Hello! I have a now 10 week old black lab puppy. My brother’s 3 year old dog (mutt, unsure of breed) is extremely jealous and has gone after the puppy growling and barking and biting her(not playful) 5 times now. We live together so it’s hard to separate them all the time without the adult getting upset. They will play sometimes however the puppy has her hackles up. Now when she plays with other puppies she seems very aggressive and has her hackles up as well. I’m not sure if she has adopted this aggressive behavior or if it is normal puppy play. I am very concerned and do not want an aggressive pure bred lab.