What kinda steer is he? If he is still putting on frame pouring the fat to him will help to slow the frame down, but wont help in the weight gain issue. If he is still putting frame on and has some true growth left in him, he may just be one that finishes a little heavier than we would like. I always say finish where they will look best for their frame, if he has the frame to be a 1400 kinda steer then that is where he needs to finish. I always feel they do better that way than if you have one that has the frame and needs to finish at that heavier weight and you try to keep em to a lighter weight.
But to answer your question, I think I would turn him out on just pasture or hay for a while and pull him up end of January or so and freshen him up.