Embryo collection and transfer in pigs were initially primarily performed for research purposes. Commercial embryo collection and transfer in pigs is not yet done as intensively as in ruminants Embryo Transfer in Cattle Although collection of a single embryo is occasionally done in cattle, most embryo transfers in cattle are done after a hormonal treatment to superovulate donor cows and to maximize recovery... read more and horses Embryo Transfer in Horses Embryo transfer in the equine industry has been primarily used to obtain offspring from mares with restricted reproductive potential (mares with undiagnosed subfertility, uterine disease, or... read more . It is also underreported.
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; however, they require specialized equipment and skill. Embryos are typically collected 5–6 days after ovulation and transferred preferably to recipients that were in estrus ~24 hours after the donor sow. 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. It is expected that once non-surgical procedures are validated for embryo collection and transfer in the field, the pig embryo industry will grow at a rapid pace as has already occurred with cattle and horses.