© Voice, August 2006
By Sarah Gee

Anyone who has exercised, played, or worked in high heat knows how uncomfortable and exhausting it can be. Whether it’s a high, fluid-sapping desert heat that drains you in no time as you sweat away volumes of fluids and electrolytes, or a suppressive, sweaty, heat-and-humidity combination with air so heavy you feel like you’re swimming through it, high heat makes us feel lethargic, uncomfortable, and sometimes a little ill. Considering how awful it can make we humans feel, with our relatively puny bodies of limited muscle mass, imagine the toll it can take on our equine partners who carry1,000 pounds of steaming muscle and body heat and hair coat around all the time.

Of course, with summer being the height of show and trail riding season, you can’t simply not work your horse. Therefore, you must take it upon yourself to ensure that your horse is in the best condition and adequately acclimated to withstand high temperatures.

Obviously, a fit horse in good health and condition is better able to withstand the ravages of heat. In addition to building muscle, conditioning builds the circulatory and respiratory systems so the horse can cope with the additional stresses of exercising in the heat. The key to conditioning is to work your horse slowly and consistently. Gradually increasing work/rest/work intervals at the running walk or canter is considered a good way to increase fitness and conditioning.

While exercise and workouts can be maintained during periods of high heat, horse owners will need to adjust the time and intensity of the work program and keep a watchful eye on the horse to make sure it’s not overheating. It is best to start out slow when working a horse in the heat.
Begin by just walking them for four or five days and then gradually work up to more strenuous activity. This will help acclimate the horse to working in the heat. Another option is to hold workouts in the early morning when the temperature is lower. Of course, if you plan to show your horse in the heat of the day, you will still need to acclimate him to those conditions. Perhaps the best option is to alternate your work-outs so that one day the horse is worked in the heat of the day and the next he is worked in the early morning and so on. This way, the horse will become acclimated while experiencing less stress. Remember, when working your horse in high heat and humidity, a shorter workout is the stress equivalent of a longer workout under more optimal conditions.
Cooling down a horse in hot weather takes much longer. In the heat, horses don’t recover as quickly from stress. They’ll blow much longer, drink more water, and take longer to cool down their bodily functions and bodily temperatures. Patience and a watchful eye are essential with cooling down your horse in hot weather. Some tips for cooling down a horse in hot weather include putting the horse in a cool or shady area, letting the horse stand in front of a fan or misting fan, and washing the horse down with cold water. Studies have proven there are no adverse affects to treating hot horses with cold water. In fact, hosing a horse down with cold water may be one of the most effective ways of cooling the animal.

So, how do you tell when the horse is cool? Well, generally, a horse that has adequately cooled off will be breathing normally, won’t be sweaty, and will look alert. However, a better way of knowing that the horse has cooled off sufficiently is by monitoring its vital signs.

A healthy adult horse usually has a temperature around 99.5 – 100.5 degrees. Exercise causes the temperature to go up. Many horses’ temperatures will go up to 103 or 104 degrees. This isn’t dangerous, but you’d want to put the horse in the shade and cool him off with some water to make him more comfortable.

Check the heart or pulse rate prior to and right after exercising to ascertain stress. Know what is normal for your horse and how long he usually takes to recover. The normal heart rate for a horse at rest is between 32 and 44 beats per minute.

Finally, in order to ensure your horse’s well being during hot weather it is essential that he have adequate water and electrolytes. In normal circumstances, a horse will drink about eight to ten gallons of water a day. But in hot weather, horses, especially working horses, can lose 11 to 13 quarts of sweat per hour. Therefore, in hot weather horses my need up to 20 gallons of water per day. Obviously, that water must be clean, fresh, and palatable.

Horses lose salt when they sweat so it is important to compensate by adding electrolytes to feed or water. Horse owners should avoid commercial electrolytes supplements that contain a lot of sugar and look for ones formulated for the replacement of salt lost in sweat. Or they can try the following recipe: One part regular salt, one part light salt, and a half part dolomite. Horses that are stalled or corralled and not being stressed or worked hard will not need the same level of supplemental electrolytes as horses in rigorous training.

Recognizing and Treating Heat Stress

• A horse with mild heat stress will take 30 to 40 breaths per minute and have a heart rate of 50 to 60 beats per minute. His entire body will be covered in a film of sweat. He will have more small veins popping out on his body than usual. He will be reluctant to work. He will hold his head down. He will be uninterested in his surroundings. His gums will be darker than normal. He will have a temperature of 102.1 to 103 degrees. To treat mild heat stress cool out the horse as you normally would.

• A horse with moderate heat stress will take 40 to 50 breaths per minute and have a heart rate of 61 to 80 beats per minute. He will have sweat dripping from his neck and between his hind legs. Most of his body will be covered by a road map of bulging veins. He will have no interest in food. He may stumble or lose his balance. His gums will be dark pink or maroon. He will have a temperature of 103.1 to 105 degrees. To treat moderate heat stress, in addition to cooling out the horse, monitor vital signs every 10 to 15 minutes. If they fail to improve in 20 to 30 minutes or if his condition worsens, call your vet.

• A horse with severe heat stress will take more than 50 breaths per minute and have a heart rate of more than 80 beats per minute. Sweat will pour from all part of his body. Veins will protrude over much of his body. He will be oblivious to his surroundings. He may stagger or collapse. He will have dark red or purple gums. His temperature will be over 105 degrees. For severe heat stress getting a vet is imperative because the horse is in danger of heat exhaustion, which is a life-threatening emergency. Monitor and record vital signs every 10 to 15 minutes and report them to your vet. The horse may need intravenous fluids.

References:
King, Marcia, COOL AID: Beating the Heat in Working Horses, The International Equine Journal at www.theequinejournal.com

How to Cool Out a Horse in Hot Weather at www.ehow.com/how_10150_cool-horse-hot.html