Grit

Grit is small, hard, insoluble stones that chickens swallow and hold in their gizzard, a muscular organ that grinds up food since birds have no teeth to chew with. Without enough grit on hand, a chicken's gizzard cannot break down whole grains, scratch, or fibrous greens efficiently, and digestion suffers even if the feed itself is high quality.

How much grit a flock needs depends heavily on diet. Birds that free range and peck at grass, seeds, and bugs, or that get scratch grains and treats regularly, need grit more than a flock eating only commercial pellets, which are already broken down and easier to digest. Chick grit is sold in a finer size than adult grit, since young birds need smaller particles they can actually swallow and use.

A common mistake is confusing grit with oyster shell, since both are often sold near each other but serve completely different purposes: grit aids digestion while oyster shell supplies calcium for eggshells. Another common mistake is assuming birds with any outdoor access automatically get enough grit from the ground, when many yards do not naturally supply the right size or amount.