How much is too much calcium?

I had two of my egg customers comment on the hardness of the shells of their eggs yesterday, saying that when they went to crack them open for eating they had to give the egg a good whack and it got me wondering.......

My birds have free access to oyster shells and I like to give them a treat, about 3 times a week, of pureed cooked eggs (shells on) with alfalfa meal, flax meal and crushed chilis. Sometime I put a little yogurt into it as well.

Is it possible that they are getting too much calcium and that their eggs can be too hard?

My biggest concern is when I want to hatch those eggs, will the chicks have a problem and what could I be doing to the hens' internal organs, if they're getting too much calcium.

Do you see them eating the free choice calcium? If so, then I strongly doubt that they're overdosing.
On the other hand, it IS possible for a non-laying bird (e.g. roosters and young birds) to get too much calcium.

Hi ipf

I do see them eating the oyster shell occasionally and I am out there a fair bit so I would know if they were hanging around the oyster feeder a lot and they're not. But they do eat some of it for sure.

I was wondering myself before my customers said anything if I should be peeling the eggs (which I'm not willing to do....spoiled chickens) out of concern of O.D.'ing them and then when those customers made the comment I got concerned.

What about the concern of chicks not being able to pip and zip if the shells are quite hard?

I hear you, but I think that chickens (like other animals and even people, if they start young enough) will generally make the right food choices if (and it's a big if) appropriate choices are available. It's possible, I suppose, that the chicks might find pipping difficult, but I would hesitate to try to fix a problem that has not yet occurred. I think you would run a far higer risk of inducing calcium deficiency by withholding oyster shell.

How many eggs per chicken per week do you feed them?

Remember, there has been very strong natural selection for egg shells of just the right thickness. A hen who laid eggs that couldn't hatch would immediately remove herself from the gene pool.

Then there's the Keystone Principle. This being that an arched shape has great resistance to downward or outside thrust. But inward and upward thrust will break an arch.

This translates to an eggshell having more resistance to outward pressure, but giving more easily to the pressure from a chick inside trying to break its way out.

What appears to us as a very hard, dense shell has a different resistance to force from the inside. I have always been more worried about the thick, leather-like membrane inside turkey eggs...how do those poor little turkeys get out of that! So too much calcium might make a hefiter shell, but still, to the chick, his job is easier pushing a curve outward than you pushing a curve inward.

You two are great and I love the knowledge of the members on this forum. Uno, who'd uh thunk? A comment was made on the thick membrane of my EE's egg as well. I love the concept of the Keystone Principle.

ipf, 'how much do I feed' is a good question. I'm not sure but am cutting back, wanting to keep their food intake balanced and not wanting them to get fat. So perhaps, more than they needed in the beginning and less so now. I started this feeding regime when they went into this partial moult as a result of feeding them too low a protein feed over the winter. Anyways, as far as amounts, that's all I can say.

Unless anyone else has different information, I'm satisfied with your inputs.

There's so much to learn about poultry. And I find it all so interesting. Thanks so much to both of you.