The only problem with heating your rabbits in the winter, especially ones that live outside is, once the heat wares of your bunny catches a chill, i beleive heating a rabbit is the worse thing to do, i leave my rabbits to grow their thick winter coats, my rabbits are in a garage, its the same temp as outside except it keeps the drafts out, i give them plenty of bedding, hay , straw and feed them more, apart from that they get through it themselves with regular excersise outside to warm them up a bit.
My cousin had a rabbit she used to bring it in the house for a run around, and gave it a heta pad for at night, but as soon as that heat went the rabbit got cold, it eventually caught a chill, developed neumonia (sp?) and died :?
This is only my personal opinion, i'm not judging anyone :wink: