Oyster Shells, Eggshells, And Chickens The Complete Guide

Do you know that an eggshell consists of almost pure calcium? Yup, this is why it’s critical to replenish our chickens’ calcium reserve to ensure that they are well protected from severe health conditions. Fortunately, eggshells and oyster shells are cost-effective and proactive methods to ensure our hens stay strong and healthy while producing nutritious, hard-shell eggs.

Most laying hens will benefit from a calcium supplement. For a cost-effective option, feed the chickens dried and crushed eggshells or consider ground-up oyster shells as they are full of calcium carbonate. Ensure that you keep them separate from their regular food to prevent overfeeding and harming the hens.

Luckily, we can easily prevent soft-shell eggs and critical health conditions by feeding our hens oyster shells and eggshells. Let’s discuss which option is best and how to feed them to your ladies to keep them and their eggs strong and healthy.

Photo 165778066 © Natallia Khlapushyna | Dreamstime.com

Do Chickens Benefit From Oyster Shells And Eggshells?

The natural process of forming and laying an egg tends to deplete the hen of its calcium reserves. Without recharging these supplies, your chickens may not lay as many eggs, or can lay soft-shell eggs, become egg-bound, or even worse − potentially having the egg stuck and breaking inside of her body.

The truth is, the hens aren’t the only ones affected by the lack of calcium. You are affected directly as the eggshells primarily protect the egg from dangerous diseases by preventing harmful bacteria from sneaking inside. 

So, to prevent you from worrying about harmful pathogens residing in your breakfast or selling sickly eggs to local customers, do yourself and your hens a favor by giving them free access to crushed oyster shells and eggshells. 

Here’s some more information on chicken food poisoning and feed safety.

Calcium Supplements For Chickens

A solid and hard eggshell is more likely to withstand outside pressure, while the soft, weak egg shells break easily.

While most chicken feeding companies state that chicken feed should provide adequate calcium for your hens, every chicken has different dietary requirements. Freely offering a calcium supplement will allow the hens who need a boost to access the additional calcium easily. 

Calcium will ensure that the chickens have healthy, thick, and unbreakable eggshells (well, not completely unbreakable, but you understand what I mean).

Eggshells mainly consist of calcium carbonate and are fortunately a free supplement on hand if you’ve got hens laying eggs already. Oyster shells, also called soluble grit, are another fantastic supplement to a laying hen’s diet as they are a high calcium source. 

Find out more about why your chickens need to eat grit.

Oyster Shells For Chickens

Due to an egg containing between 94 and 97 percent calcium carbonate, all of which is absorbed directly from the chicken’s body, a calcium supplement can be beneficial for your laying hens.

As the name suggests, oyster shells are the ground-up shells of oysters. However, in some cases, they may contain traces of other shells.

Oyster shells are high in calcium, making them a perfect supplement for chickens who aren’t receiving adequate calcium from their layer feed. 

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Do All Chickens Need Oyster Shells?

While many of your chickens will significantly benefit from eating oyster shells, not all will need the additional calcium supplement. For example, if your hens aren’t laying eggs yet, their feed should contain enough calcium, and they typically won’t need oyster shells.

Likewise, some chicken breeds naturally have a higher need for calcium than others, and the diet of a laying hen differs from a juvenile hen − a laying hen’s diet will require higher doses of calcium to produce hard-shell eggs.

That said, different chicken breeds also lay at different paces; some hens lay an egg almost every day (every 26 hours), while others only lay eggs every third or fourth day. So, your hens laying eggs once per day may need more calcium supplementation than those laying once or twice a week.

It’s best to supply oyster shells to your hens individually so that only the chickens who need the supplements can access them.

As a tip, look out for these signs of calcium deficiency in hens:

  1. Soft-shell eggs 
  2. Eggs with thin shells
  3. Eggs without a shell
  4. Broken eggs
  5. Slow egg production

There are other dietary issues that may affect your chickens, here’s what to do if your chickens are too skinny.

How Do Chickens Benefit From Oyster Shells?

Like other egg-producing species, a diet strongly impacts egg production. However, chicken hens are susceptible to nutritional deficits compared to other species.

For your hens to have strong eggshells, they need access to plenty of calcium. So, we mainly want to give oyster shells to our laying hens to benefit them in the following way:

  • Due to eggs consisting of around 95 percent calcium, the additional calcium found in oyster shells will encourage solid and hard-shell eggs that reduce the risk of eggs breaking.
  • The hard shells from the calcium supplementation will reduce the risk of bacteria and harmful pathogens entering the egg.
  • Extra calcium in oyster shells will help the hens stay strong and healthy by reducing the risk of bone damage, as laying eggs can lead to weak and brittle bones in laying hens.
  • The calcium found in oyster shells will strengthen the chickens’ blood vessels.
  • Oyster shells will aid in protecting and strengthening the chicken’s immune system while improving its cardiovascular functioning.
  • Oyster shells help encourage continued egg production.

Check out my latest article on what to feed free range chickens to ensure your hens get a balanced diet.

How Often Should You Feed Chickens Oyster Shells?

You’ll want to leave a separate bowl or detached feeder with crushed oyster shells to allow your hens to access it freely when needed.

Although you can sprinkle the oyster shells into the feeder, you risk forcing your chickens to consume excess calcium when they do not need it; this can lead to dangerous health conditions.

So, instead of mixing oyster shells with your chicken feed, allow the chickens to self-regulate how much calcium they need by keeping it separate alongside the chicken feed. Generally, your hens will know how much and when they need the calcium supplement. 

Then, refill the bowl once the chickens finish the oyster shells. In addition, try to provide the oyster shells year-round even if your hens are molting or broody; it will help to strengthen the hens’ bones and encourage solid and hard-shell eggs later in the season.

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Should You Feed Oyster Shell To Chickens That Aren’t Laying?

While it won’t hurt to separately feed oyster shells to chickens that aren’t laying eggs, you generally won’t need to worry about giving the additional supplement; their feed should contain enough calcium to keep them healthy.

You do not have to feed oyster shells to the following chickens:

  • Chicks
  • Juveniles or pullets that have not yet started laying 
  • Older hens that aren’t laying anymore
  • Roosters

So, if you’re raising a mixed flock of chickens, keep the oyster shells separate from the feeder so that the birds who need the supplement can access it; this will prevent overfeeding your chickens’ calcium which can be detrimental to their health.

Not sure what to do with your hens who no longer lay? Check out my article, Can You Eat An Egg Laying Chicken?

Chickens typically only consume as much calcium as they need, but when you mix it with their feed, they have no control of the amount they absorb.

Side effects of too much calcium include:

  • Kidney failure
  • Metabolic issues
  • Egg binding
  • Leg abnormalities

Here’s how often you should collect your chicken eggs.

Eggshells For Chickens

Feeding your chickens eggshells may sound like downright cannibalism, it certainly is not. Chickens are known to consume their eggshells out in nature. 

More so, chicken eggs are freely available if you have mature hens laying eggs at home, and it seems to be what they prefer compared to oyster shells. Also, why not put the “waste product” to good use?

While crushed and flaked oyster shells are specifically available for feeding your chickens extra calcium, many of the fussy hens find oyster shells unappetizing and refuse to touch them. In comparison, the girls gobble down the crushed eggshells in no time!

Choosing eggshells or oyster shells to supplement your laying hens is a personal choice, but your flock may decide for you at the end of the day. However, if you sell your eggs, you may not have enough leftovers to spare for your chicken flock, making oyster shells the second-best alternative. 

When To Provide Eggshells To Chickens

There are a few critical factors to consider before feeding all your chickens eggshells.

First, their age. Chickens do not need additional calcium until they come into lay or are nearly ready to (around 18 weeks old). Prematurely feeding your flock calcium can harm your younglings and cause kidney damage and other health conditions. 

You can put out the eggshells once one of the chickens (assuming they are the same age) starts laying.

Then, it would be best to let your chickens decide if they want the calcium supplement, they tend to know what their body lacks and needs. So, avoid mixing the crushed eggs into their feed as a hidden nutritious treat as it can lead to an overdose of calcium.

Instead, keep the crushed eggshells in a separate bowl allowing the hens to access additional calcium freely without forcing them to consume it.

The time of day that you feed chickens is also important, Here are some details on feeding your chickens at night.

Benefits Of Feeding Chickens Eggshells

Laying eggs requires large amounts of calcium to ensure the egg has a protective shell and healthy membrane.

Proving eggshells to your hens that lay eggs prevent low-quality eggs that easily crack and break; it also offers healthy nutrients like magnesium, potassium, sodium, and phosphorus.

Can You Give Chickens Store-Bought Eggs?

Sourcing appropriate eggshells is a critical aspect before providing them to your hens. 

It is best to avoid using store-bought eggs and eggs from other farms as these eggs can potentially carry harmful bacteria that can make your flock sick.

So, for the safest option, only use the eggs from your flock; this will reduce your waste while repurposing them as a bonus calcium source for your hens.

How To Prepare Eggshells For Your Chickens?

Egg-eating is, unfortunately, a difficult habit to break once your chickens start eating their eggs. So, drying your eggshells in the oven will reduce the odor and taste of fresh shells, reducing the likelihood of your chickens associating them with the fresh eggs they lay − and developing a taste for them. 

So, as tempting as it seems to toss large pieces of cracked eggs shells to your hens after frying up an egg, we prefer to take precautions and follow a few other straightforward steps.

  • First, save up the eggshells in a container as you use eggs and store them in the fridge to prevent bacterial growth.
  • Next, spread the shells onto a baking pan or cookie sheet to ease the cleaning process afterward.
  • Now, bake the eggshells in the oven at 300°F for several minutes (around five to ten minutes should suffice) to ensure that all the harmful bacteria die from the heat; this step is critical if the eggs aren’t freshly laid. More so, drying the eggshells in the oven makes it simpler and faster to crush.
  • Allow the eggs shells to cool.
  • Next, throw the shells into a zip-lock bag to crush the eggshells into a fine powder with a rolling pin. You can also try using a food processor or coffee grinder to grind the eggshells.
  • Finally, store the crushed eggs shells in jars in the refrigerator and replenish their outside bowls as needed.

Alternatively, if you are short of time and do not feel like going through the hassle of drying and grinding eggshells, or if you sold or gave your eggs away, you can purchase pre-dried, crushed, or ground eggs at the store. 


It’s incredible to think that a small act of feeding your hens oyster shells or eggshells can play such a significant role in their health and egg production.

Always try to ensure that your ladies have free access to either of the two calcium sources, and be sure to keep it in a separate bowl to prevent health conditions from occurring from too much calcium.

Dane McManis

Dane started learning about farming while volunteering on a farm. Now he and his wife raise chickens, pigs, and ducks on their small farm with their two little girls.

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