Grower/Grown-Up Chicken Grit (6+ Weeks)Why do chickens need grit? Chicken Grit is necessary in a chicken's diet for the healthy development of a chickens gizzard. The gizzard aids in digestion, & allows for maximum nutrient benefit from whole grain feeds. Made up of insoluble crushed rock, grit remains in the birds gizzard to help with digestion and grind food as it passes through. Grit comes in various sizes for different birds depending on size and age. Just like chickens eat tiny rocks