Semester of Graduation

Summer 2024


Master of Science (MS)


Veterinary Clinical Sciences

Document Type



The equine lower reproductive tract harbors bacterial populations that serve as a reservoir for potential pathogens. Dysbiosis of urogenital sites may play a role in reproductive disease of the mare, including endometritis. Metagenetic studies have evaluated microbiomes in the uterus, vagina and placenta, while the clitoral microbiome has yet to be described. In this study, the following hypotheses were tested; 1) the clitoris harbors a unique microbiome, 2) topical Lactobacillus genus complex (LGC) probiotic will alter this microbiome, 3) acceptable per cycle pregnancy rates (PCPR) following probiotic application will be achieved. Reproductively normal mares (n=14) were selected, and clitoral fossa samples were collected immediately prior (0h) to topical once daily application of a silicone-based gel containing Lactiplantibacillus pentosus YUN-V1.0 and Lactiplantibacillus plantarum YUN-V2.0 (dose: 109 CFU/gram) for 4 days. Samples were then collected 12 (12h) and 48 (48h) hours after completion of treatment. On the following estrus cycle, mares were bred by artificial insemination with one billion progressively motile spermatozoa. Genomic DNA extraction and quality control were performed prior to multiplex sequencing of the V4 region using an Illumina Miseq platform for 12 subjects (2 excluded due to insufficient reads). The 3 most abundant phyla in the clitoral microbiome were Firmicutes, Bacteroidota, and Fusobacteriota. Dominant taxa of the clitoris reflected greater similarities to previous reports of vaginal, compared with endometrial, microbiomes. Alpha diversity measures were not significantly different between timepoints. Significant differences in beta diversity were shown between 0h and 12h (P=0.005) and 0h to 48h (P=0.003) via PERMANOVA with false discovery rate adjustment. When changes in relative abundance of top 10 phyla and top 25 genera were evaluated via Friedman test with pairwise Dunn’s post hoc comparisons, significant differences (PLactobacillus was increased (P= 0.003) in the clitoral fossa at 12h, then returned to baseline levels by 48h. An acceptable PCPR (85%) was achieved when mares were bred on the following estrus. These results suggest the equine clitoris harbors a unique microbiome which was dynamically altered following LGC probiotic application, with no interference on normal fertility parameters.



Committee Chair

Sones, Jenny L.

Available for download on Tuesday, April 15, 2025