I'm with the group that says complete layer feed is all that is needed. That comes from my friend that has a Ph.D. in Poultry Science and just retired from USDA. He also said that feeding oyster shell isn't a bad thing, but is usually not needed. But there are always exceptions. He keeps some around for those exceptions. He has about 200-300 different chickens at any one time and is a full time farmer, now.