Why Use Crushed Oyster Shells for Chickens (Benefits)

Nothing is more disappointing than expecting beautiful and healthy eggs from our coop only to find fragile and oddly shaped eggs. 

If this has happened to you, you’ve undoubtedly wondered what in the world could cause such poor quality eggs. 

The answer is calcium deficiency. 

Oyster shells make an excellent and affordable source of calcium and grit for chickens. 

Both calcium and grit are vital for digestion and egg-laying. 

While most feeds provide calcium, it’s sometimes not enough to fulfill the needs of our laying hens. 

Crushed oyster shells provide calcium and grit for chickens. Calcium helps with egg-laying, and deficiencies in this mineral often result in fragile and oddly shaped eggs. Chickens also require grit to properly digest food, and crushed oyster shells provide this. 

Most well-seasoned chicken keepers incorporate crushed oyster shells into their daily regimen for their backyard flock. 

Find out why crushed oyster shells are so crucial for our chickens’ overall health and egg quality. 

crushed oyster shells for chickens

What Are The Benefits Of Using Crushed Oyster Shells For Chickens?

Chances are you’ve noticed the bags of crushed oyster shells at your local feed and seed or farm store. 

What exactly is it used for? 

While crushed oyster shells may provide other services, their main purpose is to incorporate calcium and grit for egg-laying hens. 

Most chicken feed products provide calcium in their nutritional profile. 

However, many chickens require additional calcium. 

Luckily, crushed oyster shells are an affordable and easily accessible source of calcium for chicken keepers to give to their flock. 

Calcium is essential in the egg-laying process. 

Laying hens are on a 24-hour egg production cycle. 

This means they use a lot of calcium every day to produce eggs. 

If they experience a calcium deficiency, their eggs often become misshapen or fragile. 

You may find the eggshells break when you go to pick them up. 

If this happens, it’s a sure sign your hens would benefit from an increase in their uptake of calcium. 

Another amazing benefit of using crushed oyster shells for chickens is the grit provided by the ground-up shells. 

Chickens need grit to digest food properly. 

They do not have teeth to chew up food as humans do. 

Instead, they break food down in the gizzard. 

Chickens will often forage around for sand, dirt, and small stones. 

These materials go to the gizzard, where the chicken’s digestive system uses them to further grind up the food to make it more easily digestible. 

Why Do Chickens Need Oyster Shells?

Crushed oyster shells are a staple for backyard chickens. 

The extra calcium source and soluble grit in the crushed oyster shell are key for keeping your chickens happy and healthy. 

Most of us keep chickens for their prolific egg production. 

Shouldn’t we want the highest quality eggs possible if this is the case? 

The crushed oyster shells are a great way to increase overall egg quality. 

It is also extremely beneficial for promoting proper digestion by providing grit. 

We also want our chickens to be happy and healthy, and a properly functioning digestive system will help keep them from suffering from adverse health conditions. 

What Does Calcium Do For Egg Laying Hens?

The calcium boost from oyster shells is significant for egg-laying hens. 

Hens need a lot of calcium to produce strong eggshells. 

Since each laying hen lays an egg every day on average, it’s essential to ensure they have access to the additional calcium that crushed shells provide. 

If your laying hens suffer from calcium deficiency, their eggs will show signs. 

This often means fragile eggshells, oddly shaped eggs, and sometimes even rubber eggs. 

Rubber eggs look exactly how they sound. 

They have rubbery shells and do not look very appetizing at all. 

Lack of calcium also leads to other health problems. 

If your chicken is not forming eggs properly, the eggs may break in the vent and cause infection or injury. 

They also may feel depleted. 

Calcium deficiency is also linked to a weakened immune system. 

This means your chickens will be more susceptible to diseases and infections. 

Making sure backyard flock gets adequate calcium per day is essential for their overall health and egg production. 

Benefit Of Grit From Oyster Shells For Chicken Digestion

The digestive tract of chickens is very different from ours. 

For starters, they do not have teeth to break down food. 

Because of this, they need a bit of help to break down food into small enough pieces for digestion. 

This is done in the gizzard. 

The gizzard is the organ responsible for milling down bits of food by using grit. 

Chickens gather grit by foraging for sand, pebbles, and small stones. 

The gizzard then uses these materials to grind down food to make it easier to digest. 

Crushed shells provide an excellent source of grit for the gizzard. 

Spreading the powdery crushed shells in the chicken coop provides an excellent source of grit for digestion. 

Since all chickens need grit to properly digest food, it’s crucial to provide an accessible option for your flock. 

Seeing as the crushed shells of oysters also provide additional calcium, it provides multiple benefits in addition to grit for digestion. 

Signs Your Backyard Chickens Need Oyster Shells

how to tell chickens are calcium deficient

Overall, recommend incorporating crushed oyster shells into your chicken’s daily feed. 

The benefits speak for themselves. 

Also, they are easily accessible and inexpensive. 

While you shouldn’t force your backyard chickens to eat oyster shells, spreading them in the coop for easy access is beneficial. 

There are also times when your backyard flock will show obvious signs. 

Most of these are indicators of calcium deficiency. 

Many oyster shell products incorporate calcium from oyster shells and coral calcium. 

This makes them an excellent source of valuable minerals and an easy way to get more calcium in hens. 

Keep an eye out for these signs of calcium deficiency in your backyard chickens to see if they need crushed oyster shells. 

Weak Eggshells

Laying hens will lay eggs with weak shells when they are deficient in calcium. 

If the eggs break during the laying process or collection, it’s time to increase calcium intake for your flock. 

Broken Eggs

If you often find broken eggs in the coop, your chickens may need more calcium from oyster shells. 

Eggshells are high in calcium and need adequate calcium to form properly. 

If the shells are broken, your chicken likely doesn’t have enough calcium to produce strong eggshells. 

Stop In Laying

After a prolonged period of calcium deficiency, your egg-laying chickens may stop laying altogether. 

If your flock has stopped laying, they are showing signs of needing more calcium, and crushed shells will help immensely to fix this. 

Weakened Immune System

There are quite a few causes of a weakened immune system for chickens. 

However, if your chickens show other signs on this list, the cause may be a lack of calcium. 

If your chickens are getting sick or suffering from infections, the calcium in oyster shell powder may help to improve their condition. 

Rubbery Eggs

It is quite surprising to find a rubbery egg for the first time. 

A rubbery egg occurs when the eggshell does not form correctly. 

The result is a squishy egg with a rubber-like shell. 

These often occur in chickens who need additional calcium, which is easily addressed by incorporating crushed oyster shells into their diet. 

Check out our list of every egg issue and what it means for chickens.

How To Give Crushed Oyster Shells To Chickens

Chickens instinctively seek out sources of grit for digestion. 

Because of this, there are many ways to give crushed oyster shells to your flock. 

Whichever way you choose, you’ll be doing a great service to your flock of birds. 

One of the most important things to consider is purchasing a quality product. 

Make sure to buy a reputable brand. Many chicken keepers make their crushed oyster shells as well. 

Whichever way you choose, incorporating oyster shells into your flock’s diet is sure to make each chicken happy. 

Place Oyster Shells In A Separate Dish

This is our most highly recommended way of supplying crushed oyster shells for your chickens. 

While the risk is relatively low, excessive calcium levels are possible. 

As chicken owners, we want to ensure we aren’t putting our flock at risk. 

To avoid this, put the oyster eggs in a separate container for chickens. 

This way, your flock may pick and choose when they wish to eat the oyster shells and prevent them from indulging in too much at a time. 

Mix Crushed Shells Into Layer Feed

Other chicken owners will mix crushed shells into their layer feed. 

Most people recommend keeping crushed shells separate from regular feed to keep chickens from overindulging. 

Still, keeping an eye on the ratio will reduce the risk of anything bad happening. 

Mixing the crushed shells into the regular chicken food will help guarantee an increase of calcium and grit. 

This may also be the best option if your chickens aren’t touching the oyster shell when it is on its own. 

Make Your Crushed Oyster Shells At Home

If you have access to many oyster shells, consider taking the do-it-yourself route by making crushed oyster shells at home. 

Some people harvest oysters and have many leftover shells. 

Others work at restaurants where many oyster shells are thrown away. 

Whichever way you get your shells, it’s crucial to thoroughly clean and scrape the shells out. 

Once they are cleaned, you’ll need to bake them for about 10 minutes at 250° degrees Fahrenheit (121° C). 

This helps to kill any potential bacteria on the shells. 

Once you pull them out of the oven, they will be significantly more fragile and easier to break. 

Using a mallet should be sufficient to fully crush the oyster shells to make your source of calcium and chicken grit. 

Then spread the ground oyster shells in the coop for your flock. 

Spread Oyster Shells In The Chicken Coop

Another easy way to provide crushed oyster shells to your backyard flock is by spreading them on the ground in the chicken coop or run. 

If you’ve ever watched your chickens, you’ve undoubtedly noticed how incessantly they scratch and peck at the ground. 

While they are hoping for a grub or worm, they will also eat up dirt and small stones. 

By spreading the shells in the chicken run, your flock of birds will get all the benefits of the shells. 

The grit with calcium will have your hens producing beautiful eggs quickly. 

Alternatives To Crushed Oyster Shells 

If, for whatever reason, you do not have access to oyster shells or don’t want to use commercial oyster shells, there are other options. 

These alternatives will help incorporate a consistent calcium supply for your flock. 

Some of these options are likely already present on your property or homestead.

Be sure to also check out our exhaustive guide of what foods chickens eat.


Crushed and cooked eggshells from your chickens are a great source of calcium. 

While they do not have as much calcium per gram compared to oyster shells, they still provide extra calcium to your daily chicken diet. 

Some chicken owners refrain from giving eggshells to their chickens. 

This is because they do not want to encourage bad behavior. 

Some chickens develop a taste for eggshells and start to eat their eggs. 

High Calcium Feed

Another way to have happy chickens with adequate calcium and grit is high calcium feed. 

Switching to a different feed with more calcium is an excellent alternative to oyster shells. 

This way, your flock of birds gets more calcium with their meals. 

However, the high calcium feed will not provide the same grit for your birds as the crushed shells. 

Calcium Supplements

Supplements are another excellent alternative for adding extra calcium content to your chickens’ diet.

While they satisfy the calcium needs of your birds, they do not provide grit to aid in digestion. 


There are many food items in our homes and gardens with high calcium levels. 

Keeping table scraps for your chickens will keep them very happy and give them access to calcium. 

Make sure to hold onto these chicken-safe vegetables and other foods to throw in the coop to provide lots of calcium:

  • Swiss Chard
  • Broccoli
  • Rhubarb
  • Cabbage
  • Kale
  • Yogurt
  • Cooked Beans

Crushed Limestone

Crushed limestone is another alternative for excess calcium. 

It is often found in commercial feeds and boosts calcium levels. 

Make sure to buy the correct type of limestone. 

Some products contain other minerals which prevent proper absorption of calcium. 

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Growing up amidst the sprawling farms of the South, Wesley developed a profound connection with farm animals from a young age. His childhood experiences instilled in him a deep respect for sustainable and humane farming practices. Today, through Farmpertise.com, Wesley shares his rich knowledge, aiming to inspire and educate others about the joys and intricacies of rural life.

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