Being a newbie, am I missing something in the care of our girls? We have 7.5(long broody hen story) of our 10 pullets laying eggs and have never offered our girls oyster shell's...are the shell's used for egg production or is it for general health care as well? I have assumed that oyster shell's were for production of egg shell quality. Our girls lay very robust shells and didn't see the need. The area we live in is a river delta with fertile soil and we have many snail shell's in all areas of the chicken runs and they free range our 1/3 of an acre also.