I have 7 chickens who are laying daily. I get 5 to 6 eggs a day. I am feeding layer pellets and also provide oyster shell. The chickens go out into their pen when the weather is nice but we still have like 2 to 3 feet of snow on the ground. My question is about grit. I have never provided grit just food and oyster shell and treats. My chickens are about 10 months old and have never had grit. Should I be giving them grit?? My chickens also share their coop with 6 guineas.