I feed all of my ball pythons live, and take the rats out after an hour if not eaten. I have never had any issues. I was listening to reptile radio, and BHB said that he feeds all of his balls live, and leaves the rats in overnight, and never has any issues either. I imagine that he has a TON of ball pythons too, and that he has been doing this for years.

I used to feed f/t. The best way to do this is to thaw the rat out to room temp before heating it up. This may solve your problem.

To prekill, you can use carbon dioxide in solid or gas form. That will first put them to sleep, then kill them. You can also sever their spine, as the poster above stated.