I have trained my dogs not to eat my chickens. So far, they're following orders. Elvis, a boxer-pit bull mix, stands in the barnyard and drools as he watches the birds peck around in the grass, but he hasn't tried to kill any of them as of yet.
But lots of visitors come to the farm in the mild seasons, and they're encouraged to bring their dogs. The visiting pooches have not necessarily had the blood thirst trained out of them. Last weekend one of them killed one of my chickens.