Bacterial communities from vagina of dairy healthy heifers and cows with impaired reproductive performance.

Vaginal microenvironment plays a significant role in bovine fertility since its resident microorganisms interact with the host mucosa and constitutes the first barrier against ascending pathogens in the reproductive tract. In this study, the vaginal microbiome of healthy heifers (H) and cows with impaired reproductive performance, metritis complex (MT) or repeat breeders (RB), was assessed using a 16S rRNA gene sequencing approach. Analysis revealed that even though a vaginal microbiological guild (Firmicutes, Bacteroidetes, Proteobacteria, Tenericutes, Fusobacteria and Actinobacteria) was shared among healthy heifers and cows with uterine disease; further analysis at genus level showed significant differences depending on the reproductive health status. The relative abundances of recognized uterine pathogens such as Bacteroidetes, Fusobacterium and Helcococcus were higher in MT when compared with H and RB; therefore, their presence in vagina can be considered as a risk factor for fertility. The present study describes for the first time, the composition of native bacterial communities in the vagina of cows undergoing the repeat breeding syndrome (RBS), and reports an association between this disease and the presence of Porphyromonas and unassigned genera of the Pasteurellaceae family. In addition, this work highlights the bacteria associated with a healthy vagina: genera from the families Lachnospiraceae, Rikenellaceae and the genera Acinetobacter, Bacillus, Oscillospira, CF231 and 5-7NS. Results highlighted herein, signify the potential of the evaluation of the bovine vaginal microbiome to future design therapeutic interventions to improve pregnancy rates however, further research is needed to elucidate the balance of bacterial species resulting in an optimal reproductive health.