173 IN VITRO EMBRYO PRODUCTION FROM OOCYTES FERTILISED WITH UNSORTED OR X-SORTED SPERM AND ISSUED FROM SUBFERTILE HIGH GENETIC MERIT COWS SUBMITTED OR NOT TO A 48-h COASTING PERIOD FOLLOWING FSH STIMULATION

High genetic merit cows may be sidelined from breeding schemes because of reproductive disorders. In vitro production of embryos (IVP) issued from ovum pickup (OPU) can be an alternative to bypass infertility problems as experienced in humans and thus accelerate genetic progress (Duszewska et al. 2012 J. Anim. Feed Sci. 21, 217–233). The aim of this work was to evaluate if IVP from high genetic merit subfertile cows could benefit to the breeding scheme under commercial conditions, at the Biotechnology MIDATEST Station located in Denguin, Southwest, France. Holstein cows (n = 16) from 3.5 to 13 years old with different reproductive pathologic problems (repeated breeding, failure in in vivo embryo production, embryo mortality, permanent cysts, oviduct infection) were used in an OPU-IVP program. Donor cows were stimulated with decreasing doses pFSH twice daily during 3 days (Stimufol®, total dose: 350 µg of pFSH). The OPU was performed 48 h after the last FSH injection in the “coasting” group v. 12 h after the last FSH injection for “no-coasting” group and in vitro matured using a standard IVM protocol. Oocytes were fertilised with frozen-thawed unsorted or X-sorted sperm in TALP medium from different bulls (n = 42) without any previous IVP testing. Presumptive zygotes were cultured in SOF medium (Minitub®) plus 1% cow serum up to Day 7 at 38.5°C in 5% CO2, 5% O2, and 90% N2 atmosphere with maximum humidity. The OPU-IVP was repeated 1 to 6 times (3.75 ± 2.6) for each donor cow. Grade 1 blastocysts and expanded blastocysts (according to IETS classification) were recorded on Days 6.5 and 7. Embryo production was analysed with ANOVA and blastocyst yield was analysed by chi-square. The results in both coasting or no-coasting groups and the effect of fertilization using unsorted or X-sorted sperm are presented in Table 1. The embryonic development rate was significantly higher when using unsorted semen to fertilize the oocytes compared to X-sorted sperm (P < 0.05). On the other hand the coasting period had no significant effect neither on the number of collected oocytes nor on the embryonic development rates. In conclusion, our work confirmed the efficacy of OPU-IVP techniques to produce grade 1 embryos using X-sorted or unsorted sperm in subfertile high genetic merit cows. Table 1.Oocyte collection and in vitro embryo production, in donor cows submitted or not to a 48-h coasting period and effect of fertilization with unsorted v. X-sorted sperm