Mack is 7&1/2 years old. His vertebrae are fusing, his whole spine is pretty much involved. He gets a doggie dose of asprin for that. Last spring we found out he had an irregular heartbeat so he takes a heart medication. My concern is he is getting so grumpy. He growls at his 4 year old "brother", Ruggles. Ruggles responds by totally backing off whatever they were doing and takes shelter by me or leaves the room. I can tell Ruggles' feelings are hurt. Mack also growls at the cat when he is on my lap and she wants up on my lap too. He used to welcome Katze (cat) and enjoy snuggling her. Could Mack know his health is going downhill and is trying to remain top dog by growling at his furry siblings? There has been no fighting, just Mack growling. Should I not worry about it because there is no fighting? Ruggles has a wonderful temperment; he is Bulldog # 6 and has the best temperment of all.