Ok, i realize that this may be a really dumb question, but I have to ask to make sure I am doing the right thing for my girls. I understand that chickens do not have teeth and that when outside they pick up pieces of grit, dirt, rock, etc and that this goes to their crop, then food goes to their crop and gets ground up with all the "Stuff" in their. So I guess my question is.......if my girls are in their coop pretty much all winter and the ground is covered with over a foot of snow from Dec.-Mar. do I need to put grit, rocks in their coop? Sorry if this is stupid, I am just unsure how often they need to do this. Any info would be helpful. Thank you.