The problem with letting them graze all the time, and even have hay is that if their teeth are bad, or non-existant, then they have trouble chewing the grass/hay and can get a big ball in their mouth and choke on it. Watch your horse eat. If he is dropping a lot of feed when he eats, get his teeth checked and floated if necessary. When you get his teeth checked, then you can also find out if he has enough teeth to eat properly. When you watch your horse eat, if he is dropping "balls" or "wads" of grass/hay then he probably doesn't have enough teeth to eat it properly. We have 2 right now like that. A 28 y/o TB and a 22+ QH neither one can have hay, so they are on a complete feed. Good luck.