We've been feeding Maggie and Lucy this same diet for over a year. The girls have pretty much maintained their weights for the last 6 months on it. Maggie is just under 2 years, and Lucy is 16 months, so their growth has slowed, anyhow. They are each right around 28-1/2 inches tall.
What I was told, is to increase the oatmeal (it's a fatty grain), and add a little more meat to the meat meal, if your dog needs to gain weight. Keep the other ingredients and supplements at the levels recommended for their weights.
Is he very active? Lucy runs like a greyhound, and it's very hard to put/keep weight on the girl.....although her muscle tone is that of an athlete. She weighs right around 115 pounds, and I feed her roughly TWICE as much oats and meat as what I give Maggie. Maggie has severe hip displasia and isn't as active, although we do exercise her every day. Even though Mags weighs around 125, I give her the amount of oats and meat recommended for a 100 pound dog, and she maintains well on that.
Also, once a week I feed the girls their favorite meal. Cook brown rice and sliced sweet potatoes, until both are just tender. Drain, and add Jack Mackerel and Salmon (I buy the canned kind at the grocery store, in the "human" section). Mix the fish into the rice and sweet potatoes. Feed. This is their favorite dinner. Not exactly raw, but they love it.
Check for parasites, if that's a concern, then try increasing the oats and meat for a few weeks to see if that makes a difference. Good luck!
