Yes my silkies LOVE the FF. I drain it from water well for the silkies, so it is an oatmeal consistency. I do notice changes. Their feathers look nicer, Pearl lays bigger - stronger eggs, and their poop is firm and smell free. They were never sick, so I can't say it improved their health, but it sure helps my pocket bookACV is not known to help cure wry neck. However, it will help with the overall health of the bird.
Braggs is another common brand of organic ACV, which my local grocery store is starting to carry. It's hidden in the natural food section instead of with the regular vinegars.
Aoxa,
Are you feeding your silkies the fermented feed? Do you see a positive change in them? I subscribed to the Fermented Feed thread but just haven't had time to get past the first few pages.
Tina

And their faces when I serve it.. They are really happy with the feed. They go nuts!