Vaginal bacterial community composition and concentrations of estradiol at the time of artificial insemination in Brangus heifers

Authors: MESSMAN, RILEY - Mississippi State University; CONTRERAS-CORREA, ZULLY - South Dakota State University; PAZ, HENRY - South Dakota State University; PERRY, GEORGE - South Dakota State University; LEMLEY, CALEB - Mississippi State University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2020
Publication Date: 5/26/2020
Citation: Messman, R., Contreras-Correa, Z., Paz, H., Perry, G., Lemley, C. 2020. Vaginal bacterial community composition and concentrations of estradiol at the time of artificial insemination in Brangus heifers. Journal of Animal Science. 98(6):1-9.

Interpretive Summary: The role and importance of the vaginal microbiota in fertility and reproduction have been recently explored in sheep, cattle, horses, and humans. In general, the vaginal microbiota is dynamic and constantly changing in the aforementioned species. Research in cattle analyzing the vaginal microbiome is limited. Specifically, there is a significant lack of research evaluating the vaginal microbiome’s role in bovine fertility and how the microbiome could be influenced by reproductive hormones. Therefore, we characterized the vaginal microbiota in relation to pregnancy status and circulating concentrations of estrogen in Brangus heifers. In conclusion, no differences were found in the vaginal bacterial community profiles of heifers with different pregnancy status or estrogen concentrations. Overall, it can be concluded that the vaginal microbiome is diverse and finding significant differences in the composition as a whole has proven difficult.

Technical Abstract: The knowledge surrounding the bovine vaginal microbiota and its implications on fertility and reproductive traits remains incomplete. The objective of the current study was to characterize the bovine vaginal bacterial community and estradiol concentrations at the time of artificial insemination (AI). Brangus heifers (n = 78) underwent a 7-d Co-Synch + controlled internal drug release estrus synchronization protocol. At AI, a double-guarded uterine culture swab was used to sample the anterior vaginal tract. Immediately after swabbing the vaginal tract, blood samples were collected by coccygeal venipuncture to determine concentrations of estradiol. Heifers were retrospectively classified as pregnant (n = 29) vs. nonpregnant (n = 49) between 41 and 57 d post-AI. Additionally, heifers were classified into low (1.1 to 2.5 pg/mL; n = 21), medium (2.6 to 6.7 pg/mL; n = 30), and high (7.2 to 17.6 pg/mL; n = 27) concentration of estradiol. The vaginal bacterial community composition was determined through sequencing of the V4 region from the 16S rRNA gene using the Illumina Miseq platform. Alpha diversity was compared via ANOVA and beta diversity was compared via PERMANOVA. There were no differences in the Shannon diversity index (alpha diversity; P = 0.336) or Bray–Curtis dissimilarity (beta diversity; P = 0.744) of pregnant vs. nonpregnant heifers. Overall, bacterial community composition in heifers with high, medium, or low concentrations of estradiol did not differ (P = 0.512). While no overall compositional differences were observed, species-level differences were present within pregnancy status and estradiol concentration groups. The implications of these species-level differences are unknown, but these differences could alter the vaginal environment thereby influencing fertility and vaginal health. Therefore, species-level changes could provide better insight rather than overall microbial composition in relation to an animal’s reproductive health.