I agree that chickens do not need a vegetarian-based diet. I, too, laugh at the commercials on TV that "brag" about feeding vegetarian diets! Those poor chickens!
My free range flock will eat anything that does not outrun them - frogs, snakes, lizards, worms, bugs, even mice! They also get any leftovers from the house - all types of meat included. They LOVE salmon skins and leftover salmon! I toss it all out, bones and all, even chicken and turkey carcasses, and they clean every bit of meat and cartilage off. Yum!