Also, clean out the stall, and check it for needed repairs and remove risks. After the housing is in shape, check your horse. It should have enough body fat to insulate against winter's cold wind, rain and snow. You can visually evaluate body condition. Your horse should have at least a BCS of 5, which means you can't see the ribs but can feel them if you apply slight pressure.
Horses add body fat from front to rear and top to bottom.
Evaluate fat deposits in their necks, withers, covering over their rib cages and croups and around their tailheads. Feel horses to evaluate body condition in winter due to their heavier winter haircoat. Often you can't accurately evaluate a horse's body condition by only looking. And continue scoring your horse each month in winter. If your horse has less than a 5 body condition score, increase its energy.