Quick article here:
http://www.kingsnake.com/articles/PreKilledPrey.html
The quickest benefits of f/t for me:
-all the food is in the freezer, making it easier to feed everyone when *I* want to and not when I have time to go out to the store
-this is negated if you raise your own, but f/t rodents are always cheaper than buying live from a petstore
-nearly all mites/parasites/diseases on the mice are killed with the freeze
-not such a deal with ball pythons, but other snakes will calm down overall if switched to f/t
-minimally noteworthy, but I'll put it here anyway. It's more humane to the food to be killed by CO2 than bitten and strangled.
-stubborn feeders can be left with their food overnight with no danger
-the last and biggest: immediate physical danger. Lots of people will say that live is okay because they monitor the feeding and are willing to go in if the snake is in danger. I have heard too many stories about snakes, even a huge burm in one case, killed with one extremely well placed bite by the prey animal directly to the head. Barring fatality, bite wounds to the mouth, body and eyes are also a possibility. And barring the vet bill those could all cause, my snakes are my pets first and foremost so if there's an easy way to avoid endangering them, I will take that path.
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1.0 speckled kingsnake
1.0 leucistic texas ratsnake
0.1 tricolor hognose
0.1 water python
0.1 spider ball python
1.0 green tree python