Achievements and future perspectives of embryo transfer technology in pigs

Abstract

Commercial embryo transfer (ET) has unprecedented productive and economic implications for the pig sector. However, pig ET has been considered utopian for decades mainly because of the requirements of surgical techniques for embryo collection and embryo deposition into recipients, alongside challenges to preserve embryos. This situation has drastically changed in the last decade since the current technology allows non-surgical ET and short-and long-term embryo preservation. Here, we provide a brief review of the improvements in porcine ET achieved by our laboratory in the past 20 years. This review includes several aspects of non-surgical ET technology and different issues affecting ET programmes and embryo preservation systems.The future perspectives of ET technology are also considered. We will refer only to embryos produced in vivo since they are the only type of embryos with possible short-term use in pig production. K E Y W O R D Sembryo storage, embryo transfer, porcine, vitrification | 5 MARTINEZ ET Al.

Reproductive fluids, used for the in vitro production of pig embryos, result in healthy offspring and avoid aberrant placental expression of PEG3 and LUM.

“…This is, on the other hand, other crucial factor to be considered because all the above referred rates derive from embryos produced in vivo and ours were produced in vitro. In fact, for most of the researchers, the transfer of embryos produced in vivo (but not in vitro) is the only one with "possible short-term use in pig production" [32] although, from our results, this statement should probably be reconsidered since our pregnancy rates are comparable to those obtained transferring in vivo collected embryos.…”

“…As it has been recently proposed, this could be associated to a dysregulation of pro and anti-in ammatory cytokine levels in recipient sows that, in turn, induce embryonic mortality [31]. However, many other factors related to either the quality of the embryos or the recipient's status and age could have been affecting these rates of unsuccessful transfers [32]. On the one hand, and as for the own ET procedure, the reported levels of embryonic mortality by using nonsurgical procedures are approximately of 70% [33,34], while using surgical laparoscopic procedures, Wieczorek et al [35] reported 50% of successful pregnancies but those were after transferring in vivo produced embryos.…”

Vitrification of in Vivo-derived Porcine Morulae and Blastocysts Alters Metabolic and Stress Response Pathway Alterations

“…Cryopreservation [1][2][3] of porcine embryos has essential applications for agriculture and biomedical research, since it is the best way to store valuable genetic material (reviewed in [4,5]). Pig embryos have been challenging to cryopreserve due to their high amount of cytoplasmic lipids, which results in extreme chilling sensitivity [6], but signi cant advances have been made for this technique, thanks to the development of vitri cation protocols (reviewed in [5,[7][8][9][10]).…”

“…Cryopreservation [1][2][3] of porcine embryos has essential applications for agriculture and biomedical research, since it is the best way to store valuable genetic material (reviewed in [4,5]). Pig embryos have been challenging to cryopreserve due to their high amount of cytoplasmic lipids, which results in extreme chilling sensitivity [6], but signi cant advances have been made for this technique, thanks to the development of vitri cation protocols (reviewed in [5,[7][8][9][10]). The implementation of vitri cation protocols, particularly the open pulled straw (OPS) system [11] using super ne OPS (SOPS; [12] straws, has provided excellent viability in vitro reaching > 80% with vitri ed morulae and > 90%) in blastocysts [1][2][3]; further, encouraging farrowing rates (range: 38.9-75%) have been achieved after nonsurgical [13][14][15] and surgical [15,16] transfer of vitri ed morulae and blastocysts.…”

Impact of Embryo Transfer on the phenotype of the offspring in pigs

“…Aside from being an excellent model to study human reproduction, the use of ART in pigs may also be useful at a more commercial level to increase meat production -but apart from AI, these systems are still far from being widely established in the pig industry [7]. The development and extended use of some speci c technologies such as ET would not only provide greater genetic selection, but would also decrease the risk of diseases transmission since it avoids the entry of new animals in breeding centres and farms, decrease transportation costs and minimize the effect on animal welfare during transportation (reviewed by [8]). However, ET technique shows some limitations in porcine species since it requires the collection of a large number of viable embryos (ideally cryopreserved) to be transferred to the recipient mothers and, until recent years, it also required the surgical transfer of those embryos [9].…”