By Heather Heiderich-Farmer, DVM

We all long for warmer weather and the longer rides summer affords. But heat and humidity are major concerns for rider and horse since heat-related illness can be dangerous – even fatal. Horses have efficient natural thermoregulatory systems to cool themselves, but sometimes they are overwhelmed and cannot compensate for the heat. Hyperthermia or heatstroke results when your horse is unable to control his internal temperature and it starts to rise. 

Signs of heatstroke are elevated respiratory rate – 40 to 50 breaths per minute (normal: eight to 16) – that does not slow when at rest; a heart rate over 80 beats per minute (normal: 36 to 44 beats per minute) that does not slow down after a few minutes of rest; elevated rectal temperature over 103˚F (normal: 99 to 100.5˚F); lethargy; and/or profuse sweating or absence of sweating altogether. If left untreated, hyperthermia can cause death. It is neither the heat alone nor the humidity alone that is concerning, but the two factored together. Most researchers define high heat as over 86˚F and high humidity as 80 to 85 percent. 

Hyperthermia can occur when one of these three things are present: inadequate (fitness) conditioning, extreme hot and humid conditions, or a weakened thermoregulatory system. 

If you want to ride, but you are concerned that it is too hot or humid for your horse, there are plenty of ways to keep your horse cool while riding. 

Consider the time of day you ride. The hottest time of the day is the afternoon. Try getting up an hour early to ride. Or, if you are not an early riser, try riding in the late evening. These times when the sun is not as high in the sky are cooler times to ride.

Ride in the shade. If you have a covered or indoor arena with plenty of air circulation, ride there. If you do not have a covered space, try riding on trails or in and around the edges of fields that have tall trees for shade. This will lesson your horse’s exposure to the direct heat of the sun. 

Condition properly. Evaluate your horse’s physical condition and his/her body condition score. Most obese or poorly muscled thin horses cannot combat the extra stress of working in the heat. If your horse has not been in regular work or you are unsure about a new mount’s work history, begin your summer workouts slowly with approximately five to 10 minutes of trot only. Increasing your total workout time by five minutes each week, as well as increasing the intensity or speed at which you ride, will give your horse time to acclimate to the heat and humidity. 

Replace electrolytes. Give your horse electrolytes in a water bucket or in feed. The horse loses salt and other minerals when he sweats, and these must be replaced. When adding electrolytes to water, make sure you also have a water bucket available without electrolytes. The horse might not like the taste of the electrolytes or he might not need many electrolytes. 

Cool the horse properly. After you ride in the heat apply cool water to your entire horse. Spend time hosing his largest muscle areas and the largest and closest-to-the-surface blood vessels, the jugular vein in the neck and the saphenous vein on the inner thigh. Doing this cools the body faster. 

Install a fan if your horse sweats while standing in the stall; some of these fans include water-misting systems. 

If the horse develops hyperthermia:

• Stop activity immediately and remove the saddle;
• Hose your horse with the coldest water available or a water/alcohol mix. Scrape the used water off and repeat;
• Offer your horse water and allow him to drink;
• Move him to the shade or a breezy location; and
• Call your veterinarian.

The earlier you recognize the signs of hyperthermia, the earlier the veterinarian can begin treatment and prevent further damage. Acclimating to heat and humidity does not guarantee that your horse will not get hyperthermia, so always keep an eye on your horse’s health when riding this summer. Have a great time on horseback! 

AAEP Forum article courtesy of The Horse magazine, an AAEP Media Partner.