It would really depend if your cat is a good killer/eater or not. My cat used to catch a mouse and then just start gobbling it down, it's quite messy feeding a fresh kill. I give her prekilled ones now, both to avoid the mess and because now she has gotten lazy, she'll catch the mouse, carry it around for a bit, get tired, drop it, catch it, start all over. You don't want mice running loose in your house and that's not a very humane situation for the it either. You'd have to step in and kill it yourself quick if the cat doesn't and it's not always easy to get a live mouse back out of a cat's mouth if you need to, trust me. I do give her live pinks sometimes but she eats them right away and it doesn't seem any kinder to freeze them first.