[Four years of ovum pick-up (OPU) and in vitro fertilization (IVF) in Belgian blue donor cows]

Between 1996 and 2000 79 Belgian blue donor cows were submitted to OPU-IVF. They all had a history in classical embryo transfer programs with disappointing results. Two different in vitro embryo production protocols were used. Between 1996 and 1998 (period A), oocytes were matured in M 199 and Epidermal Growth Factor (EGF) and Foetal Calf Serum (FCS) were added. Subsequently, the, oocytes were cultured in a granulosa co-culture system in a Synthetic Oviduct Fluid (SOF) medium. From 1998 until 2000 (Period B), M 199, FCS, equine chorionic gonatrophin (eCG) and granulosa cell co-culture were used for in vitro maturation. Zygotes were subsequently cultured in SOF with a co-culture of bovine oviduct epithelial cells (BOEC). During period A, 531 OPU-IVF sessions were performed, collecting 2111 cumulus oocyte complexes (COCs), of which 928 (44%) were of good morphological quality. The in vitro maturation (IVM), fertilization (IVF) and culture (lVC) resulted in 241 transferable embryos. When fresh embryos (n=88) were transferred, a pregnancy rate of 27% was obtained, whereas the transfer of frozen embryos (n=18) resulted in 29% pregnant recipients. During period B, 1519 OPU sessions were performed, collecting 7027 COCs, with 2157 (31%) of them being of good quality. Following IVM-IVF-IVC, we cultured 1120 transferable embryos of which 438 were transferred fresh, resulting in a pregnancy rate of 39%. The transfer of frozen embryos (n=139) yielded a pregnancy rate of only 5%. The overall results improved over the years, while individual donor variability was one of the main factors that had influence on the OPU-IVF success rate. At the end of the second period, an average of 0.8 embryos were obtained per OPU session. Since freezing of in vitro derived bovine embryos is still problematic, the transfer of fresh embryos remains the best option. However, in our circumstances the availability of good quality recipients appeared to be the limiting factor.