I use Wellness Senior in small amounts for the rats. It has 17% protein. For the mice, however, I use Drs. Foster & Smith Senior(17-18% I think), plus some non-medicated hog feed, plus some whole grains such as cheerios, puffed wheat/rice, crispy rice, and oatmeal. They do alot better on this mix than on the lab blocks and a MUCH lower cannibalization ratio.

FWIW, I've found the mice don't waste the hog feed as much as the lab blocks, and they just grow alot better on it. I pay about $10 for a 50lb bag.