The semen microbiome of miniature pony stallions

Little is known about the microbial composition of stallion semen.

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

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.

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.

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

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.