It is not always clear what causes wry neck symptoms. It can be hereditary, a sign of head or neck injury, vitamin E or B1 thiamine deficiency, and is seen in some diseases, such as Mareks and a few others. It is not always responsive to vitamins. I have a rooster who developed it a couple of years ago. He only does it when resting or sleeping. He gets a balanced diet and was treated with vitamins with no improvement. He stays with one hen away from the bigger flock, but I am thinking of putting them together since we no longer have another rooster.