There are two types of poultry grit available. Flint grit or insoluble grit which is used for grinding down food and Oystershell grit, a source of calcium to help form strong egg shells.

Flint or insoluble grit

Chickens don’t have teeth, apparently, they are very rare, so to grind down their food, they use a strong muscular organ called a gizzard. flint grit for chickensChickens pick up grit whilst foraging, which is kept for a while in the gizzard to perform this grinding process. If your chickens are kept truly free range then they will find enough of this on their own but these days, few of us have the space or the security from predators to be able to allow them to do this naturally.

Flint (or insoluble) grit is cheap and available from most good pet or farm shops, the container you put it in costs a little more though if it is going to last.

Oystershell or soluble grit

oystershell grit for chickensIn order to form strong egg shells, chickens require a certain amount of calcium in their diet. Most of an egg shell is made up of calcium. These days, with the research that has been done for formulated feeds (available as layers mash or layers pellets), it isn’t so critical to provide oystershell grit because layers feeds contain sufficient calcium, however, it’s cheap and it’s easy to mix some in with the flint grit that they need above so it’s a good idea to provide some, in case they need more calcium.

High production hybrid hens are capable of producing a staggering number of eggs in a year on very little feed (known commercially as the ‘conversion ratio’) so they are more likely to need the extra calcium to be able to produce the right number of eggs of sufficient quality.

If you can’t find Oystershell grit from your local store, baked, crushed egg shells will do the same job – after all, they are mainly made up of calcium! Put them in the oven for 10 minutes to dry them out and crunch them up before mixing  them in to your grit hopper.

Although grit is heavy, if all else fails, you can still buy it online here. A small bag lasts for a long time.

Grit hoppers

Grit containers come in a variety of shapes and sizes – the priority is really to make sure it doesn’t get tipped over or filled up with water. There are some good galvanised grit hoppers like this one that will last a lifetime but will cost you a few pounds more to start with.


  1. Love your site and humour. Do many people realise the joke about hen’s teeth “apparently, they are very rare”

    Keep up the good work!


  2. I’m trying to get chickens and this was very helpful, thank you so much for taking the time to make this. I think I have all things sorted and cant wait to get some Golden Comets! I think I will give them a good home. thanks again!

  3. Hello. I just got a few hens and I was wondering if I could make my own oyster grit (you know festivities etc. Got a few shells laying about). Can you tell me if there is a specific “size” the grit should be? (Obviously not too big… But how small is too small?) Is there a method to it? Baking first, or not baking at all? Thank you for your help 😀

    • Hello Lise,
      It isn’t something I’ve done before to be honest, however I would probably bake the shells to dry them out fully (so they don’t go mouldy when stored in a bag) and then break the shell up with a hammer into small pieces. The oyster shell grit that you buy is no more than 4-5mm in size to give you an idea.

      Good luck!

  4. Please stop pedalling the myth of oyster shell grit and the use of it to provide additional calcium too heavy laying birds. Modern layers pellets provide a minimum level of nutrition required to cope with the egg production they are bred to have. The edition of oyster shell grit dilutes the essential minerals and vitamins they require to perform this task. For example an egg is 13% protein layers pellets provides 15% protein and much less if you start diluting search feed with grit. That is only one example of the damage oyster shell grit does to the development of birds in modern times. Birds which are bred to be laying more eggs than ever before.

    • Respectfully, I disagree, but I think you’ve got a point, I think excess calcium intake is caused by layers feeds fed to birds that aren’t laying for long periods of time.

      I don’t believe chickens are eating excess calcium and diluting down essential vitamins and minerals deliberately. I believe the problem is more likely to be because of the calcium that is added to layers feeds that they have to eat in the ration and may not always be laying. They don’t get a choice in taking less of it.

      Like most animals, they will pick and choose what they eat to get the right nutritional balance.

      Ducks are a perfect example of this. When they are laying, they eat more layers pellets. When they stop laying they eat more wheat. Drakes can get sick because of the excess of calcium if they are only fed layers pellets.

      On the other side, by providing additional oyster shell, birds are free to choose it if they need it.
      Chickens will only take oyster shell grit as and when they need it. Mine have it ad-lib and I top it up every now and then, but to be honest, they hardly eat it.

      Whilst eggs don’t contain large amounts of calcium, almost half of an egg shell is made up of calcium so they do need sufficient calcium in their diet that is mostly provided by a complete layers feed (I think we can agree to that).

      -If they need more than their feed is providing (remember free range chickens aren’t just eating layers pellets), they can take some oyster shell.
      -If they have enough in their feed, they won’t take it.
      -And finally (where I think the confusion is): If they are getting too much calcium in a layers ration, they can run into problems like you describe. I do not believe however that it’s caused by oyster shell being provided.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.