unlike everyone else, rosie, i would breed from your petshop rat, keep the first litter and see what problems arise, if none of the babies get problems at 1 y/o then they're likely to be safe to breed from. course it does mean not breeding or not selling any other kits that arise from the parents but only selling from the first litter or first litters kits.
you will also be able to see lifespan of the parents by doing this allowing you to know how long the litters will live. all pedigrees start somewhere
