Grit: typically consists of bits of granite and small rocks that pass into the gizzard to help break up food. Basically the chicken version of teeth! All chickens, young and old, male and female, should be provided with grit.
Oyster shell: oyster shell is calcium and helps to make egg shells strong. Only hens that are laying should be provided with this, and it should be free choice. Layer feed has calcium in it, but you should also put out a small dish with oyster shell near the feed. The hens will eat what they need. If you do not feed layer or put out calcium you may have problems with egg-bindings and softshelled, or even shell-less eggs. You should not feed layer to chicks because it can cause kidney damage, but I'd say that this is occasional. I've never heard of it happening and I usually give my young birds layer as teenagers. If they do not need the calcium, they will eat significantly less from the feed because they just don't need it.
Oyster shell: oyster shell is calcium and helps to make egg shells strong. Only hens that are laying should be provided with this, and it should be free choice. Layer feed has calcium in it, but you should also put out a small dish with oyster shell near the feed. The hens will eat what they need. If you do not feed layer or put out calcium you may have problems with egg-bindings and softshelled, or even shell-less eggs. You should not feed layer to chicks because it can cause kidney damage, but I'd say that this is occasional. I've never heard of it happening and I usually give my young birds layer as teenagers. If they do not need the calcium, they will eat significantly less from the feed because they just don't need it.
