What is shell grit and why do your backyard chickens need it?

Updated: 17 February 2023

Chickens don’t have teeth. But they do have a gizzard. A gizzard is an organ found in the digestive tract of chickens that helps them to grind up food. 

All breeds of chickens need access to grit daily; it’s an essential part of their diet and overall health. 

There are two types of grit:

1. Soluble grit - includes shell grit or crushed oyster shell. Both offer a slow-release of calcium, and
2. Insoluble grit - includes tiny rocks and pebbles to aid digestion. 

What is shell grit?

Shell grit is literally tiny whole and broken up seashells. It's a 100% real and natural, and can be found on the shores of lakes and coastlines across Australia.

Shell grit varies in look and texture, depending on where it's sourced. It can be very fine, consistent and almost white, through to coarsely mixed shells. 

Most of the shell grit in Australia that's perfect for poultry comes from the pristine shores of South Australia and is a combination of fine and coarse shell grit, which is graded and sifted by size. 

What size shell grit should I buy for my chickens?

Fine-textured shell grit is more appropriate for small birds like quails.

Medium grade shell grit is perfect for all backyard chicken breeds, including laying hens and pullets - and even ducks!

Coarse-textured shell grit is excellent for geese and Muscovy ducks.

The finer the shell grit, the faster and more easily it is absorbed. However, we want the hen to still access and digest the shell grit after she's retired for the evening to the perch.  

If you’re in Australia, medium-sized shell grit for birds is what you should buy. 

Medium shell grit takes longer to get through the upper digestive tract, which allows for a slower release of calcium around the clock. This means your hen is taking less out of the calcium bone bank when creating an eggshell. 

Why is shell grit necessary for backyard chickens? 

Shell grit for chooks helps them digest food and is an excellent source of slow-release calcium, critical for bone health and strong eggshells. 

When chickens don't get enough calcium from their diet, they draw it from calcium reserves in their bones. 

How much shell grit do I give my chickens?

I'm a big fan of "free-choice feeding". I don't mix shell grit into my chick feed. Instead, I allow them to self-serve and choose when they need supplementing.

The easiest way to offer chickens shell grit is to put it in a small 200ml plastic or ceramic birdcage style feeder, hooked to the side of the chicken house or run. Hang it at the same height as their back so the shell grit won’t get dirty. Changing or refilling smaller amounts frequently works best. I replace or top up their shell grit around twice a week.

Backyard chickens like their shell grit clean and sparking. 

What’s the difference between oyster shell and shell grit for chickens?

Ground-up oyster shell and shell grit are both soluble grits and serve the same function for poultry. Oyster shell grit in Australia is relatively rare and is more common in the US and the UK. In Australia, we tend to find shell grit more accessible. 

Should I give insoluble or hard grit to my backyard chickens?

Fowl that free-range will naturally find and peck at tiny rocks, pebbles and large grains of sand. These are insoluble shell grit for poultry and aid digestion by assisting the grinding of food in the gizzard. 

I know many people who do not offer their hens insoluble grit - including some free-range farms. 

You may be thinking that offering shell grit means you don't have to offer hard grit. However, when I asked two of Australia’s best Old English Game breeders for their thoughts on grit, both were quick to emphasise the importance of insoluble, hard grit. 

Given that these two men have been breeding fowl for over 70 years each and have hardy, disease-resistant flocks, I’ve taken on their advice!

Offering hard grit to your flock is just another "2%" thing we can do to improve their health. 

Do I need to feed shell grit to chicks and growers? 

No. Chicks and growers up to 16 weeks benefit from insoluble grit (coarse sand, rocks and stones, etc.) but not calcium-releasing grit such as shell grit. 

Offering small amounts of whole wheat grains from day 10 can also help activate the digestive tract. Calcium requirements of pullets dramatically increase when they commence laying - they're working hard to put a shell on that egg!

Do I need to feed shell grit to roosters? 

Roosters will still peck at shell grit, but their requirements are far less. I prefer to offer shell grit as "free choice" instead of mixing it into chicken feed; this allows them to supplement as required. 

Why not just feed chickens a calcium supplement?

While the calcium-magnesium balance applies to dogs, cats and livestock; it is calcium and phosphorus that are the important elements to balance in poultry. 

Excess calcium in poultry can inhibit phosphorus, which can lead to kidney damage, soft bones and, according to Damerow (1994), make them susceptible to parasites. 

Slow-release calcium is what your chicken want and need. Stick to a balanced diet supplemented with shell grit or oyster shell. 

Where to buy shell grit in Australia

The best shell grit for sale for your chickens is available on the Chicken Coach online poultry supplies Australia shop and is perfect for laying pullets and hens.

Want your chickens to be the healthiest and happiest they can be? I offer backyard chicken workshops, online programs, phone coaching, and in-person support to families, schools, and free-range egg farmers. Visit my online shop for natural, tried-and-tested poultry supplies in Australia.

Grab my free guide, The First 8 Steps To Naturally Healthy & Happy Backyard Chickens now! 

Elise McNamara, Chicken Consultant & Educator.