Brooks Lab: Anhidrosis in horses may have genetic component

Many genetic problems have been identified in horses in last few decades. One of the greatest examples is HYPP, hyperkalemic periodic paralysis, traced back to a single Quarter Horse sire, Impressive. Back in 1992, researchers developed a DNA test capable of identifying horses carrying the gene for HYPP and have attempted to eliminate the disorder through responsible breeding. Now researchers are investigating  to see if a similar approach could be utilized to reduce or eliminate other diseases of horses, such as metabolic syndrome, OCD (osteochondrosis dissecans), heaves, or even anhidrosis.

Experts at the Brooks Equine Genetics Lab at the University of Florida are currently looking for a genetic link in horses affected by anhidrosis. Samantha Brooks is a UF Genetics Institute faculty member.

Horses rely on sweating to control their internal body temperature, especially when exercising in hot and humid conditions. In fact, about 60-65% of excess heat generated by a horse’s body is released through the skin. The remainder is either lost through the respiratory tract or stored in the body. Horses with the inability to sweat can’t dissipate heat, and their chances of developing heat stroke increase dramatically.

Recognizing anhidrosis is usually fairly obvious, especially if your horse is the only one in sight sans sweat. Horses with heat stroke:

• Can appear weak and disoriented;
• Have shallow and rapid breathing (panting);
• May develop muscle tremors or spasms; and
• In some cases, can collapse, appear to be having a seizure, or even die.

“Anhidrosis is a frustrating condition because it can appear suddenly or develop slowly over time. Only a fraction of horses are completely anhidrotic, whereas others are able to sweat to some degree but not as effectively as they need to in order to cool off,” Kathleen Crandell, Ph.D., an equine nutritionist for Kentucky Equine Research shared.

Treatment strategies usually only include management changes. Anhidrotic horses generally must be moved to a cooler climate, have cooling fans, and only be exercised in optimal conditions, such as low humidity and temperature.

“Dietary changes may also benefit horses with anhidrosis,” advised Crandell.

For example, some advocate using an electrolyte supplement such as Restore SR (available as Restore in Australia) or offering diets lower in protein and higher in fat. Such diets produce less heat, ensuring, of course, those rations are not deficient in amino acids (the building blocks of proteins) or roughage.

Considering the dearth of treatment options, lack of a cure, and strong suspicion that anhidrosis is genetic—the odds of anhidrosis are 22 times higher in horses with a family history of anhidrosis—Laura Patterson-Rosa, D.V.M., started searching for the genetic cause of anhidrosis to help eliminate it from the equine population, much like HYPP. To achieve this goal, Patterson-Rosa requires 200 samples submitted from owners of anhidrotic horses or offspring of anhidrotic horses by December 2016. For more information on anhidrosis and to submit samples, visit the Brooks Equine Genetics Lab website.

This article originally appeared at Kentucky Research News