Story and photo by Leigh Ann Matthews
Oklahoma summers can be brutal. High temperatures combined with high humidity can result in triple-digit heat indices. Sweat cannot evaporate easily, leaving us hot and sticky. Our bodies must work harder to cool off, resulting in excessive sweating and increased respiration. This can cause low energy and lethargy — not only in humans but also in our equine friends.
Horses, unlike most other animals (dogs, cows, pigs, etc.), have sweat glands throughout their skin, and therefore they sweat much as humans do. The glands enable the horse’s “evaporative cooling” mechanism, which helps keep them from overheating in hot weather. Horses also rely on the dilation of capillaries to help keep them cool.
According to EQUUS magazine, when a horse exercises, the amount of internal heat generated by muscles increases. The capillaries become dilated so more blood will be sent to the skin. When the horse’s exercise generates internal heat, the excess heat must be dissipated more quickly. The horse will begin to sweat when he continues to work to the point that the capillaries can’t keep up with the heat he is generating.
Watch for Anhidrosis
Anhidrosis, a rare condition in which the body produces little or no sweat, occurs in animals in hot, humid regions but can occur anywhere during heat waves. Horses can develop it quickly or gradually, and studies have not revealed age, breed, sex, or color predispositions.
The most common signs of anhidrosis are increased respiratory rate and the inability to cool after exercise or in high ambient temperatures. Affected horses might produce only minimal sweat, but others in the same circumstances might be drenched or even lathered.
Many horses resume sweating when the temperature lowers significantly for several consecutive days, but others might not. Chronic cases might never improve unless the horses are moved to a cooler environment.
Anhidrosis is most common in performance horses but can also occur in others with much less demanding physical activity. Horses with very little physical demands can also experience the condition as well as those kept in lots or paddocks with no shade.
It is advised to keep “nonsweaters” stalled or in shaded paddocks during the day with fans, misters, or sprinklers to help keep them cool. They should have constant access to cool, clean drinking water and possibly electrolytes or salt mixtures.
As always, it is best to consult your veterinarian before implementing a treatment plan. Commercial products might be prescribed along with environmental management.
Act Quickly with Heat Stress
Heat stress is a life-threatening condition that develops when a horse can’t cool down enough by sweating. If his core temperature reaches 104 degrees, his metabolic system might be affected, and if the temperature reaches 105 degrees or higher, his organs and circulatory system might begin to shut down.
Warning signs include thick, sticky sweat; discolored and/or dark gums and mucous membranes; weak, elevated, irregular pulse; depressed stance with low head; and rapid, shallow, or deep gulping breathing.
Quick action is needed to save the horse’s life — call your veterinarian immediately, and start to bring the horse’s body temperature down. Move him to shade, drench him with the coldest water available, scrape him dry and repeat, press ice or cold packs against his head and throat, and encourage him to drink.
Don’t administer an electrolyte paste because forcing him to swallow might stress him even more. You could offer him a bucket of water with dissolved electrolytes, but provide a bucket of plain water too.
Keep Animals Safe in Hot Weather
If your horse works through the hottest months, keeping him fit and in condition for his job will help prevent problems. Hosing down before and during rides is also a good idea. When water isn’t available, allow breaks for resting and grazing — lush grass contains as much as 90 percent water as well as electrolytes. Avoid work during the hottest part of the day. When heat and humidity are both high, postpone activity if possible until conditions improve.
During summer months, always provide shade and cool water, not only for horses but for other animals too. Water in tanks positioned in the sun can heat up substantially during the day, so animals might not drink as much as needed. If you can’t move the tank to a shady spot, add bags of ice several times a day to decrease the water temperature.
When it’s hot out there — take care of yourselves and your animals!
