I read an article recently that suggested feeding chickens their own shells to help add calciuum to their diet. I know a lot of people use oyster shells, but I'm looking for a more sustainable option. This article suggested baking the shells in the oven for 20 minutes at 275 then mashing the shells up and giving it to the birds. According to the article the baking helps to kill all of the bacteria on the shells and changes the taste of the eggs so the chickens do not get a taste for their own shells. What are your thoughts?