How to Prevent Heat Stress in Your Horse

Kathleen P. Anderson, Phd, answers this reader question.

Credit: Arnd Bronkhorst – When you work your horse, his temperature can be between 101 and 103 degrees. Anything that is above 103.5 degrees is an indication of heat stress.

Q: Now that the hot weather is moving in, I’m worried about my horse becoming overheated during our training sessions. I try my best to ride early or late when it’s cooler, but some days that’s not an option. What steps can I take to prevent my horse from becoming too hot?
Name withheld by request

Kathleen P. Anderson, Phd: Summer heat can make it challenging to keep your horse fit. If you follow a few essential rules, you can enjoy dressage training in hot weather without risking health problems. If the heat is extreme, especially if you live in an area with heavy humidity, your main concern should be to avoid heat stress or heat exhaustion in your horse. Signs of heat stress include sweating profusely, high or fast respiration and panting like a dog instead of taking deep breaths. You can also check for signs of dehydration by looking at the horse’s mucous membranes by holding up the upper lip and pressing on his gums. If the area you pressed doesn’t return to pink quickly, that can be a sign of dehydration. Also, you can perform a pinch test by briefly pinching your horse’s skin. If the pinched area doesn’t quickly smooth out, it can be an indicator of dehydration. You can also take the horse’s rectal temperature—100 degrees Fahrenheit is a normal temperature. When you work your horse, his temperature can be between 101 and 103 degrees. Anything above 103.5 degrees is an indication of heat stress. 

When your horse has been sweating excessively after high levels of work, you need to think about water and electrolyte loss and replenish both after work. If you have a competition coming up, consider preloading your horse with electrolytes either just before the show or a couple of days ahead of time. If you live in a southern region, it can be helpful to train in the morning, late afternoon or evening. Avoid riding in the middle of the day when it’s hottest. Since indoor arenas can get excessively hot in the summer, storing the heat, consider riding in a shady spot outside. 

An overweight horse is more prone to heat stress. A horse whose body condition score is in the 8 to 9 range doesn’t handle heat as well as a horse whose body condition is 5, 6 or 7. Potentially, it might be necessary to change his diet before or during the summer. 

Make sure your horse has unlimited access to salt. While most commercial feeds have salt in them, it might not be enough when the horse sweats a lot in the summer, losing salt through the sweat. Don’t worry about your horse getting too much salt when providing salt blocks or loose salt. Horses take only as much as their system tells them they need and are replenished. 

Monitor the amount of water your horse drinks after a workout. Right after work, you don’t want him to drink a whole lot of cold water. Rather, give him small amounts of water at a time, until he doesn’t want any more. Ambient water temperature is best. Overdoing cold-water intake in a hot horse can cause colic or laminitis. 

If your horse is excessively hot, be careful with hosing him down. Too much cold too quickly can put the horse in shock. First, just hose off the legs, letting his body acclimate. After a while, you can hose off the rest of the body. 

A few horses suffer from a condition called anhydrosis. Such horses don’t sweat well (they still can be sweating, just not enough), which causes them to overheat easily. Sometimes such horses might have a metabolic or mineral imbalance, but generally anhydrosis cannot be remedied. When you ride such a horse, be careful how you manage him. When he starts to pant, immediately back off the level of work so he can cool off.

Kathleen P. Anderson, PhD, has been the extension horse specialist at the University of Nebraska since 1991. She oversees the adult extension horse program and teaches undergraduate courses in the animal science department. She was the recipient of the 2014 American Society of Animal Science Equine Science Award.






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