Managing Heat Stress in Horses

— Written By Zack Taylor and last updated by
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Independence Day is just around the corner, and while we are now headed into the “dog days of summer,” summer heat has been with us now for some time. Extreme heat arrived early this year, we typically see our hottest temperatures of the year in July and August, but don’t expect it to go away early as well. As the heat settles in, we need to think about how our animals are handling the heat. Horses often need to be worked or ridden, but as the heat cranks up, we must make some adjustments to our schedules.

Fortunately, horses are effective at cooling themselves through sweat, and can acclimate to high temperatures. However, monitoring and adjusting working and riding schedules is still necessary on hot days. As you likely are aware, high humidity is very common here in North Carolina. As the humidity increases, the ability of the horse to cool itself through sweating is decreased since evaporation decreases during humid conditions. One good way to determine the cooling ability of a horse is to use the sum of air temperature and relative humidity. We have a guide we can go by when using this sum. If the sum is less than 130, horses are effective at cooling themselves. A sum of 130 to 150 means that their cooling efficiency will be decreased, and work should be lighter with frequent breaks. A sum over 150 and working or riding a horse should be avoided. This is common in North Carolina during the summer, for example, a 90-degree day with 60 percent humidity would meet these criteria. Sums occasionally climb over 180, in which heat could be fatal to a horse if it is stressed. If a horse must be ridden on hot days, here a few tips to help avoid heat stress:

  • Adjust you schedule. Ride early in the morning or late in the evening.
  • Keep work light and allow frequent breaks.
  • Watch for normal sweating
  • Use fans to create airflow and work horses in the shade when possible
  • Provide access to cool clean water at all times, and offer frequent water breaks to your horse.

If overheating occurs there can be serious consequences. An overheated horse will have a rectal temperature above 103 degrees. If your horse is over heated, use a sponge or spray of water to help cool the horse, being sure to immediately scrape off excess water, repeating until the horse has cooled. Excess water should be scrapped away since water may serve as insulation, actually increasing body temperature. If rectal temperatures reach 105 degrees, ice can be added to the water to increase cooling. A rectal temperature above 106 degrees is indicates that heat stroke is likely. Other signs of heat stroke include notable distress, muscle weakness, incoordination, extreme signs of dehydration such as dry mucous or a skin tent lasting 4-10 seconds, and collapse. Heat stoke is a serious condition that will require emergency veterinary attention, including intravenous fluids with electrolytes.

To reduce heat stress in the summer, consider some of the following tips:

  • Provide turnout during cooler times of the day, such as night, early morning, and late evening.
  • Provide access to shade. Remember shade from some structures may block airflow and reduce evaporative cooling.
  • Fans will help improve airflow, be sure plugs and cords are out of horse’s reach. Misting fans can enhance cooling ability.
  • Ensure access to clean and cool water at all times. Water sources may need to be cleaned more often during hot weather as bacteria and algae growth is more common during hot weather.
  • Consider adding electrolytes when heavy sweating is observed. Offer access to clean water as well as some horses may refuse or drink less water containing electrolytes due to the taste.
  • Clip horses with long coats to enhance cooling.
  • Transport horses during the coolest part of the day. Never park loaded trailers in in direct sun, and ensure trailer are well ventilated and horses have access to water.

If you have questions about heat stress or cooling an overheated animal, give me a call at 919-775-5624. If your animal is exhibiting signs of heat stroke, contact your veterinarian immediately.

Zack Taylor is the Agriculture Agent – Field Crops and Livestock, and Pesticide Coordinator for North Carolina Cooperative Extension in Lee County.