It's hard to give a proper answer here, as the dogs' temperaments, personalities, and such are probably a mystery. Its hard to place lables on breeds alone, as any breed can have a drive to chase or kill the chickens. And some breeds with known prey drive may be the best choices and least likely to harm the chickens. It all depends on the individual dogs and not their breed instincts so to speak. We have a 10 year old pit bull who adores my chickens and has no desire whatsoever to chase or harm them. They could sit on her and she wouldn't care. My neighbors chocolate lab loves to chase them and would kill them if he ever gets ahold of one. My chihuahua chases them for fun., as well as the catlle & horse. We've had bird and hunting dogs that wanted to kill, and we've had bird and hunting dogs that could care less about them and even sleep with them. Any breed and any size dog can be a threat, especially those you dont quite know their history with barnyard animals.