Environmental effects on thermoregulation and nutrition of horses.

Horses are reared in all types of weather. Temperatures as diverse as -40 degrees C to 40 degrees C are tolerated by horses. The nutrient requirement most influenced by cold weather is energy. In cold weather, feeding good quality hays free-choice is usually sufficient for mature horses in good body condition. Grain may have to be fed when poor quality hays are used. Hot weather (greater than 30 degrees C) necessitates heat loss to maintain body core temperature. Horses sweat to reduce body heat. Heat stress can be minimized by feeding diets that reduce the heat increment. Use of grain and fat in the diet, which have a lower heat increment than fibrous feeds such as hays, may benefit horses in hot climates. Wind or precipitation necessitate protection to minimize chilling in cold weather and discomfort in hot weather. However, it is a moot point whether horses will use shelters under these circumstances.