186 Examining the Vaginal Microbiome During Gilt Reproductive Development

Abstract

Abstract Gilt reproductive failure is a common challenge in the US swine industry. Indeed, as many as three million breeding females are removed from swine herds each year, resulting in an annual replacement rate of 40%. Furthermore, about 20% of gilts selected for replacement never successfully enter the reproductive herd. The vaginal microbiome may play a role in gilt reproductive success; this study compared the vaginal bacterial composition from eight gilts at two pre-pubertal time points (d70 and d130 of age). Vaginal swabs were collected and analyzed using the 16S rRNA gene through PCR-amplification of the V1-V3 regions from vaginal microbial genomic DNA, followed by Illumina MiSeq 2X300 sequencing. Seven of the gilts achieved first estrus between d 164 and d 190 days of age based on physical signs of vulva swelling and locked stance in the presence of a boar. One female had no visible signs of estrus before 210 d of age. Beta diversity analysis by PCoA revealed that samples clustered into two separate groups according to time points. Alpha diversity indices (Sobs, Ace and Chao) were numerically decreased between d 70 to d 130. A comparative analysis of the most highly represented Operational Taxonomic Units (OTUs) using the non-parametric Kruskal-Wallis sum-rank test and Wilcoxon pairwise test identified 12 OTUs that varied in abundance (P < 0.05) between the two time points. Notably, OTU SD_Ssd-00001, predicted to be a strain of Lactobacillus amylovorus (99.82% sequence identity), was greatest at d 70 (21.33%), then significantly decreased at d 130 (7.67%). In contrast, OTU SD_Ssd-01393, corresponding to an uncultured species of Prevotellaceae (closest relative: Prevotella disiens, 92.48%), was in less abundance at d 70 (4.87%), but became the most abundant OTU at d 130 (18.19%). The vaginal OTUs identified in this study included not only known bacterial species, such as members of the Lactobacillus genus which have been previously found to be normal and beneficial residents of the human vagina, but also uncharacterized bacterial species. These results are indicative of distinct vaginal microbiome composition between d 70 and d 130 of age and suggest that certain bacterial species could potentially be used as indicators of reproductive potential in gilts.