Use a weight tape to encircle his heart girth. Record his weight and monitor it frequently. A long winter coat can be deceiving. Hay is the mainstay of any horse's diet. Alfalfa hay which has higher protein, three times the calcium and more vitamins than grass hay, is often fed to young, growing horses and lactating broodmares.
Good hay is free of mold, dust, and weeds and has a bright green color and a fresh smell.
It is leafy, soft, and dry but not brittle. Feed about 2 pounds of hay per day for every 100 pounds of body weight. Feed hay by weight not flakes. Young horses, horses in hard work, pregnant mares, and mares with foals usually need grain and supplements. Corn has a very thin covering so does not provide much fiber but provides twice the energy content as the same volume of oats.