Good info! I have been feeding my hens and rooster layer feed ever since they got old enough (about 9 months now). Does anyone know if we can clean and crush our own oyster shells? I live in the Washington State Puget Sound area and have tons of shells available to me all over the place.
I tried it once with some shells in a plastic bag and hammer and it didn't go well. Perhaps a very tough concrete or thick metal container with some sort of smasher might work.
Though the oyster shell I buy at the feed store almost seems like the outer fringes of an actual oyster shell. It seems that the really dense shell underneath the "frilly ridges" isn't what they sell. When I crushed it up, there were some very sharp pieces...I actually didn't end up feeding it to the birds for fear it might do internal damage.