Multi flock starter/grower (is non medicated, 22% protein) . You'll then need to offer your hens some extra calcium. Feed back the empty egg shells, and pick up a bag of oyster shell (I can get 50# for $10.) In the winter months, I do not feed layer at all. Keep them on the multiflock for the extra protein.
Depends of the company, Purina and some other feed mfg's do sell a "Multi Flock" feed that is Medicated..
Purina's Flock Raise comes in Medicated and a Non-Medicated, There Medicated Flock Raise contains Amprolium.