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.

中文翻译：

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牛小母牛人工授精时的阴道细菌群落组成和雌二醇浓度。

围绕牛阴道微生物群的知识及其对生育能力和生殖性状的影响仍然不完整。本研究的目的是在人工授精（AI）时表征牛阴道细菌群落和雌二醇浓度。Brangus小母牛（n = 78）经历了7天的Co-Synch +控制性内部药物释放发情同步方案。在AI医院，使用双重保护子宫培养拭子对阴道前阴道取样。擦拭阴道后，立即通过尾静脉穿刺采血以测定雌二醇的浓度。小母牛回顾性地分为怀孕（n = 29）与未怀孕（n= 49）在AI后41至57天之间。此外，小母牛分为低（1.1至2.5 pg / mL；n = 21），中（2.6至6.7 pg / mL；n = 30）和高（7.2至17.6 pg / mL；n = 27）浓度。雌二醇 通过使用Illumina Miseq平台对来自16S rRNA基因的V4区域进行测序来确定阴道细菌群落组成。通过ANOVA比较Alpha多样性，通过PERMANOVA比较Beta多样性。Shannon多样性指数（α多样性；P = 0.336）或Bray-Curtis不相似性（β多样性；P= 0.744）的怀孕小母牛与未怀孕的小母牛。总体而言，雌激素含量高，中或低的小母牛的细菌群落组成没有差异（P = 0.512）。虽然未观察到总体组成差异，但怀孕状态和雌二醇浓度组之间存在物种水平差异。这些物种水平差异的含义尚不清楚，但这些差异可能会改变阴道环境，从而影响生育能力和阴道健康。因此，与动物生殖健康有关的物种水平的变化可能比整体微生物组成提供更好的见识。