Not Breaking a Sweat: Anhidrosis in the Horse

Nokota_Horses_croppedWe’ve had our fair share of hot days this summer in North Carolina. Although it’s mid-August, we still have several more weeks of hot and humid weather before we see some relief. Just like people, horses produce sweat in the hot weather to help thermoregulate their bodies. However, some horses living in warm climates like the Southern United States suffer from a condition called anhidrosis: the inability to sweat appropriately. On days when the heat index is over 100 degrees and most horses are drenched in sweat, a horse with anhidrosis will have little to no sweat production. This results in an elevated body temperature, and puts the affected horse at risk for heat stroke.

The symptoms of anhidrosis include a dry hair coat, rapid breathing rate (even at rest), elevated body temperature, and exercise intolerance. Anhidrosis can affect any horse, whether they were born and raised in a warm climate or are new to the area. In some cases, a horse will sweat at the beginning of the summer, only to stop sweating or have less sweat production when we reach the hottest part of the season. The exact cause is unknown, but may be related to over stimulation of the sweat glands by stress hormones. Fortunately, there are management strategies and treatments that we have to help these horses cope with the hot weather and stimulate sweat production.

There are several commercial supplements available that are used to stimulate sweat production in horses with anhidrosis, including “ One AC” and “Let Em Sweat”. These can be added to your horse’s feed each day, and typically results are seen in 10-14 days. Another option is to add a bottle of beer (that’s right, beer!) to your horse’s feed. This is an old horsemen’s secret, and believe it or not, it does work for some horses. The darker the brew, the better! Acupuncture has also proven to be helpful in stimulating sweat production. Horses suffering from anhidrosis should not be exercised, especially during the warmest parts of the day, until their sweating returns to normal. These horses should be kept inside or in the shade during the day, ideally under fans. Cold hosing or using ice baths can help provide short term relief and lower the body temperature in a horse that has overheated. In rare cases, if treatments aren’t successful, a horse may have to be relocated North where there are cooler temperatures.

For horses that have shown signs of anhidrosis in the past, it is a good idea to begin these treatments during the early part of the warm season (around April or May), and continue them through the summer to help maintain sweat production. This time of year, it’s imperative that owners, riders, and trainers keep a close eye on their horses to make sure they are tolerating the heat. On a very hot and humid day, a horse should be sweating under their mane, along their chest, and in their groin area. Check on your horse during the heat of the day and make sure that their breathing rate at rest is at or below about 24 breaths per minute, and their body temperature is less than 101.5 degrees Fahrenheit. As always, provide plenty of fresh water and shade. If you are concerned that your horse is not sweating enough, please call us right away and we can discuss a management plan with you.

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