My 9 month old Rottweiler recently started limping on his front leg, and has no outward signs of injury, so we took him to a vet. Now, this is the first time we've taken him since he got his last set of shots until he's a year old, so he was pretty excited. He was panting a lot, and pacing around, but not acting aggressive toward anyone. And then when the veterinarian wanted to listen to his heartbeat, she asked her assistant to hold his mouth shut. Now normally, Aries doesn't show any signs of aggression. I mean, if he squeaks a squeaky toy he'll let go because he thinks he hurt it. But when the vet tech tried to hold his mouth shut, he lifted his lip and growled at her. Immediately the vet said to get a muzzle, and started berating us, telling us that our dog "thinks he's boss" and could turn on us when he gets older. But I can't help but think that he just couldn't breathe! He was panting extremely hard when this all took place. So I was just wondering if anyone else had a similar experience? We're going to get a head harness and a muzzle to get him used to have things around his mouth, but any other advice would be appreciated.