Is my JRT underweight?

I have a one and a half year old JRT male. I have not been able to find any advice relating to my question. My Jack is of slightly smaller stature than what I would view as the norm for the breed. Other Jack's I know are more full bodied (not fat) than mine. My Jack weighs 12 lbs and appears so thin. His ribs stick out on both sides. I recognize the breed to be muscular, but he has a body style more of a whippet than what I've seen of JRT's. He eats approx a cup or cup and a half of Purina Dog chow a day. He does not eat it heartily, but anything he eats seems to be ran off by all his outdoor exercise. Do you have any suggestions as to what to feed him to promote a slight weight gain? I have asked two different vets opinions, one told me the dog would decide how much he would eat and it was not something I could control, the other said I would just need to accept the fact that I have an active breed. I am sure I need a more JRT knowledgeable vet, but what can I do for now?

• Re: Is my JRT underweight? Jun 27 (0)