87 Bacterial communities of the uterus and vagina between resulting pregnant and non-pregnant postpartum beef cows

The prevalence of reproductive losses costing 1 billion dollars annually to the beef and dairy industries has led researchers to evaluate strategies to improve reproductive efficiency. The microbiome of the reproductive tract has been a recent focus in humans due to its effects on health and fertility; however, little research has evaluated the uterine and vaginal microbiomes of cattle. The present study evaluated the reproductive tract bacterial communities of postpartum beef cows undergoing estrus synchronization and the differences between cows who became pregnant and those who failed to conceive. Forty postpartum Angus cows were subjected to a 7 Day Co-Synch protocol with a pre-synchronization step 21 days prior (day -21) to artificial insemination (AI). Uterine and vaginal flushes were collected on day -21, -9, and -2 of the protocol for pH and bacterial DNA extraction to sequence the V1-V3 hypervariable regions of the 16S rRNA gene. Transrectal ultrasound was performed 30 days after AI for pregnancy diagnosis. Ten pregnant and non-pregnant animals were selected and used for analysis. Decreased numbers of bacterial species present in the uterus of cows were identified, independent of pregnancy status, leading up to AI with an average of 1180 ± 97 species on day -21 to 427 ± 99 on day -2 (P < 0.0001). Principal coordinate analyses depicted significant clustering of bacterial communities by day in the uterus (P = 0.001) and vagina (P = 0.001) as well as pregnancy status in the uterus at day -2 (P = 0.005). Additionally, at day -2, multiple significantly different uterine bacterial genera were present at >1% in non-pregnant cows while present at <1% in pregnant cows. Uterine pH increased in non-pregnant cows but decreased in pregnant cows. In summary, the results suggest uterine bacterial abundances prior to AI may influence the uterine environment and reproductive outcomes.