There are two times during the day that a horse will drink the most, within a few hours of sunrise and a few hours before dark. They will drink at other times but not like at these times. Offer the horse loose salt either pickling or table salt. The horse gets a sore tongue from a lick and consequently doesn't ingest adequate amounts of salt. If you can feed hay cubes or pellets it will enable you to reduce the amount of alfalfa. Too much alfalfa can create a calcium inbalance and the horse can develop a conditon called Big Head, for obvious reasons. You can even offer him oat straw. The gut needs roughage but it doesn't always need high quality roughage. One flake of oat straw is ok per day. It does need to be clean quality straw.