We have a female who will soon (in June) be 11 years old. She’s always been between 50-55 lbs. She’s just a small Boxer, especially compared to our 8 year old male who is 70 lbs. of solid muscle. We have only ever fed our Boxers Royal Canin Boxer formula. Trigger: We did lose our 80 lb. male last year to lymphoma. His demise was rapid though and he was basically skin and bones in a short 3 month’s time.