I lost a silkie yesterday to my terrier....was posting on the Utah thread, it is so sad. I have had problems with my dog for 3 yrs, we have to keep him in the house or have him go potty in the front, no pottying in the back yard. My son let him out yesterday and just forgot. Grrr. I am so sorry for your loss, it really sucks. I do believe that once they taste it, they are always a threat, mine won't quit. I would have sold him two years ago but he is otherwise very sweet and my kids would not want him to go. He just sees the chickens and his eyes glaze over and he hears no voices after that no matter how loud we yell at him. Funny thing, he does not really eat them, he shakes them to death, I think he feels like when they get "out of the run" they are a threat to us and is protecting us from them. He will not let any other critters into the yard, and is very protective at the front door. The good side...I HATE snakes, and we get them often, if i find a snake I turn him loose and tell him "go get the bad guys", and he shreds the snakes to bits. He is a great watchdog, but we have to really watch him around the hens, he will dig sometimes even to get into the run.
ETA: Mine has killed a few quail too so be careful.