If you are feeding raw??, lay of the red meat, and just give him white meat,chicken rabbit.
If a dog is worked a lot or kept outside in cold conditions or highly strung,or maybe all three and more, a red meat diet(-20) would be recommended, but if they are worked lightly, only once or twice a week/live,sleep, in worm conditions then white meat with a lot less fat content, would be better, as they only need the extra fat if they are burning it of.
But you have a much easier problem to solve, than a dog, that has trouble keeping the weight on.
Happy Hunting