I used to not even look at the feeders. I just go to the store and ask for one and they hand it to me in a box. When I got home I would just open the lid and dump it in. I never laid eyes on it till it was in with the snake.

Now I pre-kill them with CO2. I dump the mouse into a ziplock bag. I have a little CO2 tank that I used to use for paintball. I stick the hose in the bag and turn on the air. The mouse is asleep within about 15 seconds. Then I dangle it in front of the snake and she doesn't know the difference.