Grit vs Oyster Shell (Two Different Jobs)
By The Coop Team · Updated July 3, 2026
Quick answer
Grit and oyster shell serve different purposes in poultry nutrition. Grit, an insoluble crushed granite, is necessary for grinding food in the gizzard, while oyster shell provides calcium for egg production. Offer grit free choice in a small dish and oyster shell in a separate dish, never mixed with feed.
Key facts
- Oyster shell calcium supply frequency
- 24-26 hours
- Baking temperature for eggshell substitute
- 250 F
- Grit type for chicks
- fine
- Grit type for adults
- coarse
- Condition indicating calcium deficiency
- thin, wrinkled, or shell-less eggs
Grit and oyster shell look similar but do different jobs. Grit is insoluble crushed granite. It sits in the gizzard and grinds whole grains, seeds, bugs, and coarse forage the bird cannot chew (chickens have no teeth). Any bird eating anything other than pure crumble needs grit, offered free choice in a small dish. Free-range birds pick up their own from the ground.
Types of Grit
- Chick grit (fine) for chicks
- Adult grit (coarse) for grown birds
Oyster Shell
Oyster shell is soluble calcium carbonate. It dissolves in the gut and supplies the calcium a laying hen pulls out of her bones every 24-26 hours to build the next eggshell. Offer it free choice in a separate dish, never mixed into feed, so only the birds that need it eat it.
Do not force calcium on chicks, growing pullets, or roosters. Extra calcium damages developing kidneys. Crushed eggshells baked at 250 F for 10 minutes and crumbled work as a free oyster-shell substitute.
Signs of Calcium Deficiency
- Thin eggs
- Wrinkled eggs
- Shell-less eggs
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