Anhidrosis is best described as what?

Anhidrosis is specifically defined as the inability to sweat. This condition can occur in horses and can have significant impacts on their health and performance, especially in hot and humid conditions. Sweating is a critical mechanism for thermoregulation, allowing horses to cool down after exertion and maintain their body temperature. When a horse experiences anhidrosis, it cannot dissipate heat effectively, leading to increased body temperatures and potential overheating, which can be very dangerous.

The other options do not relate to anhidrosis. The inability to eat refers to a lack of ability to consume food, which is unrelated to the sweating process. Lack of appetite indicates a horse's reluctance or refusal to eat but does not involve sweat production. Difficulty breathing pertains to respiratory issues, again not connected to the function of sweat glands. Each of these conditions represents different health concerns that do not encompass the specific definition of anhidrosis.