Melatonin-induced changes in the bovine vaginal microbiota during maternal nutrient restriction

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

Submitted to: Journal of Animal Science Supplement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2021
Publication Date: 5/18/2021
Citation: Messman, R.D., Contreras-Correa, Z.E., Paz, H.A., Lemley, C.O. 2021. Melatonin-induced changes in the bovine vaginal microbiota during maternal nutrient restriction. Journal of Animal Science Supplement. 99, 5, 1-10. https://doi.org/10.1093/jas/skab098.
DOI: https://doi.org/10.1093/jas/skab098

Interpretive Summary: Despite decades of research, much remains to be elucidated in reproductive physiology. Specifically, questions surrounding infertility, conception, fetal programming, and reproductive tract health remain unanswered. In cattle, the role of the reproductive tract microbiota has not been widely studied. Therefore, a major gap in knowledge exists in reproductive performance, an important economic trait in cattle production. Researchers in the Animal and Dairy Science Department are characterizing the vaginal microbiota in cattle during significant reproductive milestones. Vaginal swabs were collected to identify and compare the microbiota present. The vaginal microbiota was compared between pregnant and nonpregnant heifers, from breeding to mid-gestation, and across the compromised pregnancy groups. Researchers hypothesized that compositional differences would be observed in all comparisons. The current research impacts the reproductive scientific community by addressing a knowledge gap in the literature regarding the role and impacts of the vaginal microbiota. These studies provide direction for future analysis suggesting that species level changes could have major impacts in the reproductive tract microbiota. Moreover, changes were observed in pregnant versus nonpregnant heifers and the therapeutic supplement, melatonin altered the diversity of vaginal microbiota during late gestation, specifically decreasing the abundance of anaerobic bacteria. This research is fundamental to uncovering the role of the bovine vaginal microbiota in reproductive performance.

Technical Abstract: Altering the composition of the bovine vaginal microbiota has proved challenging, with recent studies deeming the microbiota dynamic due to few overall changes being found. Therefore, the objectives of this study were to determine if gestational age, endogenous progesterone, maternal nutrient restriction, or dietary melatonin altered the composition of the bovine vaginal microbiota. Brangus heifers (n = 29) from timed artificial insemination to day 240 of gestation were used; at day 160 of gestation, heifers were assigned to either an adequate (ADQ; n = 14; 100% NRC requirements) or restricted (RES; n = 15; 60% NRC requirements) nutritional plane and were either supplemented with dietary melatonin (MEL; n = 15) or not supplemented (CON; n = 14). Samples for vaginal microbiota analysis were taken on day 0 (prior to artificial insemination), day 150 (prior to dietary treatments), and day 220 of gestation (60 days post-treatment initiation) using a double guarded culture swab. The vaginal bacterial overall community structure was determined through sequencing the V4 region of the 16S rRNA gene using the Illumina Miseq platform. Alpha diversity was compared via two-way ANOVA; beta diversity was compared via PERMANOVA. The linear discriminant analysis for effect size (LEfSe) pipeline was utilized for analysis of taxonomic rank differences between bacterial communities. Gestational age, progesterone concentration, and maternal nutritional plane did not alter alpha or beta diversity of the vaginal microbiota. However, gestational age resulted in compositional changes at the order, family, and genus level. Moreover, dietary melatonin supplementation did not alter alpha diversity of the vaginal microbiota but did alter beta diversity (P = 0.02). Specifically, melatonin altered the composition at the genus level and increased the prevalence of aerobic bacteria in the vaginal tract. To date, melatonin is the first hormone associated with altering the composition of the bovine vaginal microbiota.