We are having a really hard time finding grit for our chickens. The people at the store where we buy our feed have no clue what we are talking about and insist that oyster shells do the trick but I've read that it isn't the same thing. We found one place who knows exactly what we're talking about (finally!) but they only have some during spring/summer. I have seen bags of parakeet grit in pet stores, is this okay to give to our 11 month old chickens as grit? It looks like it's pretty much the same thing?