Current progress in non-surgical embryo transfer with fresh and vitrified/warmed pig embryos

Embryo transfer (ET) should play a critical role in the pig industry because it allows the movement and introduction of new genetic material into a herd with minimal risk of disease transmission and reduced transportation costs. In addition, embryo movement could prevent the potential health and welfare problems associated with transporting live pigs. Although the first successful ET was reported more than 60 years ago, the commercial use of this procedure in pigs is still in its infancy. The surgical requirements for embryo collection and transfer and the difficulties with embryo cryopreservation have prevented its use in pigs, unlike other livestock. However, new methodologies have been developed in the past decade to enable successful non-surgical ET and embryo cryopreservation that could allow the commercial use of ET in the pig industry. This review focuses on the development of these technologies with emphasis on our own findings. Specifically, we discuss the basic aspects of a non-surgical deep-uterine ET procedure and describe several factors that affect its efficacy in the transfer of fresh and short-term cultured embryos. Finally, we conclude with a brief discussion on the use of this procedure with long-term stored embryos.