by Kristin Pitzer
With temps soaring into the 90s and above, humidity levels ramping up and insect activity increasing, there’s no doubt about it: the “dog days of summer” are here. The phrase refers to the 20 days before and after the star Sirius, or the “Dog Star,” rises and falls in conjunction with the sun and is typically used to describe the hottest and most humid days of summer.
Despite the often-unpleasant weather, many shows and events take place during this time. But as the temperature rises, the risk of heat stress in horses also increases, especially if they’re working vigorously. Quarter Horse News spoke with Jamie Pribyl, DVM, Professional Services Veterinarian at Boehringer Ingelheim, to learn how to ride and show safely during the hot days ahead.
Temperature and Humidity Play the Biggest Role
While there are several factors that can cause a horse to go into heat stress, temperature and humidity levels are the biggest. Once the temperature rises above 80 degrees, even without humidity, horses struggle to stay cool, especially if they’re in heavy work.
“And if our humidity is elevated, that’s going to add to it,” Pribyl said. “You can add the ambient temperature, so let’s say it’s 90 degrees, to the percent humidity, and if you get a number over 150, then we’re at a really high risk. At that point, the horse has a really difficult time cooling itself with its regular mechanisms.”
Other factors that contribute include being turned out in the sun with no shade; being shut into a poorly ventilated barn; standing in a trailer that is parked in the sun; and not having access to water.
Horses Need Help Acclimating
Horses that live in cooler parts of the country but travel to hotter locations for events may find themselves struggling with the heat even more than their peers. It takes a couple weeks for a horse to acclimate to a new environment, Pribyl noted. If you don’t have extra time for your horse to adjust, there are a few things you can do to help protect him.
“If you’re traveling during the summer to a hotter area, try to do your travel overnight because it’s cooler then,” Pribyl said. “Make frequent stops to give them some water, and if you’re providing them with electrolytes, make sure they also have plain water so that if they don’t like the electrolytes, they’ll drink the plain water instead.”
During the event, try to ride during the coolest parts of the day — mornings or evenings — and limit warmups to retain energy for the show pen. After your run, walk your horse out until their breathing has returned to a normal level, and offer them small amounts of water — half to one gallon every 15 to 20 minutes as you’re walking them out. You can also cold hose them continuously to help them cool, but if you stop while they’re still hot, make sure and scrape any insulating layers of water off to dissipate the heat.
Watch for These Signs
Horses that are suffering from heat stress may not exhibit obvious signs immediately. In fact, they might not look that different at first from a horse that has just been ridden or worked hard.
“If the horse is working, we’re used to seeing them sweat, but a horse in heat stress is going to be sweating excessively,” Pribyl said. ‘That respiratory rate’s going to kick up, and it’s not going to come down as quickly as we would expect it to if they’re being rested. Their heart rate is going to kick up as well. We might see lethargy or fatigue, and then sometimes we can see decreased appetite as well.”
If you don’t catch the early symptoms, a horse that is progressing into heat exhaustion may stop sweating entirely, a condition called anhidrosis. They will become severely dehydrated and may develop muscle tremors and weakness. If their symptoms continue to progress, their condition can become an emergency very quickly.
“The severe symptoms include a very high body temperature —if you were to take the rectal temperature, it could be over 103 or over 105. Basically, the cooling mechanisms have completely failed,” Pribyl said. “At that point, we’re going to see labored breathing. We could even see collapse or some neurologic symptoms like confusion and disorientation. They might develop colic symptoms, and we can start to see organ failure.”
Beware of Anhidrosis
Anhidrosis affects anywhere from 2% to 6% of horses, particularly those living in hot, humid climates. If you notice your horse has stopped sweating, stop all activity immediately. Get them to a cool, shaded area, take their temperature and start working to cool them down. Monitor them for signs of lethargy, reduced appetite and dehydration.
“If they have a temperature above 102 and they haven’t just been vigorously exercising, that’s a tip that this horse isn’t cooling itself,” Pribyl said. “Hose them with cold water, focusing on areas of the horse where the large blood vessels are located, so the neck and the legs. The whole body is great, but focus on those areas. Offer them water, give them electrolytes and monitor those vital signs.”
If your horse is suddenly experiencing anhidrosis when he never has before, call your veterinarian immediately.
Healthy Horses Handle Heat Better
If humans could control the weather, we’d likely never have to worry about heat stress again. But, since we can’t, the best thing you can do to protect your horse from overheating is to feed him properly, offer him plenty of water and shade, and keep him in shape for the type of riding and showing you enjoy.
One tool in your toolbox that is helpful in preventing heat stress is having your horse examined regularly by your veterinarian. He or she can help assess your horse’s body condition and alert you if your horse has a condition that makes him more susceptible to heat illnesses.
“If they’re overweight, that layer certainly insulates them, and that’s going to make it harder for them to cool,” Pribyl said. “Any horse that has PPID — so horses with Cushing’s disease — if they have excess long hair, they’re going to be more susceptible, especially in the summer months. What can we do? Have the overweight horse lose weight, and with the PPID horse, we could body clip them.
“It’s important to monitor all horses during extremely hot conditions, even if you aren’t competing,” Pribyl added. “If you ever suspect a problem, it’s best to call your veterinarian, as he or she knows your horse and can help determine appropriate next steps.”
This article originally appeared on Quarter Horse News and is published here with permission.
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