Horse Disease Focus - Anhydrosis
Horses and Sweating
The animal most people are most familiar with as a companion is the dog. Dogs do not sweat, and must cool themselves by other means...this is why dogs pant all the time and why they are so quick (for the most part) to jump in the river on a hot day.
Horses do sweat. After a ride, it is normal to find sweat under the tack (in fact, experts can tell whether a saddle fits correctly just by looking at the sweat marks). On a hot day, the horse may also sweat on the neck and shoulder, as well as between the legs and under the tail. Sweating is normal, although excessive sweating may be a sign that the horse is starting to overheat and would appreciate being cooled off.
If a horse does not sweat when it should, however, this can be a sign of a serious problem: Anhydrosis.
Transient anhydrosis is a sign of severe heat exhaustion or heat stroke. If you are working a horse on a hot day and it stops sweating, this is a very bad sign.
The horse must be immediately rested and cooled down as quickly as possible. The best method is to hose the horse down, then scrape the water off and do it again. The horse should also be offered slightly warmed water with electrolytes. If equine electrolytes are not available, adding some gatorade to the water is perfectly acceptable and effective. Most horses don't seem to mind the taste...or at that point they're thirsty enough not to care.
Note that this condition also affects humans. Always carry water with electrolytes on longer trail rides. Emergen-C or similar electrolyte powders are very useful to keep around the barn, as is gatorade.
Chronic anhydrosis is a defect that causes the horse to progressively lose its ability to sweat. It only affects horses that live in hot and humid environments. It is probable that the defect exists in cooler and dryer climates but remains asymptomatic as those horses are under less heat stress.
Other than the obvious inability to sweat, horses with anhydrosis will demonstrate a dry coat and may lose hair on the face, rear end and legs. They may try desperately to cool off, for example by standing in streams and ponds. It is not normal for a horse to pant (unlike a dog) unless the temperature is very high, and even then it is rarely seen. The horse often has a depressed appetite.
There is no specific treatment for anhydrosis. Some horses benefit from regular electrolytes and may regain their ability to sweat. The condition can be managed by reducing work at hot times of the year and the day and washing the horse off after work. (All horses enjoy and benefit from a cold 'shower' after work on a hot day).
The horse will need to be provided with plenty of shade. Work the animal in the early morning or late evening. If showing, you may be able to get an early or late 'ride time' in some disciplines, but some anhydrotic horses may not be able to sustain a show career. Some horses recover spontaneously, others may remain anhydrotic for the rest of their lives. In some cases, the best treatment is to move the horse to a colder climate, but this may not be feasible.