for chick coop

Even backyard chickens on a diet of good-quality layer feed need two very necessary supplements: grit and oyster- or eggshell.  Grit is basically coarse dirt, small stones or pebbles, which is stored in their crop and helps them grind and digest anything they eat other than commercial feed, and the oyster shell or egg shell provides additional calcium that they need to make hard shells on the eggs they lay.