Your chickens on soldier flies. In just two weeks of feeding a diet supplemented by Black Soldier Flies, Robert Olivier of Compost Mania is able to increase the egg size by jaw dropping proportions. The egg on the far left is from the store, the egg in the middle was from before enriching the diet, and the egg on the right is now the common size from the flock.
Soldier flied may be the answer you are looking for in your poultry’s diet. Check out the full lecture by Professor Jeff Tomberlin of Texas A&M University given in Hilo Hawai’i on March 13th 2013.