Composition and diversity of the preputial microbiota in healthy bulls

Characterization of microbial communities inhabiting the reproductive tracts of cattle may lead to a better comprehension of bovine physiology and reproductive health. To date, reported studies have utilized culture-independent 16S ribosomal RNA (rRNA) for the classification of microbiota in the vaginal tract of cows but no studies have looked at the microbiota of the prepuce or penis of the bull. The aim of this study was to elucidate the microbiota present on the epithelial surface of the penis and prepuce of the post-pubertal bull using 16S rRNA gene sequencing. Ninety-two healthy bulls of a variety of ages and breeding history, presented for routine breeding soundness examinations, were utilized in this investigation. Bacteria belonging to Firmicutes, Fusobacteria, Bacteroidetes, Proteobacteria, and Actinobacteria were identified in the prepuce. From all the bulls, two major community types were found, those with low or high bacterial species richness (up to 400 operational taxonomic units in one sample). There was no animal characteristic (breed or age) or management practice (feed type, antibiotic use, co-housing, breeding history) that was correlated with the bull penile microbial community composition. However, Bradyrhizobium was a distinguishing genus only found in the low diversity samples. The bull penile microbial community includes members of genera that are common in soil, cow vagina, respiratory tract, and feces. The baseline preputial microbial community in healthy bulls is described in the current study. This knowledge can be used later when investigating the interactions between disease and the male urogenital tract microbial community.