^^that. Or put easier, 3lbs/day of SC=90lbs/month = little over 2 bags(don't recall 40 or 50lb bags)=37$. RB 1lb/day=30lbs/months=less than a bag=less than 26$ a month.
If he got fat on SC, only 3lbs, he'll do just fine on RB
Other possibility would be some alfalfa or grass pellets, and a vitamin/mineral supplement and his flax mixed in, soaked, of course.
Speaking about flax, a lb of that has tons of calories, too. I feed omega horseshine, 1/2 cup a day. Definitely not a lb. Something to take into consideration