i think above they were saying that a rat the same size as a mouse is not going to be nearly as aggressive. at that size they barly know whats going on. i have a ball python that will only eat live, she gets bit sometimes but they heal after the next shed. i have had to smack a few rats when she grabbed them the wrong way tho and they had free range to bite the crap outta her, i didn't take chances, couple flicks to the head stuns them, sorry but your not biting my snake.
i think most problems are when the snake doesn't eat and the rat chews on the snake because theres no food