What kind of hay is he getting?
I wish my guy would chill out just a little!
I feed my yearling a large flake of alfalfa 2x's a day and nearly free choice bermuda hay (we have no pasture). He only gets 1/2 pound of Strategy, just enough to give him a little scoop of vitamin/mineral supplement.
Basically, it's the alfalfa he thrives on. I try for his diet to be 50/50 alfalfa and grass hay. Alfalfa gives the protein, calcuim and calories he needs to grow and the bermuda helps balance it out and gives him something to much on throughout the day.
I used to feed him several pounds of the Ultium Growth but it was getting expensive and my yearling bounces off the walls, so I cut it out of his diet months ago. But it IS a really good product.
I think the basis of any horse's diet should be really good quality hay. If you get the hay right, then everything else is just supplementing it to make sure he isn't missing any important nutrients.