262 - Reproductive Microbiomes as Predicators of Fertility in Beef Cattle

Over the past decade, a multitude of research has sought to understand the complexity and role of the reproductive microbiome as it pertains to fertility. Previously, the reproductive microbiome was evaluated using culture-dependent methods; however, recent advancements in culture-independent, 16S rRNA gene amplicon community sequencing have vastly expanded our understanding of the reproductive tract microbiome. Early sequencing studies sought to compare the vaginal microbiome of cattle to the vaginal microbiome of healthy women, which predominantly consists of bacteria in the genus Lactobacillus and believed to be an indicator of fertility. In the vagina of beef cattle, however, there are incredibly low abundances of Lactobacillus and a greater diversity of bacterial species present. Beta-diversity, which examine differences in bacterial communities between samples, does not appear to differ in the vagina between unbred, open, or pregnant cattle. In postpartum beef cattle just prior to breeding, there are greater levels of diversity and increased bacterial species richness in the vagina compared to the uterus. Research on bacterial species within the uterus have primarily focused on pathogenic bacteria in postpartum cattle diagnosed with uterine disease. Fewer studies have investigated uterine bacterial species in presumed healthy postpartum beef cattle and the subsequent effects on fertility outcomes (e.g., pregnant vs. open at day 30). When evaluating the uterine microbiome during an industry standard estrus synchronization protocol, bacterial community abundance and diversity reduce over time regardless of resulting fertility outcomes. The greatest difference in uterine bacterial abundance between resulting pregnant and non-pregnant cattle appears to occur just prior to breeding. Numerous mechanisms could be contributing to the fluctuations in the uterine microbiome in beef cattle including circulating hormone concentrations or local immunoregulation. This presentation will focus on recent research investigating potential mechanisms that may alter the reproductive microbiome and ultimately impact fertility.