SEX-RELATED DIFFERENCES IN THE DEVELOPMENTAL RATE OF IN-VITRO MATUREDIN-VITRO FERTILIZED OVINE EMBRYOS

Sex determination of in-vitro matured/in-vitro fertilized ovine embryo s cultured in synthetic oviduct fluid (SOF) medium was performed by th e polymerase chain reaction amplification of specific Y DNA sequences so as to test the influence of sex on developmental growth during the preimplantation period, At 144 h post-insemination, embryos with a bla stocoel were classified as the fast-developing group, whereas those sh owing a blastocoel only after this length of time were classified as t he fast-developing group. At 144 h post-insemination, fast-developing embryos were cultured separately and some were classified according to the size of their blastocoel. At the end of culture (207 h post-insem ination), all embryos were classified according to both their developm ental stage and their morphological quality. The male:female sex ratio of fast-developing embryos was significantly higher than the expected ratio of 50%. More males were observed at the most advanced developme ntal stage at both 144 and 207 h post-insemination. The proportion of males did not differ between the good- and poor-quality groups, althou gh a skewed sex ratio was observed with embryos of better quality at t he most developed stage, In conclusion, embryos at the most developed stage were predominantly male and were derived mainly from the fast-de veloping group, raising the possibility of a deviation in the sex rati o after the transfer of in-vitro matured/in-vitro fertilized ovine emb ryos.