You can also give them other sources of calcium when they're laying. We went with some oyster shell because we'd just got them and didn't have a good supply of egg shell laid in. I've been saving them since however and when the oyster shell is gone, I'll just crush the shells and feed them back to the girls. All dark green leafy vegetables are also high in calcium...spinach, kale, chard. Milk products as well...both for protein and calcium...I make yogurt and give them some once or twice a week, and they're crazy about any kind of cheese. Cooked (to remove the toxins) dried beans are good for both protein and calcium. You want to keep an eye on egg production though...if they're not laying they don't need that much calcium...most of it goes to the production of the shell.