Beat the Heat

Photo: Anne M. Eberhardt

As tough as steamy summers can be on humans, they can be even tougher on horses. That's because instead of choosing how they'll deal with the heat, horses often have to depend on us to make the right management choices for them.

For advice on making those choices, we've turned to two equine veterinarians practicing in Florida, where heat plus humidity can deliver a double whammy to horses. At the University of Florida, in Gainesville, Amanda House, DVM, Dipl. ACVIM, is an assistant professor in the veterinary school and a state extension specialist. And Heather Farmer, DVM, owner of Equine Performance Veterinary Practice, in Lake County, Fla., tends to equine competitors that must work and perform throughout the summer.

Turnout Tips

According to House, horses can live outdoors during summer months 24/7 if, in addition to adequate forages, they are provided with two must-have ingredients: fresh water and shade.

Water, in particular, must be plentiful and readily available. Position troughs in pastures so one horse can't block others from the water source; if using water buckets, provide one more bucket than you have horses turned out. Check water levels periodically, as even automatic waterers can clog. Clean buckets daily, and dump, clean, and refill troughs every two to three days, since stagnant water provides an ideal breeding ground for mosquitoes. Provide free-choice access to vitamin/mineral salt blocks in pastures if they're not available in each horse's stall.

As for shade, "being able to escape from the direct heat of the sun is really critical," says House, adding that "in this part of Florida we have large oak trees that provide excellent shade." Besides trees, she says, a shelter such as a run-in shed can help horses escape the elements.

In Farmer's experience most horses prefer to seek solace from sun under trees, where there's usually a little breeze, rather than in a windowless lean-to or run-in shed. And "as long as there isn't lightning or a real downpour, most are happy enough staying out in the rain," she says.

For times when horses aren't standing in the shade, Farmer says mesh fly sheets with ultraviolet (UV) protection work well to help shield a horse from the sun's rays as well as biting insects, without making making their wearers any hotter. She also recommends fly masks, "because flies are so annoying in the summertime that horses' eyes tear constantly; and because without masks, horses that like to roll and 'itch' in the sand can end up with corneal ulcers."

Masks also block light well enough to help prevent sunburn on sun-sensitive, nonpigmented areas such as those seen around some Paint horses' eyes, says Farmer, and "long-nose" masks provide at least some protection to easily burned noses.

Especially where shade is limited or absent, Farmer suggests limiting turnout to four hours or less each day. "(Turn out from) early morning until noonish, then again for a couple of hours after 5:00," she advises. Once or twice during turnout on particularly hot days in these shadeless pastures, check horses for dehydration: Does a fold of pinched skin snap back quickly or slowly when released (the latter indicating dehydration)? Are gums a healthy pink color and wet to the touch, or are they pale and tacky? Also observe respiration (a normal respiratory rate for an adult horse is eight to 12 breaths per minute), because "a horse that isn't dissipating heat adequately by sweating will breathe faster, trying to cool down by exhaling," Farmer says. If your horse shows any of these signs of dehydration, bring him in from the sun, hose him, and sweat-scrape off most of the moisture; when his breathing slows, he can be turned out again.

Barns: Go with the Flow

For heat relief in the barn, says Farmer, "the biggest thing is to keep air moving." Your prime ally? The fact that heat rises. Louvered roof vents or cupola vents let out hot air, and an exhaust fan can amplify the effect. Open doors and windows allow intake of fresh outside air, which warms, rises, and draws in yet more air. Installing window- or table-type fans--mounting them securely so fans and cords can't be reached by curious muzzles--promotes air circulation and, thus, equine comfort.

Airflow also plays an important role in insect control. "Flies aren't very good at flying in wind," Farmer says, "so fans in or above the stalls help," creating a current in which flies cannot fly (or alight on horses) well.

In stalls, just as in paddocks and pastures, horses need constant access to clean, fresh water. Some horses habitually dunk hay or dribble grain into their water, which can gunk up the bottom of a bucket or block a waterer's fill hole; combat this by dumping and cleaning buckets and checking waterers regularly. On waterers with a pedal horses must press with their noses for fresh water, make sure debris isn't jammed under the pedal. Checking these water sources also allows you to monitor your horse's water intake and discover if he's not drinking enough sooner than later (a 1,100-lb horse at rest should typically drink 4-9 gallons per day).

Workouts and Cool-Downs

University of Guelph researchers determined in a recent study that horses succumb to heat stress three to 10 times faster during workouts than their two-legged counterparts. Horses are large and possess higher percentages of active muscle than humans do during exercise--muscle that produces a lot of heat during use. Also, less sweat evaporates from equine athletes' bodies as compared to human athletes simply because the horse produces much more sweat than can be evaporated.

To avoid heat stress, House says horse owners should "focus on exercising and training in the coolest hours: very early morning or later in the evening."

When such timing isn't possible, Farmer advises shortening workouts--instead of 45-minute sessions, maybe go for 20 or 25 minutes--and monitoring breathing. "If you feel the horse's sides heaving in and out, or you see his nostrils flare excessively, it's time to let him walk--not stand still, but walk quietly until his breathing is normal again," she says. If, after about 10 minutes of walking, "everybody else's horses are breathing normally but yours is still huffing and puffing, you may want to have his cardiovascular fitness evaluated--and have your vet check that there isn't some underlying physical problem."

After working, begin cool-down by walking, helping your horse's muscles stay supple while his respiratory rate recovers. Then remove his tack and hose his neck and chest areas first, Farmer says. "The jugular vein is right there (in the neck); cooling that off you cool the blood coming back to the heart, which cools the body internally," she says. "Then hose off the whole body, sweat-scrape him, and hose again. That pulls heat out faster than just hosing and letting water sit on the skin," which heats up quickly, counteracting the desired cooling.

An alcohol bath followed by drying in front of a fan can accelerate heat dissipation; alcohol dries the skin, however, so save this for when a horse has been worked particularly harder than usual.

A horse whose respiration hasn't slowed much despite hosing (if, for instance, the water from the hose is warm, as often is the case in summer) might require additional help. Wrap bags of ice in a couple of towels for five minutes, then spread the chilled towels across the horse's back, says Farmer. Or use towels that have been soaked in ice water to wash him off.

Effective cooling and recovery can be especially difficult, House says, for "horses with longer hair coats that don't shed out completely--for instance, older horses with (the metabolic condition) equine Cushing's disease. Clipping their coats for spring and summer helps ensure that they can be adequately cooled down."

Top Summer Concerns

Before summer heat hits its peak, have a veterinarian conduct a general wellness exam on your horse. "We vaccinate in spring and fall, at minimum; if your vet's already at the barn for that, have her or him take a couple of minutes to listen to the heart, listen to the lungs, maybe also evaluate weight and diet," Farmer says. "Checking twice a year, you'll catch most problems when they're really minor. And if a horse isn't sweating, you can take steps to improve things before the season gets really hot."

The most common heat-related problem Farmer sees in horses is fatigue caused by hard work plus insufficient fluid intake and/or insufficient replacement of electrolytes lost through sweating. The culprit is most likely a distracted human who didn't refill an empty water bucket or replace a salt block. Because, given the opportunity, most horses will correct this problem on their own. "If you provide a salt block with electrolytes, they'll eat what they need to replenish what they've lost," Farmer says. "Or if you hang one water bucket with electrolytes mixed in and another with just fresh water, they'll pick the bucket they need to drink from."

But horses, too, can get distracted, particularly at competitions, drinking less than they need to "because they're busy watching everything going on," says Farmer. Others can become picky about water that tastes different than their usual supply. For a reluctant drinker at a horse show, bring along a couple of barrels of water from home or accustom the horse to a flavoring agent (maybe electrolytes or a capful of honey) in water at home, then mix in the same flavoring at the show.

Another problem--more common in the Southeast, though not unheard-of elsewhere--is anhidrosis. This condition is characterized by an inability to sweat, usually accompanied by high body temperature and increased breathing rate. Because sweating is how the body cools itself, a horse that can't sweat might overheat enough to cause severe internal damage.

The first corrective step for anhidrosis is to adjust workload so the horse doesn't need sweat's cooling effect as often. Farmer also has had some degree of success in treating the condition with a feed supplement designed to increase sweat production; talk to your vet about such solutions. If that doesn't help, she suggests a course of electrolytes delivered via noninvasive dermal patch.

For many horses that cannot sweat, hot-weather riding is out of the question. The physical stress is "too much for their bodies to take," Farmer says. "The respiratory rate will get very high very quickly, and it's not worth the risk." Owners of anhidrotic horses should take a break from riding during the hottest months, especially August, she notes.

Take-Home Message

Keeping any horse healthy and safe in hot weather is a challenge, but one you can meet with knowledge, planning, careful observation, and prompt response to signs of discomfort or struggle. In other words, contrary to the popular slogan, do sweat the small stuff.

About the Author

D.J. Carey Lyons

D.J. Carey Lyons is a lifelong resident of Chester County, Pa. She also has written for USDF Connection, Practical Horseman, Equine Images, and Dressage & CT.

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