anhydrosis

    You are probably thinking, "An-hy-what?!", but don't worry, I'm here to tell you what it's about. Anhydrosis is just a fancy name for "no sweat." Your horse is unable to sweat, putting him at high risk for heat stroke. This occurs usually in horses who are transported to hot climates, and worked before they have a chance to adapt to the heat. However, it can still happen to any horse, whether they've been moved or not.
     Stress if the biggest factor in this problem. If a horse is being worked in humid, hot weather for a long period of time, the stress of performance can build up and become Anhydrosis.
     So, in order to prevent your horse from obtaining anhydrosis, avoid shipping your horse from a cool climate to a hot one. But if you must, then allow 2 days or so without work for your horse to adapt. When working in hot weather, do not do so for extensive periods of time, lest you wish to run the risk of your horse developing Anhydrosis.