DEVELOPMENT OF IN-VITRO MATURED AND FERTILIZED BOVINE EMBRYOS, CULTURED FROM DAYS 1-5 POST INSEMINATION IN EITHER MENEZO-B2 MEDIUM OR IN HEMC-6 MEDIUM

Bovine embryos were produced by in vitro maturation and fertilization of abattoir oocytes. The embryos were randomly allocated either to coc ulture with bovine oviduct cells in Menezo-B2 medium (control group), or to culture in the defined HECM-6 medium. At Day 5 after inseminatio n the HECM-6 embryos were transferred to Menezo-B2 medium with (HECM-B 2/BOEC) or without (HECM-B2) oviduct cells for further culture. The pr oportion of cleaved embryos and blastocysts, the morphology and the sp eed of development were compared for the control and HECM groups. Sign ificantly more HECM-6 embryos than control embryos cleaved (88+/-3% vs 76+/-5% (+/-SD)). Significantly fewer blastocysts developed in the HE CM-B2 than in the control group (28+/-2% vs 35+/-3%), in addition the speed of development was delayed and the morphology was impaired. In t he HECM-B2/BOEC group no differences in neither morphology, blastocyst rates (31+/-8%) nor speed of development could be demonstrated, when compared with the control group. A portion of the control and HECM-B2 embryos were vitrified at Days 7-8, but no differences were noted in s urvival or morphology at 48 and 72 h post thawing. It can be concluded , that the defined medium HECM-6 can support bovine embryonic developm ent through the 8-16 cell in vitro block stage without the use of cocu lture in a reliable way. In our system it was however necessary to tra nsfer the embryos at Day 5 to coculture in Menezo-B2 medium to ensure optimal continuation of development.