Lab/retreiver that kills chickens?

I have a 2 yr old lab/retreiver who goes over to the neighbors and kills t heir chickens and then brings them home. sometimes eating just the upper body. when he was a pup we had a rott/shepard adult male that chewed a hole in our chicken coop when we were at work with our dog that we have now and they got a couple of them and killed one of our ducks as well. anyways, I do feed them well and I just heard that once they have tasted the blood of a chicken they will always go back to do it again. Does anyone know if this is a fact? and if so, is there anyway to make them stop besides kenneling them, or tying them up?