I've never used that one, but do feed and have success with Select the best Nu-Image.
My hard keepers also get beet pulp @ lunch, I've found that plus a bran mash once weekly keeps them in great BCS[body condition score]
Also by feeding 3x day, I'm actually feeding less volume both per meal and total volume, which is always a good thing for their systems.
You may also, if his kidney function is good, add a little Alfalfa or good legume hay in addition to his grass hay. Mega calories can be added with oils,corn and certain whole grains, but that gets a little tricky with maintaining vit/min balances.