Good Morning! I have read posts that say don't feed oyster shell until your birds start laying, and I've read posts that say to offer oyster shell when they are near to laying. Mine are about 19 1/2 weeks old. They are not yet laying but I would not be surprised to get an egg in the next day or two based on the behavior of the BR and the BO. So....is there harm in feeding oyster shell to birds that have not yet laid? The purpose would be to make certain that the first eggs were not thin shelled - something I also read a lot of postings about. They are on layer feed. Thanks!