We are getting closer and closer to introducing the pullets to the big-girl flock. Our big-girl flock is given oyster shell as a supplement because we buy Purina flock raiser to feed the chickens and Guinea fowl. Now, I've heard extra calcium can be a very, very bad thing for young birds, so I'm wondering a couple things before we go ahead with our introduction plans. First of all, the pullets are about 13 weeks old. I'm figuring (at the rate we're going ) they probably won't be introduced to the big-girl flock at least until they hit 14 weeks old. Is this too young for them to be eating oyster shell? Second of all, if they are too young, what is the absolute youngest age I could risk the pullets eating the oyster shell? They're reaching the point where they need more room than the grow-up pen that they're in, plus it's becoming a pain for us to move the pen around to give them fresh grass. And I apologize if y'all are sick of answering these questions, but once again my searches haven't come up as conclusive as I would have liked for my situation.