It has been my experience that a breeder will switch them from mice to rats, but not all breeders can do the f/t switch because they raise their own rodents.

That said, I have only one snake right now who is eating live mice. All the rest are eating f/t rats with no issue. If she continues to stay on mice I'll just need to deal with that- and find a less expensive outlet for live mice

So, I guess I'm suggesting that most snakes can be converted to f/t and from mice to rats. A few, though, don't seem willing...