My girls have been laying now for about a month and a half. I've yet to give them any oyster shells, and they are laying eggs just fine. Recently, I bought a bag of oyster shell, but have yet to give them any. Is it absolutley necessary to add this to their diet? What exactly is it's purpose? Do I just set a bowl out for them to just free feed on this stuff? Also, I seem to have read somewhere of people grinding up the chicken's own eggshells, and feeding them this as a form of calcium. Has anyone any knowledge of this? Thanks so much, I want to keep my girls off to a good start!!