Hairless rats do not make good feeder breeders. They should definitely be left for just pets. They have high instances of not lactating, and they also need higher protein and warmer environments to make up for the lack in fur.

Self is the non existance of a marked gene. It's the default template I suppose you could call it. If there is any marked genes or modifiers in the parents, chances are you will never see a self.

Here's a page with some explanations of markers and modifiers
http://www.curiosityrats.com/geneticsmarkings.html