PSI-18 - Vaginal microbiome of Bos indicus cattle in relation to fertility

Abstract: Shifts in commensal bacteria (e.g., Firmicutes) in the human vaginal microbiome are associated with compromised fertility. The objective of this study was to characterize the reproductive microbiome in the vagina of Bos indicus females prior to fixed-timed artificial insemination (FTAI). Bos indicus females on operations within a 20-mile radius (RANCH 1, RANCH 2, RANCH 3, RANCH 4) were subjected to the 7-day CO-Synch + CIDR protocol on day (d)-9 and FTAI on d0. Sterile vaginal swabs were collected on d-9 (CIDR IN), d-2 (CIDR OUT), and d0 (AI). Cattle were body condition scored (BCS) on d0. Pregnancy status was determined by transrectal ultrasonography (Non-pregnant, n=44 and Pregnant, n=34). Bacterial community analyses were conducted targeting the V4 hypervariable region of the 16S rRNA gene. Data were analyzed using PROC GLM in SAS 9.4. Body condition scores did not significantly differ by pregnancy status or ranch. Additionally, there was no difference in bacterial relative abundance between pregnant or non-pregnant (P > 0.10). The vaginal relative abundance of Firmicutes differed between CIDR IN, CIDR OUT, and AI days (63.54% vs. 28.11% vs. 60.66% ± 1.96%; P < 0.0001). Pregnancy rate did differ by ranch (RANCH 1 63.6% ± 14.7%, RANCH 2 60.0% ± 10.9%, RANCH 3 28.0% ± 9.7%, RANCH 4 36.4% ± 10.4%; P = 0.074). There was a difference observed between ranches with RANCH 4 having the greatest relative abundance of Firmicutes and RANCH 1 having the lowest (58.84% ± 2.12% vs. 45.12% ± 3.17%; P = 0.0001). A tendency for increased relative abundance of Firmicutes was noted in cows compared to heifers (53.03% ± 1.71% vs. 48.51% ± 1.89%; P = 0.099). Under the phylum of Firmicutes, the genera of Ruminococcus, Clostridium, Blautia, Butyrivibrio, and Mogibacterium followed a similar trend with a shift in relative abundance between CIDR IN, CIDR OUT, and AI days (Table 1). RANCH 1 had the lowest relative abundance of Ruminococcus and Clostridium and the greatest relative abundance of Blautia compared to other ranches (P < 0.05). A shift in relative abundance between CIDR IN, CIDR OUT, and AI days was observed for the phylum of Proteobacteria (7.84% vs. 26.44% vs. 9.69% ± 1.82%; P < 0.0001) and Bacteroidetes (12.19% ± vs. 15.62% vs. 12.67% ± 1.07%; P = 0.046). A tendency for differences in the relative abundance of Bacteroidetes between ranch were observed with RANCH 2 having the greatest relative abundance and RANCH 3 having the lowest (15.36% ± 1.29% vs. 11.73% ± 1.21%, respectively; P = 0.066). These results suggest a distinct difference in the vaginal microbiome prior to FTAI. In addition, microbial relative abundances within the vagina also differ between ranches of similar genetics and region.