I have seen that they eat it when I put it separate. I mean it disappears, so something is happening to it, LOLThe truth is I don't really see the hens eating the oyster shell which I smash up into even smaller bits. I do feed them their eggshells and at one time when I kept getting shell less eggs I actually ground up my human calcium supplement and saw an obvious improvement right away. Not sure that was advisable but it worked.