Do u put in a bowl or how do u serve. I put egg shell with feed. Normally. But that's not gonna work in this application. I need to keep off floor so can't get dumpedThe larger the calcium particles the better. Egg shells work but oyster is better. The large particles get lodged in the upper digestive tract longer and make contact with the calcium absorption sites in the small intestine at night while the birds are on the roost and when the egg is passing through the shell gland.
While larger than the pulverized calcium in layer feed, crushed egg shells are still pretty small compared to oyster shell.
Here is a good read on the topic.
http://www.nutrecocanada.com/docs/s...-formation-and-eggshell-quality-in-layers.pdf