My dog was a string been until she was about 3 and she's still lean as ever but gets TONS of food and is 100% muscle. She is about 68lbs and standard height. She can easily take down a large man if need be. If you are wanting a guard dog train him for protection, that's the best thing to do. He sounds like he's growing at a normal rate to me and will probably fill out nicely but as others have said, have a fecal done in case, worms are nasty little buggers and I personally would up his food, they have so much energy it amazes me how much Mo can eat and not get fat, man I sure wish I could do that!!!
