Ok, What's the difference and when is it given? I have Scratch Grain, Chick Grit and Poultry Grit. I can assume Chick Grit is for chicks(duh). But what about the others? Also about Whole and Cracked Corn? From what I have been reading, Whole Corn should be given during the winter months for warmth. But what about cracked? When should that be given?