How much hay is he getting? If he's getting free choice (or nearly so) hay, then I'd add a big 2qt scoop of alfalfa pellets to each meal, and keep him on 1.5 lbs of rice bran. Alfalfa worked great on my ribby boy.
Peggy, he's been on it since the beginning of November. I started transitioning him to it the 3rd week in October. He's been getting 2.5 pounds a day of the Enrich.
Luvs, he has free choice hay that is out there in round bales for him and the other geldings. My one worry is that alfalfa pellets will make him hot-he was a bit of a nutter when I first got him and he was on a really molasses rich 12% sweet feed.