I have a few thousand rats on pine right now. They're doing a lot better than the ones in the freezer LOL. Personally, if they breed well, and live at least 64 weeks, I don't care what happens to their liver. I use kiln dried pine and I have only lost one adult rat in the last as long as I can remember and she died in child birth. I did find a rat pup dead the other day with a bunch of shavings in his mouth, but I'm betting that he was just retarded and tried to eat a bunch of bedding. It happens sometimes.

For the record, I have had ZERO problems with pine shavings. I use kiln dried pine shavings and they are cheap, plentiful, and have worked for me 100% of the time.