Clam shells? There is sure to be some inexpensive source of calcium.
For years ground bone was a cheap source until "mad cow disease" stopped it in most countries.
But as long as your eggs have good hard shells, no soft ones, you should be fine.
For years ground bone was a cheap source until "mad cow disease" stopped it in most countries.
But as long as your eggs have good hard shells, no soft ones, you should be fine.