Rederivation is a process that aims to remove disease-causing pathogens from mouse lines. Rederivation is performed by embryo transfer or hysterectomy section (commonly referred to as C-section). Unborn embryos or near term foetuses are removed from their mothers prior to birth and placed with recipient or foster females. This process eliminates the transfer of micro-organisms from the mother to the pups.

While embryo rederivation is the method of choice to eliminate pathogens, hysterectomy section may be performed on lines that breed poorly or have a mixed or uncommon background that don't respond well to the hormonal treatment used in embryo rederivations.

After rederivation the foster or recipient females as well as the rederived progeny undergo health screening to ensure that all disease-causing pathogens have been removed from the line. Only mice with a clean health screen are moved into the main breeding colonies in the biobubble pavilion.