I often feel like it is easier for us as feeder breeders to produce friendly, healthy pet rats. If we happen to get a rat who is aggressive, bites, antisocial, unhealthy, etc; we do not have to house it forever or find it a forever home in which someone may be unnecessarily burdened because of poor genetics. We are able to cull those that do not make the cut, and quickly get to breeding the best of the best.