hey bud, i have an anery corn, he's a really healthy adult, he's on small/wheenling rats. (or however you spell it). He's doing great he gets one once a week and he is never lazy or slow to strike it's a matter of 5-10 seconds of me dangling his tasty little dinner in the cage before he's all about it. I don't think rats apposed to mice are any better "nutritionally" It's just a bigger meal. One thing you could try is to feed your corn two mice if your worried about meal size. Two small meals are always better then one large. But my guy is doing great on rats and it seems to be what he really really likes so i'd say try either way.