Well it is true that some BP's won't go from mice to rats and it is also true that the experience of breeders seems to indicate that fed appropriately, both are perfectly good food sources. So basically if your BP likes mice and you don't mind feeding multiple mice, then don't worry about it. If it's easier for you to feed rats and your snake will take rats, then use rats. In the end it's always about what works for the snake and works for you Same pretty much goes for live, pre-killed or frozen prey...whatever your snake will take and take consistently and you can supply conveniently...that's what's best