I own a two and a half year old BullMastiff named Jack. He's always been on the thin side, weighing around 45-50 lbs. He's been wormed recently and found no worms in his stool. I'm looking for a dog food that will help him put on the weight he needs. Right now he is eating Ol' Roy Adult Formula. He despretly needs to put on weight. At this age he should be ranging in between 100-130 lbs. Any Suggestions?