If you have a horse that does not produce a good winter coat or you would like to aviod a winter coat you should blanket and this depends on how cold it really gets ( wind chill). If you notice your horse out there shivering, then by all means you should blanket. The object is for one to keep body weight on the horse. If they spend a significant amount of energy keeing warm they will loose a good deal of weight no matter what or how much you feed. As far as the hood goes, well it is a good practice to hood your horse. This is body heat lost otherwise. If you do not have a hood, then at least you should blanket. If your horse does not have a leanto to take cover from the wind and ice, then you really do need to keep a hood on. Horses generally take the cold pretty well. In fact from what I have read, thier optimal temperature is about 40 to 45 degress for the environment.