellis Park racetrack in Henderson, Kentucky, sits in a bowl of land, where the heat sits on the track, Howard says. When it’s 92 or 93 degrees outside and most other tracks are still running, Howard considers the weather conditions carefully: “If it’s 92 or 93 out and there’s no wind or clouds, it will be too hot to race at Ellis,” he said.

The “magical” heat index number for mandatory racing cancellation is 108 Howard says; at 105 track management gets worried.

But horses do fine racing on hot tracks when they’re given the opportunity to adapt, he notes. It’s the horses who are not from the area that arrive to race that cause him concern. Horses in heat distress will hold their ears to the side, have a dull eye, violently swish their tail and kick with their hind legs. A horse in heat distress won’t drink, but the condition is rarely fatal when addressed as soon as possible, Howard says.

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