nothing irks me more then that person that spews nothing but nonsense about how "feeding live prey is horrible, wrong & evil!" you have to feed what your snake will eat, simple as that.
my mojo girl will ONLY eat live & if offered dead she looks at me like "hey i did not kill that so dont expect me to eat it." i swear she turns her nose up at it as if i've insulted her somehow. so that "feed f/t or pre killed prey only" thing is a load of crock for those that have animals that will only take live.
now lemme clarify those that are successfully feeding f/t or prekilled, awesome & i hope you continue having success doing so but for me i'm stuck with what my girl will take. in fact she just ate today after not having eaten for a month & i had to go down to very young rat pups, crawlers with their eyes still closed. my snake ate the 1st one but now i have to hand feed the 2nd little one for anther 2 weeks before i offer it again.
granted my snake has not been bitten by a rat yet but there have been a couple that have gotten defensive & 1 pounced on my snake's head & she didnt eat for 3 weeks cuz of that. i watch her feedings VERY closely & once i sit down to start a feeding i dont leave from that spot until she's either done & retreated to a hide to digest, if she's eaten. i only leave the rat in long enough for the snake to decide if she's gonna eat it & the second she shies away from it i promptly remove the rat, that way the rat doesnt have time to think about getting defensive or aggressive towards my snake.
about prey size though, the general rule of thumb is the prey should be slightly smaller then or equal to the size of the thickest part of the snakes body but preferrably the slightly smaller. my girl only takes prey smaller then her thickest part & i'm fine with that as long as she just eats. this having to get very young pups thing was only done cuz its been so long since she last ate & i had to go small so as to not overwhelm her system. i'll have to work her back up to weaned rats or the smallest of the smalls again, which is what she was taking before she went on this month long no feeding thing. i'm fairly able to correctly visually gauge the sizes of rats i need, for the most part.
so again, dont fall into that fear trap that those store employees like to throw you into. you do what you have to do with whatever your snake chooses to take & stick to it. your doing what you have to do to care for your pet & no one has the right to tell you what your doing is wrong.