Once a dog tastes the blood, it is almost impossible to stop this behaviour. You can tie chicken that it has killed until they rot off the color. You can use the shockcollor, but it is darn near impossible to catch them in the act and this becomes as useless as anything else. You can tie him up. Now that will work. Most people will not do this and there is alwayst the occansional opps, and a dead chicken is again found. You can keep your chickens in an encloser for the rest of their lifes or get rid of them. I have a Corgi dog that is older, she is out and about with the chickens ALL the time. She has NEVER even looked at them twice. Why ? We trailned her from an early age, it took months of hard work, but now we have a dog and chickens. Most people will not take the time to train early and the dog or the chicikens end up dead. It is too late to train your pit bull, it has already killed. You can try an electric fence and collar, but I have seen dogs run right throught these things, especially after a flapping clucking play toy.