Ovarian synchronization by follicle aspiration and moderate FSH treatment improves oocyte quality and the efficiency of in vitro embryo production in cattle

Oocytes obtained by ovum pick-up (OPU) from cows are heterogeneous with regard to chromatin compaction, and those with an intermediate degree have higher developmental competence. We have developed a protocol combining follicle aspiration and FSH treatment that increases the percentage of oocytes with intermediate chromatin compaction at OPU. In this study, we assessed the effect of this protocol on in vitro embryo production following OPU. Eighteen non-lactating Holstein cows had all follicles larger than 3mm aspirated and a progesterone intravaginal device inserted on a random day (day 0). Four IM injections of FSH (Folltropin; 40/40/20/20mg) were administered 12h apart on days 2 and 3. On day 5, the progesterone device was removed and OPU was performed. The control group consisted of seventeen non-lactating Holstein cows submitted to OPU on a random day. After OPU, cumulus-oocyte complexes (COC) underwent in vitro maturation (IVM) for 24h in a medium containing 0.5 mg/mL FSH and 10% bovine fetal serum, followed by in vitro fertilization and in vitro (IVC) culture of the presumptive zygotes. After seven days of IVC, embryo production was assessed to determine the percentage of blastocysts in relation to the number of oocytes subjected to IVM, and percentage of viable embryos (morphologically selected for freezing and later transfer) in relation to total blastocysts. Data were arcsine transformed and groups compared with the Student’s t test. Blastocyst rate was higher in the treatment group (37.91 ± 6.48%; 79/206) in relation to the control (20.98 ± 2.62%; 78/348; P<0.05). Control and treatment groups did not differ for percentage of viable embryos (65.19 ± 8% and 64.89 ± 11.18%, respectively). These data indicate that protocols combining antral follicle removal and FSH treatment to homogenize the oocytes population for IVM can improve the efficiency of embryo in vitro production in cattle. Supported by FAPESP 2016/21671-9.