Embryo Transfer in Pigs
Embryo collection and transfer in pigs is not yet done commercially or as intensively as in ruminants. Until recently, embryo transfer in pigs was primarily performed for research purposes. In 2012, Canada, France, and Ireland were the only countries to report the commercial collection and transfer of 2,478 swine embryos. Owing to the high ovulatory rate in sows, superovulation treatment may or may not be used in embryo transfer procedures. Embryo collection can be done soon after a genetically valuable sow is slaughtered and the reproductive tract is collected for embryo retrieval. Surgical collection of embryos is also performed using ventral laparotomy of the caudal abdomen. Most embryo transfers are performed using surgical techniques (abdominal ventral laparotomy under general anesthesia). Recently, nonsurgical techniques to collect and transfer porcine embryos have been developed and proved successful, but they require specialized equipment and highly skilled individuals. Embryos are typically collected 4–7 days after ovulation. Current pregnancy rates with nonsurgical techniques remain lower than those obtained after surgical embryo transfers. Embryos should not be transferred to the uterine body, because this results in low pregnancy rates. The transfer of 16–22 embryos per recipient is recommended to achieve optimal pregnancy rates.