That's what I've heard is a major causer, but the grain I buy isn't lacking in that, and the chicken recovered without a food change. But that's great that your vaulted do so wellWell I'm glad your little one is recovering. I've been breeding silkies for 8+ years and have had the occasional vaulted skull and never had a problem. Mine free range with large fowl and they manage to keep out of trouble. In my experience wry neck is more often than not a thiamine B1 deficiency.