Recent advances toward the practical application of embryo transfer in pigs

Porcine embryo transfer (ET) technology has been in demand for decades because of its potential to provide considerable improvements in pig production with important sanitary, economic, and animal welfare benefits. Despite these advantages, the commercial use of ET is practically nonexistent. However, the two main obstacles hindering the commercial use of ET in pigs in the past several decades (i.e., surgical transfer and embryo preservation) have recently been overcome. A technique for nonsurgical deep-uterine (NsDU) ET of nonsedated gilts and sows, which was seemingly an impossible challenge just a few years ago, is a reality today. The improvements in embryo preservation that have been achieved in recent years and the excellent reproductive performance of the recipients after the NsDU-ET technique coupled with short-term and long-term-stored embryos represent essential progress for the international trade of porcine embryos and the practical use of ET by the pig industry. This review focuses, with an emphasis on our own findings, on the recent advances in embryo preservation and NsDU-ET technologies, which are starting to show potential for application under field conditions.