Xenogenous fertilization of equine oocytes following recovery from slaughterhouse ovaries and in vitro maturation

The in vitro production (IVP) of equine embryos using currently available protocols has met limited success; therefore investigations into alternative approaches to IVP are justified. The objective of this study was to evaluate the feasibility of xenogenous fertilization and early embryo development of in vitro matured (IVM) equine oocytes. Follicular aspirations followed by slicing of ovarian tissue were performed on 202 equine ovaries obtained from an abattoir. A total of 667 oocytes (3.3 per ovary) were recovered from 1023 follicles (recovery rate, 65%). Oocytes underwent IVM for 41 +/- 2 h (mean +/- S.D.), before being subjected to xenogenous gamete intrafallopian transfer (XGIFT). An average of 13 +/- 0.8 oocytes and 40x10(3) spermatozoa per oocyte were transferred into 20 oviducts of ewes. Fourteen percent of transferred oocytes (36/259) were recovered between 2 and 7 days post-XGIFT and 36% of those recovered displayed embryonic development ranging from the 2-cell to the blastocyst stage. Fertilization following XGIFT was also demonstrated by the detection of zinc finger protein Y (ZFY) loci. Ligation of the uterotubal junction (UTJ), ovarian structures, or the duration of oviductal incubation did not significantly affect the frequency of embryonic development or recovery of oocytes/embryos after XGIFT. In conclusion, equine embryos can be produced in a smaller non-equine species that is easier for handling.