You need to feed your horse quality hay, whatever kind is most common in your area. The myths about alfalfa are just that, in places like Washington state alfalfa is the most commonly fed hay. Types of hay include lespedeza, Italian rye, Timothy, Bermuda grass, brome grass, oat hay, etc. you can always mix things up if you like, horses are really meant to eat the same thing all the time. I have fed Timothy, rye, orchard grass, alfalfa, lespedeza and Bermuda. I would avoid round bales because quality usually isn't great but any properly put up hay is fine. You can always have it tested.