I would be leary of it. If not the heat, I would worry about the electrical factor (a short, or chewing on the coard, etc.) But obviously, they would love it. If you did use one, I would make sure that there were a couple of layers of blanket between them and the heating pad.
I have seen "self-warming" blankets for pets. They reflect the animal's own body heat back to them. I think I would feel better about them.
..... this is coming from someone who LOVES electric blankets.
