Equine Heat Stress: 4 Tips to Beat the Summer Heat

Heat and humidity are added risk factors for equine heat stress in horses during training, competition, and transportation. Especially during the busy summer travel and show season, it’s important to make sure your horse is not becoming overheated, stays sufficiently hydrated, and remains comfortable, even when temperatures soar.

“Horses are better equipped to work in cold weather than in the heat,” said Katie Young, PhD, equine nutritionist and manager equine technical services for Purina Animal Nutrition. “They build up a tremendous amount of body heat as a result of fiber digestion and muscle exertion, plus insulation from their haircoats and body fat, and hot, humid weather can make heat dissipation extremely difficult.”

Young and Karen Davison, PhD, equine nutritionist and sales support manager, shared the following tips for horse owners to help ensure a healthy summer season and reduce equine heat stress.

1. Head off heat stress. A horse’s main cooling mechanism is evaporation of sweat from the skin surface. Increased humidity reduces this evaporation, decreasing the horse’s ability to cool down. Under extreme heat, especially with high humidity, the body’s cooling mechanisms might not work well enough to dissipate the heat generated. This can lead to heat stress, which is hard on the body and can impair performance.

A simple calculation can help you determine your horse’s risk level for heat stress. Take the ambient temperature (measured in degrees Fahrenheit), add the relative humidity (%), and subtract the wind speed (miles per hour, or mph). So, if the ambient temperature is 98° F with a 55% relative humidity and wind speed of 5 mph (98 + 55 – 5), you’re left with the number 148. This value represents your horse’s risk of heat stress:

  • 130 or less: The horse’s own cooling mechanisms should work effectively.
  • 140 to 170: The horse has partial cooling capacity and might need some assistance cooling down.
  • Higher than 180: The horse is at high risk for heat stress or stroke.

2. Don’t hesitate to hydrate. Sweat generated during work robs the body of large amounts of fluids and important nutrients that must be replenished. So it’s very important to provide adequate clean water to help horses stay hydrated. In some situations, such as travel, it can be hard to persuade your horse to drink enough water. Compressed hay blocks soaked in water can be very helpful in these situations, as a horse will sometimes eat a hay block with water even when he turns up his nose at a bucket of water.

3. Amp up electrolytes. Electrolytes are electrically charged mineral salts that play a major role in water balance and are integral to nerve and muscle function. An electrolyte imbalance can lead to heart problems, digestive dysfunction, muscle cramps, and nervousness. The primary electrolytes lost in a horse’s sweat are sodium, potassium, and chloride.

Horses working at light to moderate levels will generally receive adequate electrolytes from a nutritionally balanced feed, good quality hay, and a salt block or a couple of ounces of loose salt each day. Even if these horses are sweating a bit, a good diet (including free choice or top-dressed salt) along with plenty of clean water is usually adequate to replenish the electrolytes lost in sweat. However, if your horse works very hard in hot, humid climates, and sweats a great deal, he will likely need additional electrolyte supplementation.

4. Evaluate the environment. Pay attention to environmental conditions and try to avoid working your horse when the risk of heat stress is high. Be sure to provide adequate water for hydration and electrolytes to replenish sweat loss. Try to work in the shade, turn on some fans, and use cold water to wash down your hot horse.

Summer is great time to enjoy and bond with your horse! Just remember to help him beat the heat through these late summer months by giving him the care and attention he deserves.

Source: The Horse and Purina Animal Nutrition

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