The horse's skin and coat are important to your horse's overall health and require proper nutritional support. that's why so many of us feed a hoof supplement (hooves, coat and skin require basically the same nutrients). But, if calories/nutrients are in short supply, the horse's body will send them to more critical organs first. To combat this, in the winter, feed your horse about 2 lbs. of hay more for every 10° the temperature drops below 40°, which is the horse's critical temperature.