I'm sure this has been asked before, so I apologize. I have two Brahma hens who have been laying for a couple of months now. They have a pan of oyster shell in their run, but it's low and I need to refill it yet have misplaced the bag of oyster shell. I have wanted to just feed them their own eggshells for awhile now and have some crushed and ready, but I had a couple of questions about doing that. 1) Is it okay to feed just their eggshells, or do I also need to add oyster shell to the mix? 2) On that note, will they every need an oyster shell supplement? I guess I was wondering if eventually the "cycle" of calcium would get weak and they would need calcium from an outside source. These eggshells will have lots of calcium since they've been eating oyster shell, but if they only eat eggshells, will each egg have less calcium in it since it's being cycled through the chicken? Does that make sense? I may be off base and over-worrying, but I figured I'd find out for sure instead of doing something totally wrong and stupid. Thanks.