We have a Great Dane, Brutus, who LOVES his chickens. Our other dog (who has now been re-homed) got a tasting for chicken one day and went after them. He did get one but Brutus defended the entire flock (wish the bird brains knew to hang out by him...he was trying to protect them and they were just wondering around eating oblivious that their siblings were being attacked!) Anyway, the dog that attacked them (A springer spaniel) had been completely fine with them for over 6 months. One day he just got an urge and went with it! I think it truly depends on how faithful you are at training. But I agree it's probably better to stay away from certain breeds....LIKE BIRD DOGS! Man, we're not very smart sometimes!