I feed mine Fromms All Life Stages from their Four Star Line. He's been on this for about 1 1/2 years now and has worked great; no gas, good stools.
I rotate between the ones offered in their Four Star Line.
With his evening meal, I also add in a small bit of canned food. Either Fromms, Merrick, or Wellness
Fromm Family Foods - Four-Star Duck & Sweet Potato Holistic Entree