There are some important factors to consider when caring for a horse in hot weather. Just like a human, a horse is affected by hot, humid weather: decreased appetite, sluggishness and increased need for water intake. Just like a human, a horse benefits from shade and a cool breeze. If these are not available in a pasture or paddock, then keeping your horse in during the day might be the best option, turning the horse out at night.
One factor that contributes to the well-being of the horse during the hot weather is the weight of the horse. An over-weight horse has a harder time keeping cool because of the insulating layer of fat. The excess fat interferes with the natural cooling system and it increases the amount of food necessary to maintain the horse’s energy level. More food means more body heat production. This causes heat stress in hot weather.
It is important to keep your horse at a body weight that will meet its performance needs. Feed intake requirements change during hot, humid weather due to the metabolism of grains, protein and fat. Energy from the diet is needed to maintain body weight in both cold and hot weather. However, during hot, humid weather, the horse’s appetite and therefore, feed intake, decreases. It’s body weight will decrease as well. In order to maintain body weight, the diet should be high in energy-dense foods which produce less body heat. Fats are higher in energy density than grain mixes (carbohydrates) and produce less body heat. Grain mixes produce more body heat and have less energy density. Thus, the horse needs more energy- dense food so that it will maintain its performance needs with smaller quantities of feed. The diet should be highly palatable so that the horse will be encouraged to eat in hot weather. The dietary energy density can be increased, and heat produced from the diet decreased by decreasing fiber content and by adding fat (plant oil or animal fat). Adding fat to the grain mix increases the diet’s energy-density. A high-fat diet also decreases body heat production. This can reduce heat stress in the summer and leave more energy available for body use.
It is critical during the hot weather that there be an adequate supply of water available as well as shade. The horse’s water need can increase as much as four times the normal water intake. Salt will increase the horse’s desire for water and replace minerals lost through sweating.