Reproductive Biotechnologies Applied to the Female Sheep and Goat

Abstract

AbstractApplying reproductive biotechnologies to female sheep and goats allows to improving animal protein production, advancing scientific knowledge with the use of small ruminants as animal models; and developing innovative biomedicine technologies. Multiple ovulation and embryo transfer (MOET), in vitro embryo production (IVP) and embryo sexing and cryopreservation, are some of the biotechnologies available for use. The control of the estrous cycle, the prediction of multiple ovulation results, and the difficulty in performing non-surgical embryo recovery procedures are the major chokepoints in MOET programs. Whereas oocyte quality and efficiency upon the use of defined media is a concern in IVP. Embryo survival after cryopreservation should be strengthened, especially in IVP embryos. More advanced reproductive biotechnologies, such as cloning by somatic cell nuclear transfer (SCNT), are increasingly being conducted in small ruminants. SCNT is a possible step for the production of transgenic animals, however, more advanced resources for performing transgenesis are being developed, and were already applied to small ruminants.Here, we review reproductive biotechnologies in female sheep and goats. Deeper understanding on the control of estrous cycle and progress regarding the non-invasive transcervical embryo recovery have been achieved. Regarding IVP, the current outcomes reached in small ruminants are similar to the results obtained in bovine, allowing a safe application of this embryo production technique for commercial ovine and caprine production systems. Importantly, significant advancement has been achieved regarding survival after cryopreservation and establishment of pregnancy, especially in MOET-derived embryos. Regarding SCNT, attempts have been focused both on establishing the appropriate conditions for obtaining karyoplasts, cytoplasts, and on performing adjustments before and after embryonic reconstruction. For performing transgenesis, the easy and non-expensive molecular-based approaches, such as the CRISPR/Cas9 system, were made accessible to many research groups and industry, and had undoubtfully revolutionized the production of bioreactor animals.KeywordsCloningCryopreservationin vitro embryo productionin vivo embryo productionIVFMOETSCNTSuperovulationTransgenesisVitrification