It can be frustrating and difficult to change them from either mice or asf's if they've been eating them for a long time.

We start all of our hatchlings on asf's and mice and after 3-4 meals they go to straight to rat fuzzy's.
We have never had a hatchling not switch from mice/asf's to rats, it's the ones that are fed those prey items a long time that are difficult to switch.