First, make sure he isnt' sick. Does he act sick? Does he look sick? Use your common sense or call a vet. If he is just not eating, there can be a couple things you can try. If he has been a good eater and is just off his feed, then as tough as it is, back off a few days and just feed him good grass hay. A bunch of it. then start adding feed back in to his diet. Add a high fat supplement. I have used Purinas Power Fuel and it works well. You can add Glu-coate to it also or just add some molasses to his feed to make it more attractive. Molasses is a good energy source that is not a fat product. Call one of the feed nutrionists at Purina or Showmaster and talk with them. They will give you advise also. Bran will add cover as will barley and cooked corn. It just depends on what your calf will eat. Probiotics never hurt either. At best you will only get about 75 to 100 lbs on him and that is pushing it. Good luck.