I've seen some Youtube videos and internet posts about people that breed rats but then insist on still freezing them and thawing them before feeding to "kill parasites." How big a concern is this? I'd like to start a small colony in my shed with the intention to feed freshly killed prey to my snakes. Freezing them ahead of time (aside from when you have too many) would seem to defeat much of the purpose of raising rats to begin with.