I was given an almost empty box of grapenuts cereal which my family doesn't eat. Would it be safe to feed it to my 7wk and 3wk chicks? Or would they be too difficult to digest? I don't have any grit yet, should I wait till they have it available before I give it to them? Normally I wouldn't even question good cereal (not the sugary/colored stuff) but grapenuts are so hard I wondered if it would be okay. Thanks so much!