105 Morphokinetic profiling of in vitro-produced bovine embryos in relationship with oocyte donor’s health status during the transition period

This study aimed to analyse the effect of oocyte donors’ health status on the developmental potential of in vitro-produced bovine embryos. In 30 multiparous Holstein cows, ovum pickup was performed twice weekly from the fifth to the eighth week postpartum, and collected oocytes underwent standard IVM, IVF, and in vitro culture. A total of 254 presumptive zygotes (PZ) were monitored until Day 9 with a time-lapse monitoring system (PrimoVision, Vitrolife), and the following morphokinetic parameters were recorded: the time of first (t1) and second cleavage (t2), the last cleavage before entering the lag-phase (t3), the cleavage resumption after the lag phase (tRCl), the start of blastocyst expansion (tSB), the start of hatching (tHB), and the end of hatching (tHDB). Cows were retrospectively assigned to one of the following groups: healthy (CON, n = 6), metabolic disorders (META, β-hydroxybutyrate acid > 1.2 mmol/L, n = 8), inflammatory disease (INF, somatic cell count > 200,000 cells/mL and/or vaginal discharge, n = 8) or combined disease (COMB, concurrence of metabolic and inflammatory diseases, n = 8). The effect of the disease group on the probability of in vitro-produced embryos to advance in their developmental stage was evaluated by a Cox proportional-hazards regression model. The regression coefficients b and the respective P-values were computed for each transition. Out of 254 PZ, 191 cleaved, and a total of 144 embryos developed to the blastocyst stage (blastocyst rate: 29/46 or 63%, 42/82 or 51%, 39/66 or 59%, and 34/60 or 56% for the CON, META, INF, and COMB groups, respectively). INF embryos were less likely to achieve stage t2 and t3 than CON embryos (b = −0.433, b = −0.117, respectively; P < 0.05). In contrast, INF embryos were more likely to reach tSB and tHB than CON embryos (b = 0.389 and b = 0.677, respectively; P < 0.05). META embryos showed higher chances to move from stage tSB to tHB than CON embryos (b = 0.236; P < 0.05). In addition, embryos of the COMB group showed higher chances to move from stages t1, t3, and tRCl to the respective subsequent stages than CON embryos (b = 0.387, b = 0.504, and b = 0.334, respectively: P < 0.05). However, META and COMB embryos showed a reduced potential to develop from tHB to tHDB than CON embryos (b = −0.763 and b = −0.805, respectively; P < 0.05). Herein, we showed the differential developmental potential of in vitro-produced embryos in relationship with the health status of the oocyte donor. Our results suggest that although embryos from cows with periparturient diseases displayed an overall higher developmental potential between the t3 and the tSB stages, META and COMB diseases negatively affect the hatching likelihood of in vitro-produced embryos and shed light on their possible negative effect on embryo implantation.