Training your dog not to attack the chickens will require a number of different elements. Can you break a dog from killing chickens? As soon as he goes for the chickens, say 'STOP' loudly and firmly so he knows you mean business. Keep an eye on your dog's behavior and wait for him to pull or lunge. Once they are both safe and secure, slowly head over to the chickens. Secure your dog to the leash and safely stow your chickens in a coop.