Short- and long-term effects of uterine disease on oocyte developmental capacity in postpartum dairy cows.

The hypothesis was that early postpartum uterine disease would reduce the developmental capacity of oocytes thus contributing to the reduced fertility of dairy cows with uterine disease. Dairy cows were diagnosed healthy or with metritis at 7 to 10 d postpartum. The reproductive tract was collected at approximately 1 mo (Exp. 1) or approximately 80 or 165 d (Exp. 2) postpartum for the collection of cumulus-oocyte complexes (COC). The COC were matured, co- incubated with sperm for fertilization, and cultured to the blastocyst stage (8 d) in vitro. For Exp.1, the disease diagnosis (healthy or metritis) did not affect the number of collected COC or the subsequent embryo development to the blastocyst stage. The presence of purulent material in the uterine lumen (endometritis) at time of oocyte collection, however, was associated with a reduced cleavage rate evaluated 3 d following fertilization. For Exp. 2, there was no effect of disease diagnosis (healthy or metritis) on the number of COC or their subsequent development. Reduced cleavage rates were observed in COC retrieved from cows slaughtered at 80 d postpartum, but not at 165 d postpartum, and this reduction was associated with a vaginal microbiome indicative of uterine disease at 4 to 5 wk postpartum. Regression analyses that included plasma haptoglobin or energy metabolite concentrations or uterine bacterial genera abundance did not explain a large percentage of the variation in oocyte development in vitro. We conclude that there is an effect of uterine disease at one month postpartum on the oocyte and its capacity for development (Exp. 1) and this effect may be present at 80 d postpartum (Exp. 2). In later postpartum cows (165 d postpartum; Exp. 2) there was no effect of uterine disease on in vitro oocyte development. GRAPHICAL ABSTRACT: HIGHLIGHTS: Oocytes collected at 1 month postpartum from dairy cows with endometritis (purulent uterine lumen) had a lower cleavage rate following in vitro fertilization when compared with oocytes collected from healthy cows (Exp. 1).Oocytes collected at approximately 80 d postpartum from dairy cows with evidence of uterine disease at 4 to 5 wk postpartum had a lower cleavage rate following in vitro fertilization but this disease-associated difference was not observed when oocytes were collected from cows later postpartum (approximately 165 d postpartum; Exp. 2).Regardless of the study (Exp. 1 or 2), uterine disease primarily affected the percentage of oocytes that cleaved after fertilization.Statistical associations between circulating metabolites or relative abundance of uterine bacteria were either not significant or explained only a small percentage of the variation in the in vitro embryo development in either experiment.