Grit vs Oyster Shell for Chickens
These are not interchangeable and one cannot do the other's job. What each is for, who needs it, and how to offer both.
The short version
These are two different products for two different jobs and swapping them causes real problems. Grit is insoluble crushed granite that sits in the gizzard and grinds food, and any bird eating anything other than commercial crumble or pellets needs access to it. Oyster shell is soluble calcium carbonate that dissolves and supplies calcium for egg shells, and it is for laying hens only. Offering oyster shell to chicks, cockerels or non laying birds risks kidney damage from excess calcium. Offer both free choice in separate containers and let the birds take what they need.
At a glance
| Manna Pro Poultry Grit, Insoluble Crushed Granite | Manna Pro Crushed Oyster Shell | |
|---|---|---|
| What it does | Grinds food in the gizzard | Supplies calcium for shells |
| Dissolves | No | Yes |
| Needed by chicks | Yes if eating anything but crumble | No |
| Needed by cockerels | Yes | No |
| Needed by laying hens | Yes | Yes, free choice |
| How to offer | Separate free choice container | Separate free choice container |
Choose the Manna Pro Poultry Grit, Insoluble Crushed Granite if…
Provide grit to any bird with access to grass, treats, scratch or kitchen scraps, and to chicks eating anything beyond starter crumble. Birds with free range on gravelly ground often find their own, but do not assume it, and a bird on soft soil or in a bedded run will not. Use chick sized grit for chicks and standard for adults. Offer it in its own small container rather than mixing it into feed, so birds take what they need.
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Choose the Manna Pro Crushed Oyster Shell if…
Provide oyster shell free choice to laying hens, in a separate container from the grit and separate from the feed. Hens regulate their own calcium intake surprisingly well when it is offered this way. Do not mix it into feed that non layers and cockerels also eat. Thin, soft or shell less eggs are the usual sign of a calcium shortfall, though they also occur in very young pullets, in old hens and with certain infections, so persistent problems are worth a vet's opinion.
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Related
Comparison based on published manufacturer specifications and the general consensus of owner reports. We have not tested these products side by side. Confirm current specifications and prices before buying. As an Amazon Associate we earn from qualifying purchases, at no extra cost to you.
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Frequently Asked Questions
Can I feed crushed eggshells instead of oyster shell?
You can, and it recycles something you already have. Dry the shells thoroughly and crush them, ideally beyond recognition so birds do not connect them with the eggs in the nest box. The practical drawback is consistency: oyster shell comes in a large particle that stays in the gizzard overnight, releasing calcium when the shell is being formed, and finely crushed eggshell passes through faster. Many keepers offer both.
Does layer feed contain enough calcium already?
A complete layer feed is formulated to meet the requirement for an average hen, and many flocks do fine on it alone. Free choice oyster shell alongside covers the individual variation, since a heavy layer needs more than an average one and an older hen absorbs it less efficiently. It costs very little and the birds only take what they want.
My hens are laying soft or shell less eggs. What does that mean?
Occasional soft eggs from a pullet just coming into lay, or from a hen in a heatwave, are common and usually resolve. Persistent soft, thin or shell less eggs point at a calcium or vitamin D problem, at heat stress, at age, or at an infectious cause such as infectious bronchitis, which permanently affects shell quality in some birds. If it continues across several hens, talk to a poultry vet rather than adding more supplements.
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