you are a gambler either way. If you are taking all the way to fat, go ahead and put them on corn and sell when they are ready to you.  If you are planning to put 150-200 pounds on them and then sell them, do not bring them up on feed and ruin the finishing for someone else. Take most of the grain away, grow them properly so they can reach a 1600# weight at finishing so the feeder can make it work also. We are all in this together.