If this horse is off the track then he likely has ulcers. He should be getting about 20 lbs of hay. What does he have for salt? If a block, leave it in his stall but offer loose salt as well. Pickling salt from the grocery store works nicely. Horses do not ingest enough salt from a lick. He needs to be turned out. Horses reguire movement to assist the gut with digestion. Invest about $10 in a small mesh hay net. This will force him to nibble at his hay and this will improve digestion, rather than him bolting it down. He won't be standing around for hours with no feed. Horses spend about 18hr day eating and he should be too, The net will extend the time his hay lasts. Get two and hang in opposite corners of his stall. He'll walk back and forth.