Regarding protein, just read the label on the bag. Chick starter generally has more protein than layer feed.Thankyou so much for that , I was concerned that it wouldn’t be enough protein etc for the hens and also might affect their egg production.. now that I know that I’ll give my still broody hen some more eggs to hatch ( after she has had a rest )
As @FrostRanger said, the only real issue with hens eating chick starter is that it does not have enough calcium. Poviding a separate dish of oyster shell is the easy fix. Chickens will generally eat the right amount of oyster shell for their own needs: more for the layers, none or very little for the chicks and any roosters or non-laying hens. No, you don't have to worry about the chicks having access to the oyster shell. They don't seem to like the taste until they get old enough to need it.