The semen microbiome of miniature pony stallions.

Context: Little is known about the microbial composition of stallion semen.

Aims: To describe the microbiota detected in equine semen of healthy miniature pony stallions.

Methods: Semen specimens were collected using a Missouri artificial vagina at a single time point. PacBio (Pacific Biosciences) genomic DNA sequencing of the 16S rRNA gene was performed on these specimens, following which next-generation microbiome bioinformatics platform QIIME2 was used to process fastq files and analyse the amplicon data. The data were categorised into genus, family, class, order and phylum.

Key results: Firmicutes and Bacteroidetes phyla predominated (76%), followed by Proteobacteria (15%). Bacteroidales, Clostridiales and Cardiobacteriales predominated the microbial rank of order (86%). Class was mainly composed of Bacteroidia, Clostridia and Gammaproteobacteria (87%), while family was mainly composed of Porphyromonadaceae , Family_XI and Cardiobacteriaceae (62%). At the level of genus, 80% of the abundance was composed of seven genera, namely Porphyromonas, Suttonella, Peptoniphilus, Fastidiosipila, Ezakiella, Petrimonas and an unknown taxon.

Conclusions: The findings indicate that specific microbiota may be characteristic of healthy miniature pony stallions' semen with some inter-individual variations observed.

Implications: Larger equine studies involving fertile and infertile subjects could be informed by this study and could explore the relationship of the semen microbiome to male fertility.