Soon before my chicks began laying I gave them oyster shell in a seperate feeder and they seemed to eat a bit of it every day and that continued up until a week or so after they began to lay. At that time they stopped eating the oyster shell. Their eggs are perfect. Very hard shells on all of them. I feed them layers and give them yogurt and fruit mixed with their own crushed egg shells as treats. It seems that they know when they need calcium and when and if they do, they eat oyster shells. If their bodies are getting enough from other sources, they do not eat oyster shells. Do others of you find the same to be true?