i agree that until you know how an animal is going to be, they shouldn't be left unsupervised around any other animals. That being said not all dogs will attack chickens when ever they get a chance. Our dog was older when we got chickens but we've never had any problems with her and any of our other animals. We've never had to train her or anything. However, I would say that she is the exception rather than the rule. I totally trust her around our chickens. She actually cracks walnuts open for them. Most so they'll leave her alone.