As I have my three month old pullets/cockerel running around with the grown-ups I have substituted the normal laying pellets with grow crumbles. However as the adult hens are laying I also have a bin of crushed egg shells to make up for the lack of calcium in the crumbles and was wondering about the effectiveness of egg vs. oyster as a calcium supplement. I have read in other posts that most of the shell passes through the chicken without being absorbed so I dry out the shells in the oven and grind them up into grains the size of fine sand in the hopes that more will be 'digested' and absorbed. Will this work? Or should I be giving my laying birds oyster instead of egg shells? The shells she has been laying look OK, but I want to be sure. Once the pullets start laying I will of course be giving everyone lay pellets.