We have a four month old Corgi puppy. He's a sweetheart and is doing great on his obedience. But recently I bought he spent a week at my sisters with her three crazy dogs. He came back getting a bit aggressive over treats. He snapped at another dog in a pet store who went near his treat. I bought him some raw beef bones. He growled when you went near him with it. We took it off of him. Now we give it to him, if he growls we take it from him. In a few minutes we give it back. We do this several times until he lets us take it freely and walk all around him. He is good for awhile and then he growls about it again. Any tips?