How long for calcium deposits to improve, or other reasons for brittle shells?

[Agathe]

I've recently merged chicks (now laying) with my older hens. Because I've had two flocks I've also ended up with surplus grower feed. In order not to waste this I have mixed layer feed with grower feed. They do have access to oyster shells aside from this. In addition I live on an island so there is access to shells in the soil. All chickens have continued laying as normal except for one chicken who now produces eggs with very brittle shells. First time it happened I couldn't be sure if it wasn't any of the new chickens with a malfunction, but once this happened more than once I got them back on only layer feed again. However, a week or two has passed and she still lays brittle eggs. How long does it take to replenish calcium deposits? Or could there be other reasons this happens? The chicken I suspect is low on the pecking order (though not the lowest) and might just not eat as much as the others. She's also the least bright chicken of the bunch and might not even eat any of the oyster shells. There are 3 feeders for 9 chickens and there is always room at the feeders, so that shouldn't be a problem. How can I help and is there a way to still feed them the layer feed without running into this issue again? The older chickens are a year and a half, the newer just started laying, so age is not an issue. No other apparent health issues. I've started saving egg shells to feed back to them but also might not the rest of the chickens end up with too much calcium?

 

[aart]

The older chickens are a year and a half, the newer just started laying, so age is not an issue.

Actually that could be the issue.
If you live in the northern hemisphere those 18mo birds are getting ready to shut down egg production and molt. You can get some funky eggs around molting time.

 

[Agathe]

Actually that could be the issue.
If you live in the northern hemisphere those 18mo birds are getting ready to shut down egg production and molt. You can get some funky eggs around molting time.

Oh, right, I had no idea! I was wondering because I know some never feed layer feed and still are okay, so I was figuring I should be able to feed them a mix.

 

[aart]

I was wondering because I know some never feed layer feed and still are okay, so I was figuring I should be able to feed them a mix.

Feeding a mix may or may not be effective.
I have only fed a 20% all flock type feed and provide oyster shell in a separate feeder for the active layers.

 

[Shadrach]

I've recently merged chicks (now laying) with my older hens. Because I've had two flocks I've also ended up with surplus grower feed. In order not to waste this I have mixed layer feed with grower feed. They do have access to oyster shells aside from this. In addition I live on an island so there is access to shells in the soil. All chickens have continued laying as normal except for one chicken who now produces eggs with very brittle shells. First time it happened I couldn't be sure if it wasn't any of the new chickens with a malfunction, but once this happened more than once I got them back on only layer feed again. However, a week or two has passed and she still lays brittle eggs. How long does it take to replenish calcium deposits? Or could there be other reasons this happens? The chicken I suspect is low on the pecking order (though not the lowest) and might just not eat as much as the others. She's also the least bright chicken of the bunch and might not even eat any of the oyster shells. There are 3 feeders for 9 chickens and there is always room at the feeders, so that shouldn't be a problem. How can I help and is there a way to still feed them the layer feed without running into this issue again? The older chickens are a year and a half, the newer just started laying, so age is not an issue. No other apparent health issues. I've started saving egg shells to feed back to them but also might not the rest of the chickens end up with too much calcium?

If the other hens are laying eggs with sufficiently strong shells then this suggests that overall the diet is fine.
Rather than messing about with the feeds, deal with the one hen and her diet.
You could provide the hen producing thin shelled eggs a calcium supplement.
Calcium Citrate would be ideal if you can get it. Calcium Carbonate will do but isn't as quicky absorbed.