“Must I blanket my horse?” the short answer is “no.” If your horse is healthy with a full hair coat, shelter from the wind and rain, and a good supply of hay then he should not need a blanket. The horse generates his own blanket–a haircoat that is long enough and thick enough to withstand the coldest days of winter. It’s an adjustable covering that flattens against or elevates above the skin, as the horse grows warmer or cooler. Horses also heat from the inside out by fermenting hay in their colon.
Blanketing is necessary for competition horses who are routinely clipped during colder weather to maintain a sleek appearance, reduce sweating, shorten cooling-out time and speed drying after rigorous workouts. Older horses with marked muscle wasting or horses needing equine senior, or other pelleted complete feed instead of hay may benefit from a blanket.
Some horses are blanketed mostly for the owners’ peace of mind and/or convenience (it’s a lot easier to lift off a layer of mud caked onto a blanket than to curry it out of a winter coat). There’s no harm done in blanketing for reasons other than the horse’s health, but in all cases, the addition of clothing increases your management responsibilities. Always check blanketed horses for evidence of sweating or dampness under the blanket, and watch for steam coming off your horse in the morning. These would be indications that the blanket is too heavy for the current conditions.