Just a thought but I'm wondering if the way I thawed the f/t rat had some bearing on the regurgitation. I used the same techniques which I've used on the f/t mice. Thaw in the Fridge for several hours and then place the rat/mouse at room temp near the enclosure for 2-3 hours. Then I hit the rat w/ a hair dryer for 20-30 seconds. The rat felt like he was thawed but maybe there is a better 'sure' way to prepare a f/t.