Maybe emphasis should be on how we can reverse engineer free-range rearing to that predating development of nutritionally complete dietary formulations. If you go back far enough in time you will find poultry raisers that provided little more than protection from predators and cold and the equivalent of scratch and / or table scraps. We now have a lot more knowledge now to target how we can take nutritionally incomplete dietary components to provide an optimal diet for supporting production of free-range chickens.