Alternative breeding strategy in which three to four adult females are co-housed with one adult male resulting in multiple pregnancies. All but one female must be removed from the cage prior to the birth of any pups. Justification to house two adult females, one adult male, and two litters in the cage as described by the definition of trio birthing may be submitted to the IACUC. Singly housed pregnant females or stud males should be labeled with a blue tab as described in the Identifying Single Housed Animals SOP.