How long does it take for calcium to start helping with thin shelled eggs? I have one chicken out of ten that started laying, today she laid her 4th egg and the shell was thin and had a hole in it. I put oyster shell in the coop yesterday and tried to give her some by hand and she doesn't seem interested in it. I tried giving her some layer pellets and she only picked at them a little bit. I cave calcium supplements that I have had around, would it be okay to give her some of that ground up on some leafs of lettuce?