A laying hen uses a lot of calcium to make eggshells. If she doesn’t get enough, eggs can become thin or soft, and her body may draw calcium from her bones. Oyster shell is a simple way to offer extra calcium. Manna Pro Oyster Shell is one of the most common brands. This review explains how and when to use it.
Bottom Line: Manna Pro Oyster Shell is an affordable, widely available calcium supplement for laying hens. It works best offered free-choice in a separate dish, so each hen can take what she needs. It shouldn’t be mixed into feed for chicks, young pullets or flocks with many non-laying birds.
At a Glance
| Feature | Details |
|---|---|
| Type | Crushed oyster shell calcium supplement |
| Use | Free-choice in a separate dish |
| Best for | Laying hens |
| Not for | Chicks and young pullets |
| Sizes | Various bag sizes |
What It Is and How It Works
Oyster shell is a slow-release source of calcium. Hens eat it as needed, and it dissolves gradually in the digestive system.
Even hens on layer feed may benefit. Calcium needs vary with age, breed and laying rate. Older hens and heavy layers often need more.
Thin or soft shells can also be caused by other problems, including illness and stress. See egg binding in hens and signs of a sick chicken.
Strengths
- Affordable
- Widely available
- Easy to offer free-choice
- Helps support strong eggshells
- Hens self-regulate intake
Limitations
- Not suitable for chicks
- Can be wasted if mixed into feed
- Some hens ignore it
- Doesn’t fix shell problems caused by illness
How to Offer Oyster Shell
- Place it in a separate dish or feeder.
- Keep it available at all times for laying hens.
- Don’t mix it into feed for mixed flocks.
- Refill as needed.
Some owners also feed back crushed, baked eggshells. Bake them to reduce disease risk and crush them so they don’t look like whole eggs, which can encourage egg eating.
Before You Buy
- Offer in a separate dish.
- Keep it away from chicks.
- Watch eggshell quality.
- Check layer feed calcium levels.
- Ask your vet about persistent shell problems.
Who It Suits
| Good fit if… | Consider something else if… |
|---|---|
| You have laying hens | Your flock is mostly chicks or non-layers |
| You want an easy calcium source |
Alternatives to Consider
| Option | How it differs |
|---|---|
| Crushed baked eggshells | Free calcium source |
| Layer feed alone | May be enough for some hens |
| Calcium supplements | Vet-recommended for specific needs |
When to Call Your Vet
Contact your vet if:
- Hens lay soft-shelled eggs often
- A hen strains to lay
- A hen seems weak or lethargic
Frequently Asked Questions
Do hens need oyster shell if they already eat layer feed?
Layer feed contains calcium, but needs vary between hens. Many owners offer oyster shell free-choice so heavy layers and older hens can top up.
Can chicks eat oyster shell?
No. Chicks and growing pullets don’t need extra calcium, and too much can harm their kidneys. Keep oyster shell where only laying hens can reach it, if possible.
Should I mix oyster shell into the feed?
It’s better to offer it in a separate dish. Mixing it in forces every bird to eat it, including those that don’t need it.
Why aren’t my hens eating the oyster shell?
They may already be getting enough calcium from their feed. Hens tend to eat more when they’re laying heavily.
Can roosters eat oyster shell?
Roosters usually ignore it when it’s offered separately. Problems are more likely when oyster shell is mixed into feed for a mixed flock.
Can I feed eggshells instead of oyster shell?
Yes. Bake eggshells to reduce disease risk and crush them finely so hens don’t link them with whole eggs.
How much oyster shell does a hen eat?
It varies with diet, age and laying rate. Refill the dish as needed and watch how quickly it goes down.
Will oyster shell fix soft-shelled eggs?
It can help if a lack of calcium is the cause. Soft shells can also come from young hens starting to lay, stress, heat or illness, so persistent problems are worth a vet visit.
What size oyster shell should I buy?
Most brands sell a crushed size made for adult laying hens. Very fine powder is harder for hens to pick up and can be wasted.
Do hens need grit as well as oyster shell?
Yes, if they eat anything besides complete feed. Grit helps grind food in the gizzard, while oyster shell provides calcium. They do different jobs.
Pet Health Man is independent and isn’t paid by the brands we review. Product formulas, specifications and prices change, so check the current label or the manufacturer’s information before you buy.
This article is for general information only and isn’t a substitute for professional veterinary advice. If you’re worried about your pet’s health, contact your veterinarian or an emergency animal hospital.
