Before I feed a rat to my snakes, I put it inside a couple of brown paper bags and smack it in the pavement my hardest. Usually that kills them but sometimes it takes a couple more times. When I had boa constrictors I always fed them live prey even as babies. The only reason that I'm begining to feed my bp's freshly killed is cause my boas were always a hassle to take out of their enclosure due to the fact of feeding live prey. I did feed them in different enclosures up until they reached 5ft+, then I couldn't find a box that big to feed them in. Anyways I'm getting off the topic, just knock the rats out, you shouldn't have a problem.