Hens ~ I used to feed the medicated Chick Starter too, and fed it until they were 6 weeks old. I don't use it any more, as I have read lots of posts that say the low dose of antibiotics builds up in their systems, but is not enough to knock out something like Cocci. Then when you do need to use antibiotics, they have a somewhat resistance to them, due to the low buildup of the antibiotics in the feed. I just start mine right off on Chick Grower feed, non-medicated, and so far, I've had no incidence with any diseases here.