Laying hens need calcium to form all that good strong eggshell, almost one shell a day! That’s a lot of calcium! You can give them ground oystershell, it’s very good stuff, but I can’t find it locally and ordering it is pretty expensive. Instead, I grind up the old eggshells and feed them back to the hens.
There’s something undeniably uncomfortable about feeding hens their own eggs, and surely it’s not as nutritionally superior as oystershell, but it’s common practice with apparently no deleterious effect. And of course much cheaper and ‘closed loop.’ I think if chooks have access to good outside ground (not just a few square feet of destroyed dirt) everything becomes less critical, they can forage to fill any gaps. Bugs must be chock full of calcium, right? Not to mention loads of other goodies.
At any rate, I keep an old paper flour bag on the counter for eggshells. When it gets full, all you have to do is smunch the bag to crush them down loosely, then keep filling. (As you are cracking the shells initially, don’t stack them into egg towers, as I used to do. Keep them more or less in singles so that the residual eggy goo can dry instead of rot. This also helps them to crush easier.) When the bag gets a good stock of semi-crushed shells, I take a rolling pin to it. Some rolling, some bashing. Like making bread crumbs. The kids love to help.
I’ve never been clear on how fine the shell needs to be. I have taken it down to almost sand like, but I’m pretty sure that was unnecessary, and a hell of a lot of work. They eat rocks, right? Probably their internal burr grinders can handle bigger pieces of shell. I have settled on taking it to about quick-oat size. Which is still plenty of work, and may still be quite unnecessary. Anyone know the answer here? Feel free to chime in.
After the rolling pin gets old, I take the bag outside onto the concrete patio and bash it with a brick a few times. That seems to finish the job.
I nailed a tuna can to the wall inside the coop for the ground shell, and we keep a yogurt container outside for re-filling from. That’s one of the 4yo’s jobs. These hens don’t seem to eat near so much of it as my hens in Alaska ate, and I suspect it has something to do with this:
This is what they call “gravel” around here, not the sticks part, but the shell part. The entire chook yard looks like this. Might be the whole of what this crazy city is sitting on. I’ve even seen crumbling concrete structures, revealing a filling of this “gravel,” like modern fossils. Anyway, whatever dirt goes along with all that shell must have quite a bit of calcium, nay? So my ground up egg shells may be redundant.
But we keep filling up the can anyway. Can’t hurt right?
[post script: based on some of the comments on this post, I stopped working so hard at this task. Now I just crush them in the bag with my hands and throw them into the chook yard all at once, with some pieces still as big as pennies. Seems fine. They trample them up smaller and eat them over time I guess. Our ladies still lay good strong eggs, so I'm gonna stick with the easy way.]