Hello Although my hens aren't going to lay yet(but very soon!), I was curious; are there other sources of calcium for chickens instead of crushed oyster shells, egg shells and limestone? I heard of this cuttlebone that is used to supplement other pet birds like parrots(and even crabs) with calcium and minerals; there's lots of them here. Can I use them, or is it dangerous? Here's a pic: Thanks in advance!