Hot! Hot! Hot!

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The lazy days of summer may mean pools, hammocks and lemonade to some, but to horse people it means sweat, more sweat and even more sweat. Working and competing in the heat can be difficult and at times downright dangerous to both horses and humans.

Under harsh conditions it is important to pay attention to your own body as well as your horse’s, so that neither one becomes ill. And even though we are different creatures, horses and humans both have the same basic physiological responses to extreme heat. Children, the elderly and unfit people are most susceptible to extreme heat, as are horses that are sick, geriatric, unfit or heavy-coated.

When We Heat Up

When the seasons shift from winter to spring and then summer, the horse acclimates by increasing blood flow to the skin, decreasing fat layers and shedding the hair coat. Acclimating from cold to warm takes time, depending on the horse’s (and your) workload and fitness level. During exercise, energy is produced by muscle metabolism, and about 80 percent of that energy is released as heat. In hot weather, the horse’s thermoregulatory system must transfer that heat to the environment to prevent excess accumulation. The faster and harder a horse works, the more heat is produced. When the temperature is really high, the horse isn’t fit or is working extremely hard, the horse can’t release enough heat and becomes overloaded. In the most serious cases, it can cause collapse and heat stroke due to lack of oxygen to the brain.

Sweat is the primary means of cooling both horse and human. In extremely hot weather or under intense exercise, the horse needs to expand blood volume to accommodate sweating. In a dry, hot environment, evaporative cooling is good, but you can dehydrate very quickly. On the other hand, high heat and humidity cause slowed heat loss because the air is already saturated with water. Sweating is therefore less effective. Once dehydrated, a horse or person overheats faster than a hydrated one, because less fluid is available for sweating and the body is not able to move heat to the skin surface as well.

When Trouble Occurs

Lethargy, rapid pulse, heavy breathing and a temperature over 105° F are signs that a horse is in trouble. Here is another situation where knowing what is normal for you and your horse will tell you a lot about the situation.

Generally speaking, in people aged 11 and up, the resting heart rate is 60 to 100 beats per minute (BPM), or 40 to 60 BPM in a well-conditioned athlete. The normal respiration rate is 12 to 24 breaths per minute and normal temperature is 98.6° F.

In horses, the resting heart rate is 35 to 45 BPM. It could go up to 80 to 100 BPM immediately following exercise, but within 15 minutes, it should be 40 to 50 BPM. Resting respiration rate is 10 to 20 breaths per minute. A hot horse will breathe rapidly, but that isn’t a bad thing. A high respiration rate of 120 to 140 breaths per minute improves evaporative heat loss through the respiratory tract. However, it should drop to 60 to 80 breaths per minute after the first 10 minutes. Rectal temperature in the horse is typically 99.5° to 101.5°. It is not unusual to see a horse’s temp go up to 104° or 105° in very hot weather. However, it should come down within 10 to 20 minutes after exercise. If it stays above 105°, heat stress is a definite concern.


Once a person becomes dehydrated, the answer is drink, drink and drink some more. Try to move into a cool, shady place. Take off any excess layers of clothing and use cool water or even ice to decrease body temperature. If the person is slow to recover, medical attention is necessary.

Dealing with a horse is similar. According to Robert Lee Godman, DVM, MS, when a horse suffers from heat stress, treatment includes removing all tack, blankets, etc., and dousing the horse with cold water. This causes blood vessels in the skin to constrict, and blood volume returns to the core circulation. Scrape off the excess water and repeat until the horse has fully recovered. Contrary to common belief, there are no adverse affects to treating a hot horse with cold water. It is also helpful to move the horse into the shade and in front of a regular or misting fan. With the exception of racehorses, it is also okay to let a horse drink after exercise. They can consume one to two gallons of water in the first 15 minutes. Finally, it is always wise to have a vet check the horse to make sure the horse has fully recovered and to see if damage has been done to any internal organs.


Keeping you and your horse from overheating first involves acclimating to the warmer weather. Fit horses more easily adapt to changes. If you are shipping a horse from a cool climate to a hot one, allow two to three weeks for the horse to get used to the change. “Heat stress can occur even in very mild temperatures if the horse’s body is still set to conserve heat instead of releasing heat,” says Godman. When it’s cold outside, we typically think about warming our horse up longer, but it’s still important to warm up and let the horse stretch his muscles even in hot weather.

Most prevention techniques involve good common sense. Drink plenty of water before, during (if possible) and after a workout. Electrolytes are important for horses and humans, but be aware that some products for both humans and horses contain a lot of sugar. You can add electrolytes to the horse’s feed or water, but if you add them to water, make sure you also offer an unaltered bucket of water; some horses simply won’t drink the altered water. Don’t overdo the electrolytes; it is likely that only horses in very hard work or in really hot weather need electrolyte supplementation.

Lighten the exercise load when it gets really hot. Research at Ohio State University has shown that shorter work in hot weather is of the same intensity as longer work in moderate temps. They also found that horses handle high humidity with lower temperatures fairly well. This is the typical situation in the morning, when the solar radiation is less. If you know you must compete in the heat of the day, alternate your work patterns between mornings and afternoon. Turning your horse out during the day is okay as long as plenty of clean cool water and shade is available.

If you own or run a facility that offers lessons and shows, try to move your lesson times to mornings and evenings. An indoor arena may provide shade, but unless it is well ventilated, it will become stifling. You may be able to hold small schooling competitions in the evening, but many shows are simply too big to avoid the heat. In this case, schedule the most demanding classes for the cooler parts of the day. Make sure plenty of water, ice and cool towels are available for riders, and that a trained EMT is available. (This author once received medical attention for heat exhaustion from an EMT at the end of a 2-day show during a hot, Kentucky summer. You may not think you’d ever use one, but helping even one person more than justifies any cost.)

At the end of the day, if everyone stays patient and uses common sense, they will all keep their cool.