Grit for chickens is small, hard material (usually crushed stone or shell) that birds swallow to grind food inside their digestive system. Because chickens don’t have teeth, they rely on grit stored in a muscular organ called the gizzard to break down tough foods like whole grains, seeds, and grass. There are two distinct types, each serving a completely different purpose: insoluble grit for digestion and soluble grit for calcium.
Why Chickens Need Grit
A chicken’s digestive system works nothing like a mammal’s. Food travels from the crop (a storage pouch in the throat area) down into the gizzard, a thick-walled muscular stomach. The gizzard contracts powerfully and repeatedly, and any small stones inside act like a set of grinding teeth, crushing food particles so nutrients can be absorbed further along the digestive tract. Without this mechanical grinding, harder foods pass through partially undigested, meaning your birds get less nutrition from what they eat.
When chickens free-range, they naturally pick up small stones and pebbles from the ground. These stones get softened by stomach acid before the gizzard muscles grind them into progressively smaller pieces. They stay in the gizzard until they’re worn down small enough to pass through, at which point the chicken needs to pick up fresh stones. Confined chickens that don’t have access to bare ground can’t do this on their own, so they need grit provided for them.
Insoluble Grit: The Digestive Kind
Insoluble grit is typically made from crushed granite or flint. It doesn’t dissolve or break down chemically in the digestive system. Instead, it sits in the gizzard and physically grinds food as the muscles contract around it. Think of it as the closest thing a chicken has to teeth.
This type of grit is essential any time your flock eats whole grains, cracked grains, scratch mixes, kitchen scraps, grass, or insects. If your chickens are eating exclusively a formulated pellet or crumble feed, those feeds dissolve quickly enough that insoluble grit isn’t strictly necessary. But most backyard flocks eat at least some treats, forage, or scratch alongside their main feed, which means they need access to insoluble grit.
Soluble Grit: The Calcium Kind
Soluble grit dissolves inside the bird’s digestive system and provides calcium carbonate, the mineral that forms eggshells. It’s usually sold as crushed oyster shell, crushed mussel shell, or limestone granules. This type serves a nutritional purpose rather than a mechanical one.
The calcium demand on a laying hen is substantial. An eggshell is almost entirely calcium carbonate, and hens that don’t get enough calcium produce progressively thinner shells before egg production slows or stops altogether. Severe calcium restriction causes a general decline in body condition beyond just shell quality. Oyster shell has long been the standard calcium supplement for laying flens, with crushed limestone as the most common alternative. Non-laying birds (roosters, chicks, and pullets not yet in lay) don’t need soluble grit.
What Happens Without Grit
A chicken without access to insoluble grit that’s eating whole grains or fibrous plants can develop crop impaction. The crop is where food is stored before moving further into the digestive system, and impaction happens when a mass of material, often tangled plant fibers, gets too large to pass through. It creates a hard, swollen lump at the base of the bird’s throat and the chicken stops eating normally. Providing grit is one of the standard recommendations for preventing this condition.
Poor digestion also means poor feed efficiency. Your chickens eat the same amount but extract fewer nutrients, which can show up as slower growth, reduced egg production, or general lack of condition.
When To Start and What Size To Use
Chicks can start receiving grit as early as their first week, especially once they’re eating anything beyond starter crumble. The key is matching the grit size to the bird’s age. The American Pastured Poultry Producers Association breaks it into three stages:
- Starter size: weeks 1 through 3
- Grower size: weeks 4 through 7
- Developer/layer size: week 7 and beyond
The general rule is to offer the largest size your birds will eat in normal quantities. If they’re consuming too much grit, that’s a sign to move up to the next larger particle size, which they’ll eat less of.
How To Offer Grit
The simplest approach is free-choice feeding: put insoluble grit in a separate container and let your chickens take what they need. Chickens are good at self-regulating their grit intake when it’s always available. A small dish, a wall-mounted hopper, or even a pile on the ground in a dry spot all work fine. Keep it separate from their main feed so they can choose when and how much to consume.
If you’re also supplementing with oyster shell for laying hens, offer that in its own separate container rather than mixing the two types together. This lets non-laying birds (and roosters) avoid the extra calcium while laying hens take what they need. Chickens with a calcium deficit will actively seek out the oyster shell on their own.
Free-range flocks with access to varied ground, gravel paths, or rocky soil will often find enough insoluble grit naturally. But if your birds range on soft grass, sand, or mulch without much stone, supplementing is still a good idea. Soluble grit for calcium should be offered to laying hens regardless of whether they free-range, since natural foraging rarely provides enough calcium to keep up with daily egg production.