Jenny,
Our Australorps lay hard-shelled eggs, too. We don't supplement their diet with calcium, just give them layer feed. I think that if the hens are fed well, the egg shells are harder than the store-bought kind. If the shells remain hard, you won't have to give them any supplement like oyster shells.

There are four nutrients that control calcium levels and its use by the body in most living animals/birds.

Vitamin D and K tell the body to absorb calcium and maintain good calcium blood levels (to put it simply) and Boron and Magnesium tell the body what to do with it. Of the four, vitamin D and Boron are usually the ones needed.

Sometimes there is a lot of calcium in their drinking water if from a well/city system. Some save rain water for their birds; it is ph natural and for the most part pure.

Adding boron 6mgs per gallon in their drinking water (only source) 2-3 times a week will prevent buildup of calcium where it shouldn't be (dissolve in 8 oz of distilled hot water 140F to 180F after its fully dissolved, dilute to 1 gallon with distilled water). Too much calcium being pulled from the bloodstream to form a super hard/thick shell can shorten the production life of your hens.

If the shell is smooth and has no rough areas they are probably normal shells-you will notice a difference between store bought and home grown egg shell in a big way. Being hard to break doesnÂt necessarily mean too much calcium being used to make the shell. The above boron supplement will not hurt normal shell production in any bird. It will; in fact; lower the cholesterol levels in their eggs/meat making them healthier to eat.

Seramas, where would I buy Boron?

Cheapest and best quality is from Puritan's Pride Item #005820 3mg tablets-100 to a bottle--2 for $4.49 or 5 for $8.98. PuritanÂs Pride is cheaper than the cost of one bottle of the same quality anywhere else. It has a very long shelf life so don't be afraid to buy the 5 bottle offer.

Here is a link that might be useful: Boron

Our chickens had very hard shells for about the first year or two. People complained! They laughed but they griped. In the meantime the shells have become less hard. The eggs are still awesome - big dark yellow yolks and great taste. I just figured it was part of growing up for the girls.

I used to have an egg business, but just keep them for family now. My eggs were/are awesome. Big, fresh, rich, and hard-shelled. I have found customers will find something to fault. Be it the hard shells, or that fresh ones don't peel easily. I have even had them ask about the yolks standing up when they're cracked. I usually just counter with "you're not used to buying fresh, home raised eggs, are you?"