Advances and limitations of in vitro embryo production in sheep and goats

This review summarizes the latest advances and main limitations for the implementation of in vitro embryo production programs in sheep and goats. We describe the laparoscopic assisted technique for oocyte retrieval and propose new insights for follicular manipulation to improve oocyte quality. Further description of the routine conducted in our laboratory for the in vitro process of oocyte maturation, fertilization and embryo culture is presented, with emphasis in the main issues for the success of the technique. Protocols for fixed time embryo transfer (FTET) are proposed and the optimal number of in vitro produced (IVP) embryos to be transferred per female is discussed. In addition, we present pregnancy outcomes and birth rates recently obtained with FTET with IVP embryos cryopreserved by vitrification with new minimum volume methods. In summary, due to important refinements for in vitro embryo production in sheep and goats achieved in the recent years, this technology is now available for its implementation in commercial programs for genetic improvement, for the production of genetically engineered sheep and goats, and for basic research in reproduction.