we have used Purina Impulse or intimidator in past years and we were happy with it. Also, purina makes different levels of show bloom/top dress. one for show wethers that need to put on weight, one for wethers that have too much fat on them.
We have also use Show-rite Glen Marten feeds, they have 3 levels to their feed. You move up on the levels as you get closer to the fair. I personally like the purina better. Those are really the only two in our area, other than a couple that the local feed mill makes. I have not used those.
They are both 20 to 21 dollars a 50lb bag.
If you are more mid-west. Then you have a lot more options.