Personally, I whacked my dog with the dead chicken, but she had an egg inside and it broke all over the dog (scared me, I wondered what I did to him!). When I went towards the hose to clean him up, he dug in his feet when I got close. Went and looked in the weeds, sure enough, another dead bird. He has never killed another chicken, that was about 10 years ago. That being said, we had this discussion on another forum, and this is the advice of a guy who trains dogs:
When it comes to your dog, you can teach him anything as long as you are truly regarded by him as the pack leader, and this would include to not, or to quit, killing chickens.
Contain a chicken so that it can be approached closely with the dog. Take the dog gently and quietly toward the chicken. Curiosity is acceptable, but *any* aggressive move is not.
Absolutely on the very first aggressive move toward the chicken, quickly grab the dog and flip him on his back. Hold him there if he struggles at all. Be aggressive about it yourself if you have to; hold him by the neck and *insist* that he lay still. He is still near the chicken, hopefully can still see it. When he calms, he has submitted to you. A dog on his back is submissive, always.
Now, with a relaxed dog, let him up, and permit him once again to consider the chicken. Talk to him, coo him, let him know as long as he behaves, this is an okay thing. But again, on *any* agressive move, flip him on his back again with a scolding voice. Do this as many times as it takes to get him calm and relaxed and in a totally different frame of mind with the chicken.
Move him away from the chicken, and go play somewhere else. In a little while return him to the chicken, and see if he doesn''t have a totally different perspective with it.
If the dog has killed chickens before, this procedure should be done many times until you feel comfortable that he is relaxed upon approach to a chicken.
Flipping a dog on his back is a key element to any training where one has to assert dominance and convince the dog that you are the dominant one. Not *all* training issues have to do with being on his back, of course. But this is the *very first* thing any dog should learn: you can put him on his back any time you wish, and he must permit it. This includes in your arms. Train him to this first. Get him relaxed being up in the air upside down in your arms. INSIST that he stay there calmly until YOU say he can right himself again. If you do this, it will *amaze* you how easily it is to train the dog to anything you want him to do.
Not to mention, your vet will thank you over and over when you have to take him in for care!