Like most mammals, human beings included, horse’s need a certain amount of salt in their body. Salt is an electrolyte, and acts to attract and retain water in the body, which is particularly important for a horse. Horses tend to lose water in hot weather, through activity and heat, and fail to consume enough during cold weather, as they aren’t keen on the cold water. Obviously, you don’t want your horse to dehydrate, so you need to make sure they have enough salt in their system to properly regulate the water content of their body.