optiflex (sold commonly as zilmax by Merck) is a feed additive that is fed for, generally, the last 20 days in a feedlot. It will increase carcass weights, harvest weights, and provide some bloom. But, I think there is a tissue residue samples and some of the packers are discounting or refusing carcasses fed zilmax. The way it was explained to me is that it causes water retention, particularly in the muscle tissue, which is just water weight that the packers are buying. It will likely do what you want for the added bloom, but I would measure that against where you are sending the calf for harvest.