I have slightly over a ton of it so no personal experience but if you do not feed the chickens enough calcium they do not lay.
Worse they may become egg bound which is a problem you really do not want to have.
Yes, all that chicken egg production requires supplemental calcium sources.
Most egg 'laying mash' includes calcium from a variety of sources including crushed oyster shell, of which most consumers are totally unaware.
This also represents the interdependence of other sources of vitamins and minerals that are found in our food production, with poultry highly dependent on aquaculture for calcium.
I’ve started researching snails as chicken feed. It’s hard to find enough data to do the kind of analysis I would like, but so far they look promising.
With home-grown chicken food, it’s easy to get too much protein, and hard to get enough calcium. Too much protein can actually cause organ damage in chickens. Snails in the shell *might* have the right balance of the two, when combined with greens and seeds. But like I said, some of the data is hard to find.