Anhidrosis

Unfortunately, it is that time of year again...it is hot, humid, and just plain miserable here in Florida. But what’s even worse than dealing with the intense heat is dealing with a horse that has stopped sweating. Anhidrosis is common problem that has no quick and easy cure. Horses stop sweating for different reasons, and they respond to treatments differently. Personally, I have dealt with this issue in horses on my own farm, and my management approach is multi-faceted. Since I never know what a horse may respond to, I just try everything I think may have a reasonable chance of success!

Before I outline my management approach, I must stress that if you suspect your horse is anhidrotic, please contact your veterinarian for an exam. There are many conditions that can alter a horse’s ability to thermoregulate - some that can be easily treated and some that are very serious. Also, keep in mind that an individual horse’s sweat production can vary, and there is actually a test that can be performed to confirm whether or not your horse is truly anhidrotic. There are also reports that anhidrotic horses often have high circulating levels of epinephrine, meaning that there is some underlying stressor (i.e. pain). So, call the vet first.

Managing the anhidrotic horse:

1) One-AC – Start supplementation with the commercially available supplement “One-AC” according to package directions. This is a powdered supplement that contains vitamin C, L-tyrosine, and B vitamins. Tyrosine is a precursor to dopamine and may help re-sensitize sweat gland receptors. The success rate is variable and reported to be between 30 – 80%. Best results are achieved when supplementation begins before the weather gets very hot.

2) Reduce heat stress – this is very important, especially during the first 2 – 3 weeks. This includes stalling during the hottest part of the day (if the barn is well-ventilated and cooler than being outdoors) with multiple fans to maximize air circulation. Consider installing a mister or put a sprinkler outside in the paddock to provide some “artificial sweat” that will help with evaporative heat loss. Frequent hosing during the day will also help reduce the heat load. All strenuous exercise should be stopped, and if the horse must be worked, only do it very early in the morning or late in the evening when the weather is cooler. The theory is to try and “re-program” the horse’s thermoregulatory mechanism by taking the stress off of the over-stimulated sweat glands.

3) Electrolytes – insure the horse is receiving adequate Na, Cl, K, Ca, and Mg in the diet. If you are feeding a fortified concentrate feed at the recommended levels paired with plenty of good quality forage, then all you need to be concerned with is NaCl. You should supplement 1 – 2 oz (2 – 4 Tbsp) of plain white salt or a commercial electrolyte supplement every day to provide the necessary NaCl (beware that many contain more sugar than salt).

4) Overall diet – be sure that the horse is receiving a balanaced diet and insure he is not consuming excess protein (>25% protein in the total diet). This scenario would probably only occur if a horse was eating a high proportion of alfalfa/legume hay and a large volume of concentrate feed on a daily basis. If the horse has a high calorie requirement, feeding a high-fat diet may help to reduce “metabolic heat”.

5) Acupuncture – at the University of Florida, clinicians are now utilizing acupuncture as a treatment for anhidrosis. I have seen it work. The key is to find a qualified and experienced DVM who is trained in acupuncture to treat your horse.

6) Dark beer – sure, why not? 1 bottle or can of dark beer (i.e. Guinness) per day for 6 days (that’s one six pack). Dark, unfiltered beer actually contains B vitamins and antioxidants, which could potentially be the reason for those anecdotal success stories you hear about feeding beer to horses. Hey, it can’t hurt…I just pour it over the feed, right after I take a big swig (for testing purposes only)!

The only proven “cure” for anhidrosis is to move the horse to a cooler and drier climate. Unfortunately, this is not always a convenient option. But if a horse is very severely affected, it may be the only choice that is right for the horse. In the majority of cases, though, anhidrosis can be managed successfully if you pay close attention to the horse and are careful to keep him comfortable when the weather is especially unbearable.