A friend was telling me of an experiement where they would actually do just that Jeff.... not in half, but if you toe clip tigers, you can actually count the rings like you would on a tree. When tigers hibernate in the winter, their growth slows, and then speeds up again in summer, creating "rings".
From what my friend tells me, the study was looking at how paedeomorphic (ones which stay in larval form their whole lives) tiger salamanders live longer and grow larger than terrestrial tigers, and they were finding the age by using the toe clipping method.
If anyone has heard, seen, or know where to find this study, I'd be very interested in reading it. Sorry I cannot back the story up with a source of my own.