Any one familar with the larger Oriental breeds (Kulang Asil, Shamo, exhibition Malay) knows the difficulty of raising such birds without the males going down on the hocks. You can feed them right, give plenty of space and still lose a great specimen between 12 and 16 weeks. They'll be fine today and down tomorrow.
I had an old fellow tell me years ago that it seem to be related to the birds ability to break down and utilize folic acid. I've done my research and found very little information in text books or online. The old man told me to feed yeast beginning at 12 weeks and continue until 16 weeks. He said the yeast would help break down the plants whereby the stag could utilize the folic acid.
I have no way of proving this to be true or false. I can say that when I utilized the yeast I had fewer stags go down. Then I thought, 'do I really want to keep doing this?' Why not just breed for better joints? That proved much more difficult than I anticipated.
Since then, I have also considered giving folic acid capsules to the stags. Maybe a mega-dose would do the trick?
I would seriously like to hear how y'all deal with this issue. I just lost my best Manuel Reynolds Shamo stag. He went down at 16 weeks on near free range.