Co-transfer of parthenogenotes and single porcine embryos leads to full-term development of the embryos

It has long been known that several embryos are needed to establish and maintain pregnancy during early gestation in pigs. In this study, we assessed whether co-transfer of parthenogenotes with a single embryo was sufficient to maintain development of the embryo. Embryos were recovered at morula and early blastocyst stages from gilts that had been artificially inseminated. Parthenogenotes were produced from oocytes matured in vitro, activated by electrical stimulation, and then cultured for 110h. Those that had developed to morula- or blastocyst-like stages at 110h post-activation were transferred to recipient pigs either with or without morula or blastocyst stage embryos. Parthenogenotes that were transferred to recipients in the absence of embryos were viable up to 30 days post-activation and formed limb-buds; at 40 days, however, all were dead or degenerate. Among pigs that received both parthenogenotes and a single embryo, seven of nine (77.8%) delivered a normal piglet at full-term. This study therefore demonstrates that parthenogenotes can be used in place of embryos to establish pregnancy and promote development of a single co-transferred embryo. This method may be applied to rescue high value porcine embryos that are difficult to produce, such as transgenic cloned embryos, or for embryos frozen as a genetic resource.