I have been offering oyster shell to my laying hens since they began laying about two months ago. I have been buying the Manna Pro crushed oyster shell which is about $5.99/5lb bag at the local Co-op. A few days ago I visited a feed store with my sister and bought what I thought was oyster shell in a 50lb bag for $7.99--they said it was oyster shell. It's called Tuff Shell. So, I get it home & start reading the bag--this is what it says: Tuff Shell: Feed Grade Calcium (front) The back reads: Calcitic Limestone Typical Dry Weight Analysis CA (Calcium) 38% It also has a warning: [This product contains small amounts of crystalline silica, a common mineral found in natural sands and stones. Excessive inhalation of respirable silica dust may cause cancer or lung disease. Avoid breathing dust. Wear approved respirator in dusty areas.] Now, this just doesn't sound good to me. I'm even confused why I'm feeding them limestone....?? Seems like that is just grit--it looks like grit, not oyster shell...which is what they said it was. Not. Do any of you guys use this? Additionally, I supplemented them with crushed egg shells yesterday. But, I'm not sure how much to provide or how to prepare it. If I do this, I've heard and read that you should bake the shells--is that really necessary? Any help here would be appreciated!