I have noticed that a lot of large breed cockerels have sudden lameness issues, I have had 3 of them since I have had chickens suddenly go lame on one leg. Mine are Orpingtons mostly of english import lines. None of the 3 were related. 1 of them was not from english lines but was a very large cockerel. The are just suddenly lame and unable to walk, no apparent injuries. having a discussion with friends I am guessing it might be nutrition and growth related, perhaps common in large breeds. all have gotten over it and walk without a limp, just took some time and rest. My 3 were all under 6 months of age and growing like mad when it happened. I feed layer crumbles and scratch or wet COB (corn oats barley with molasses) lots of kitchen scraps, mostly meat. they also free range daily for grass and bugs. I wanted to know more so searched on here and found more posts about young cockerels with sudden lameness. most were large breed. Is it something lacking in nutrition? or do they just grow so large so fast that joints cant keep up? someone suggested for the really big fast growers that Turkey starter might help, higher protein was the thought. I am not real scientific when it comes to feeding the chickens, they get what they get and they all do fine on it. I would find something better if they did poorly... Anyway, maybe the cause is lack of protein or to much protein? or the size and growth? what do the experts out there know?