Can Chickens Eat Oyster Shells? What You Need to Know

Oyster Shells in The Market

Article Summary

  • Oyster shells, rich in calcium carbonate, can be added to chicken feed to provide supplemental calcium.
  • Only crushed oyster shells should be fed, as whole shells are too large for proper digestion.
  • Oyster shells should be introduced to chickens around 18-20 weeks of age when they reach the laying stage.

Chicken owners often wonder if feeding oyster shells to their flocks is a good idea. Oyster shells offer several benefits for chickens but also come with some downsides. This article will explore everything you need to know about feeding oyster shells to chickens.

What Are Oyster Shells and Why Would You Feed Them to Chickens?

Oyster shells are the hard, outer covering that protected live oysters. They are made of calcium carbonate and provide chickens with supplemental calcium when added to their feed.

Calcium is crucial for chickens’ health. It helps form strong bones and eggshells. Access to enough calcium ensures chickens lay strong, thick-shelled eggs. It also prevents issues like thin shells, soft bones, and osteoporosis.

Since chickens need so much calcium, many owners choose to supplement with oyster shells. They are a natural, affordable calcium source that chickens seem to enjoy.

The Benefits of Feeding Oyster Shells to Chickens

Chickens Eating Feeds

Feeding oyster shells offers chickens several benefits:

Strong Bones and Eggshells

The main reason owners feed oyster shells is the calcium content. Calcium fortifies bones and eggshells. Chickens with ample calcium will lay noticeably thicker, stronger eggs.

Grit for Digestion

Along with calcium, oyster shells provide essential grit. Chickens have no teeth, so they need grit in their gizzards to grind up food. Oyster shells give an abrasive, grinding texture.

Affordable Calcium Source

Purchasing oyster shell supplements is budget-friendly, especially when buying in bulk. The cost per pound is lower than many other calcium supplements on the market.

Readily Available

Since oyster shells are a byproduct of the seafood industry, they are easy to find. Most feed stores stock them in 50-pound bags. You can also sometimes source them locally from restaurants that serve oysters.

Natural Calcium Source

Unlike refined calcium powders, oyster shell is an all-natural supplement. Many owners prefer giving their chickens natural foods when possible.

As part of a well-rounded diet, it’s essential to explore what animal feed chickens can eat beyond supplements like oyster shells. Discovering suitable grains, vegetables, and protein sources can further enhance the nutritional profile of your flock.

Can Chickens Digest Oyster Shells Properly?

Yes, chickens can digest crushed oyster shells without issue. Their gizzards easily grind up and process the shell fragments. The shell pieces help breakdown other feed components in the gizzard as well.

Whole oyster shells, however, should not be fed to chickens. The shells need to be crushed into smaller fragments for chickens to digest them.

Do Chickens Need Oyster Shells?

While chickens can benefit from oyster shells, they are not an essential part of their diet. Chickens’ actual dietary calcium needs can be met through their feed and access to greens.

However, most feed is grain-based, which does not provide optimal calcium. Greens and bugs supply some dietary calcium but not enough for peak egg production. This makes supplemental calcium critical for active, laying hens.

Oyster shell is an affordable, natural calcium supplement. But other options like limestone grit or refined calcium powders can also be used.

Can You Feed Chickens Oyster Shells Raw?

Raw, dried oyster shells are perfectly safe for chickens to consume. In fact, dried oyster shell supplements from feed stores contain raw, unprocessed shells.

Shells must be thoroughly dried first, as raw oyster shells may pose contamination risks…

The key is that the shells must be thoroughly dried first. Raw oyster shells may pose contamination risks if they still contain traces of oyster meat or moisture.

Once dried, the shells are shelf-stable and safe to feed raw. Simply crush them first and offer free-choice in a supplement dish.

Should You Feed Whole or Crushed Oyster Shells?

Only crushed oyster shells should be fed to chickens. Whole oyster shells are too large and hard for chickens to digest properly.

The shells need to be broken down into smaller fragments that chickens can swallow. Their gizzards cannot grind chunks that are too big.

Most commercial oyster shell supplements come pre-crushed into small, chicken-safe pieces. If you source shells locally, be sure to sterilize and then crush them yourself before feeding.

A hammer or rolling pin works well for breaking large shells down into bite-sized fragments. Make sure there are no sharp pieces left over.

What’s the Best Way to Feed Oyster Shells?

Here are some tips for feeding oyster shells successfully:

  • Offer free-choice in a supplement dish – Let chickens self-regulate how much they need.
  • Make sure shells are crushed – Do not feed whole shells.
  • Provide grit separately – Offer oyster shell grit in a separate dish from insoluble granite grit.
  • Store in cool, dry area – Heat and moisture can degrade shells over time.
  • Check dish often – Refill as needed so it never stays empty for long.
  • Provide 24/7 access – Calcium needs are ongoing so make shells available at all times.
  • Offer plain shells – Do not mix with feed or other supplements.


Making oyster shell supplements available free-choice in a separate dish is the easiest method. Chickens will eat the amount they need.

Is It Possible for Chickens to Eat Too Much Oyster Shell?

While oyster shell supplements are safe for chickens, it is possible for chickens to overdo it. Consuming extremely high amounts of calcium over long periods can cause kidney damage.

However, calcium toxicity is rare in backyard chickens. When given free-choice access, chickens tend to self-regulate well.

Signs of calcium overdose include decreased appetite, lethargy, and excessive thirst. If you notice these symptoms, remove the oyster shell for a few days to see if they resolve.

As long as chickens are not gorging themselves, the risk of excessive calcium is low. Offering oyster shell supplements according to package directions is unlikely to cause problems.

Can Baby Chicks Eat Oyster Shells?

Young chicks under 16 weeks old should not be fed oyster shell supplements. Their growing bodies cannot yet properly regulate calcium absorption.

Whole Oyster Shells
Whole Oyster Shells

Chick starter feed is formulated to provide balanced nutrition for chicks. Once chicks mature and begin laying at around 16-20 weeks, oyster shell supplements can be introduced.

For the first 4-6 months, baby chicks get all the calcium they need from starter feed. After that, they will benefit from the added dietary calcium boost oyster shells provide.

The Bottom Line: Should You Feed Oyster Shells to Your Chickens?

Oyster shell supplements offer a safe, affordable calcium boost for mature, laying chickens. The shells provide much-needed calcium for eggshell and bone strength.

However, oyster shell is not mandatory for backyard chickens. As long as their overall diet includes ample calcium from other sources, the shells are optional.

Talk to your local feed store to determine if your chicken feed needs supplemental calcium. Free-choice oyster shells are an excellent option for most flocks to support health and maximize egg production.

Just be sure to crush shells properly before feeding. And, as with any treat, feed oyster shells in moderation. Following package directions prevents potential issues with calcium overdose.

Frequently Asked Questions

Do oyster shells have calcium for chickens?

Yes, oyster shells are an excellent source of calcium for chickens. They provide a natural and digestible form of calcium, essential for the development of strong and healthy eggshells in laying hens. Calcium is crucial for overall poultry bone health and helps prevent issues like eggshell abnormalities.

How to feed oyster shells to chickens?

Feeding oyster shells to chickens is simple. Crushed or ground oyster shells can be added to the regular chicken feed. The recommended ratio is approximately 1 to 2 cups of oyster shells per 10 pounds of layer feed. Ensure that the crushed shells are of the right size for the chickens to consume easily. It’s advisable to provide oyster shells free-choice in a separate feeder so that hens can access them as needed.

When to start feeding chickens oyster shells?

Oyster shells should be introduced to chickens when they reach the laying stage, typically around 18-20 weeks of age. At this point, hens require extra calcium to support the production of strong eggshells. Feeding oyster shells before the laying stage is unnecessary and may lead to an imbalance in their diet. Monitor eggshell quality, and if it appears thin or fragile, it’s an indication that it’s time to start supplementing their diet with oyster shells.