As Summer Begins, Equine Heat Stress Looms

Heat loss for all horses becomes difficult when temperatures exceed 90°F, so avoid exercising them during very hot periods.

Photo: Thinkstock

With summer upon us, it’s a good time to start thinking about protecting horses from inevitable heat stress conditions.

“The combination of hot, muggy weather conditions prompts some real concern for humans, as well as livestock and pets,” said Tom Priddy, meteorologist for the University of Kentucky College of Agriculture, Food, and Environment. “The livestock heat stress index is a combination of air temperature and humidity. That one-two punch makes it hazardous for people and animals. Dew point temperatures above 65°F lead officials to declare conditions dangerous for livestock.”

The Livestock Heat Stress Index helps producers know when heat stress could create a problem for their animals. Periods of heat stress call for livestock producers to be vigilant in making sure their animals are able to withstand the conditions.

Heat loss for all horses becomes difficult when temperatures exceed 90°F, so avoid exercising them during very hot periods. When humidity is high, even temperatures much lower than 90°F can pose problems. Horse owners can reduce heat stress by scheduling activities during the cooler part of the day and giving horses plenty of water. Transporting horses during the cooler hours of the morning or evening can help. To reduce the risk of dehydration and heat stress when traveling in hot weather, give horses access to water before, during, and after transportation.

Offer horses frequent drinks of water during work in hot weather. Allowing them to drink during work helps maintain water balance and relieves the urge to drink a lot of water after exercise. After a hard workout, water horses out gradually.

Even nonworking horses will double their water intake during hot weather, so be sure plenty of water is available to horses in pastures, paddocks, and stalls.

Lactating mares will have especially high water requirements because they are using water for milk production and heat loss.

Hot weather also will increase horses' need for salt, which is lost during sweating. Heavy rains can "melt" salt blocks in pastures, so check salt licks periodically.

Visit the UK Ag Weather Center website at to keep up with current weather, forecasts, heat stress indices, and more.

Aimee Nielson is an agriculture communication specialist at the University of Kentucky.

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