First of,,,,,,,,
Shell less eggs usually means a chicken is not getting enough calcium in diet. If you tried to do ALL you can to provide more calcium, then maybe chickens' metabolism, is not able to utilize the calcium.
At witch point I have no idea for solution.
Sometimes having oyster shells free choice does not work as should in a Perfect Universe. I have mixed quantities of it into my feed pellets. (I use Alflock 2% calcium because I have layers and non layers)
The chickens will usually just leave the shells on the bottom of feed bowl, but will consume some as well. It is a way for them to be encouraged to take some in. Your chickens will not OVER DOSE on calcium when it is solid cracked oyster shells. Any extra, will just go thru chicken.
Processed calcium in layer feed at 4%, fed to non laying chickens and roosters does have the potential to do those harm. (kidney and liver)
I am not saying this to sound an alarm and scare chicken keepers of a doomsday. Most chickens do not live long enough to be really affected by someone feeding their mixed flock of layer, and non layers a layer feed. I keep chickens as pets only , and they all live long lives and make the Rainbow Bridge Transition Naturally.
