Commercial feeds intended for raising and fattening poultry for human consumption were not meant for game birds. Even the feeds manufactured for game birds are suspected to not be formulated for optimum nutrition in peafowl.
It isn't just the cross-breeding with Greens and Spaldings but living conditions including feed have dramatically changed the IB to its present physical condition. Even if not cross-bred being kept in small enclosures and fed a poor diet, one that was intended to fatten up birds for slaughter...