At what point (size or age) does it become appropriate to start feeding a Bp rats instead of mice? I still have my Bp (just under a year old) feeding on mice, although I usually feed him once every 4 or 5 days because the mice are now smaller than the thickest part of his body. Most rats that i see in stores however, are still thicker than his body so i am hesitant to feed him one. Any recommendations?