Meh, if the dog is a biter and has gotten the taste of live blood (chicken), you won't ever really change them.
My mother had an English sheep dog she really loved. Came down to the barn and there is a pile of goose feathers. Tried a shock collar, many things but the dog would kill something. Then it happened again and my mother hung this dog by the neck and I could see its eyes begin to glaze over in death when she dropped it free. The dog did ok for a good bit after that. Maybe a year. But sure enough, one day my mother goes to the barn and there are several piles of goose feathers. She took that dog out and shot it. It was her pet.
Two lessons
1. once the taste of blood is there, it never leaves and you pretty much need to put the animal down if it is going to be a danger to the rest of your livestock or give it to a place that its not an issue.
2 BEST NOT MESS WITH MY MOTHER!