How much grit should I be giving to my chicks? They are mostly on the medicated crumbles but I give them just a few mealworms or some other little treat in the afternoons. Should I just leave the grit in the pen all the time or just put it down for a little while when I'm out there with them. Also, every now and they I will see one slurp down a tiny piece of shavings. Is this ok? Thoughts?