I don't grow my own food. But from watching other threads and peoples ideas on how to humanely kill rodents. The fastest, most humane way would be to break their neck (snaping the cervical spine, I think thats the technical way to say it, but I could be wrong.) I have been told by more than one person (not only on this site, but from other pet stores *a very good one* ) that freezing them like crystalizes their blood and makes it a painful death. But I could be wrong, you will get a lot of people on here saying alot of things, it is usually based on your own expierences and opinons.
Neptune, Zion, Enigma,