Hot, humid weather can result in heat stress if horses are exerting themselves in work or don’t have shade in a pasture. Monitor horses closely in extreme weather conditions, whether they are being ridden, turned out, or even in the barn.
It is important to cool a horse quickly if he is overheating. Some of the tactics for cooling a hot horse after exercise also work for horses on the verge of heat stroke even without exercise.
Air movement is very effective for cooling horses and often more comfortable for the horse than hosing him down or splashing him with ice and water. If he is dangerously overheated, however, most veterinarians recommend applying cold water, said Mike Foss, DVM, of Alpine Veterinary Hospital, in Hood River, Oregon, who has managed many horses overheating on endurance rides.
When a horse’s temperature reaches 104 or 105 degrees Fahrenheit, the situation becomes dangerous. The fastest way to cool him is to apply cool water over the body, especially on areas where blood is near the skin surface (neck, chest, belly, legs). The veins under the skin on a hot horse will stand out prominently, bringing overheated blood to the surface for cooling via sweat evaporation.
“You can’t just put cold water onto the horse; you also have to scrape it back off because it heats up immediately, creating a layer of insulation that slows the cooling process,” said Foss. “It works best to put cold water on, scrape it off, and put on more. You can readily feel it warm up, so you scrape it off, taking the heat with it.”
“People always used to be very cautious about using cold water over the rump, but we know now that putting cold water on the large muscles doesn’t cause muscle problems
, and may be necessary in an emergency,” he added.
You can add rubbing alcohol to cold water (about a pint per gallon of water) to enhance evaporation. If you think the horse is severely overheated, take his temperature so you can track whether you are lowering his temperature. Take his temperature every 10 minutes, and stop cooling the horse when his temperature gets to about 103 degrees, because you don’t want to chill him, said Foss.
Some people walk the horse slowly in a circle between water applications to help provide more air flow around the body and allow any breeze to hit both sides of the horse. This gentle exercise also helps the circulation continue to bring overheated blood to the skin surface for cooling.
“Use common sense,” said Foss. “If the horse is overheated at the end of his workout, try to get him in the shade, take off all tack (to enable air flow around the whole body surface), and use lots of water. If your water supply is limited, use a sponge to put it on and wipe it off, so you aren’t using a lot of water. If the horse is overheated, he should not return to work that day even if he’s cooled out.” If a horse was severely overheated, he might need several days to recover.
Work with your veterinarian if your horse is overheated. “Heat stress can trigger other problems, including laminitis,” said Foss. “We don’t always know how hot the horse actually got (before we checked his temperature) or how stressed he was or how much damage might have been done.”