The semen microbiome of miniature pony stallions

The Equilibrium of Bacterial Microecosystem: Probiotics, Pathogenic Bacteria, and Natural Antimicrobial Substances in Semen

Semen is a complex fluid that contains spermatozoa and also functions as a dynamic bacterial microecosystem, comprising probiotics, pathogenic bacteria, and natural antimicrobial substances. Probiotic bacteria, such as Lactobacillus and Bifidobacterium, along with pathogenic bacteria like Pseudomonas aeruginosa and Escherichia coli, play significant roles in semen preservation and reproductive health. Studies have explored the impact of pathogenic bacteria on sperm quality, providing insights into the bacterial populations in mammalian semen and their influence on sperm function. These reviews highlight the delicate balance between beneficial and harmful bacteria, alongside the role of natural antimicrobial substances that help maintain this equilibrium. Moreover, we discuss the presence and roles of antimicrobial substances in semen, such as lysozyme, secretory leukocyte peptidase inhibitors, lactoferrin, and antimicrobial peptides, as well as emerging antibacterial substances like amyloid proteins. Understanding the interactions among probiotics, pathogens, and antimicrobial agents is crucial for elucidating semen preservation and fertility mechanisms. Additionally, the potential for adding probiotic bacteria with recombinant antibacterial properties presents a promising avenue for the development of new semen extenders. This review offers updated insights to understand the equilibrium of the bacterial microecosystem in semen and points toward innovative approaches for improving semen preservation.

16s gene metagenomic characterization in healthy stallion semen

Studies on the bacterial composition of seminal samples have primarily focused on species isolated from semen and their effects on fertility and reproductive health. Culture-independent techniques, such as 16S rRNA gene sequencing and shotgun metagenomics, have revolutionized our ability to identify unculturable bacteria, which comprise >90% of the microbiome. These techniques allow for comprehensive analysis of microbial communities in seminal samples, shedding light on their interactions and roles. In this study, we characterized the taxonomic diversity of seminal microbial communities in healthy stallions using 16S rRNA gene sequencing. Semen samples were collected from four stallions during the reproductive season, and DNA was extracted for sequencing. The results revealed a diverse array of bacterial taxa, with Firmicutes, Bacteroidota, and Proteobacteria being predominant phyla. At the family and genus levels, significant variations were observed among individuals, with individual variability in microbial richness and diversity standing out. Moreover, each stallion showed a distinct microbial fingerprint, indicating the presence of a characteristic microbial core for each stallion. These results underscore the importance of considering individual microbial profiles in understanding reproductive health and fertility outcomes.

Effect of probiotics and prebiotics on the composition of the equine fecal and seminal microbiomes and sperm quality: A pilot study

Probiotic and prebiotic effects on equine semen and gastrointestinal microbiome composition and sperm quality are unknown. This study aimed to evaluate the effects of pre-, pro- or synbiotic supplementation on fecal and semen microbiome composition and sperm quality parameters of stallions. This Latin square crossover trial involved four miniature pony stallions receiving control diet only, or addition of a pro-, pre- or synbiotic formulation. Full-length 16S rRNA gene amplicon sequencing was used to measure diversity of semen and fecal microbiomes. Total sperm count, total motility, progressive motility, DNA integrity, lipid peroxidation and mitochondrial oxidative stress, biomarkers of sperm quality, were measured after each intervention. A general linear model was employed to analyse and compare microbiome diversity measures and sperm quality data across four time points. Shannon's diversity index (alpha-diversity), and evenness of semen and gastrointestinal microbiomes were significantly different (p<0.001). A trend was observed for prebiotic effects on the diversity indices of the GI microbiome (p= 0.07). No effects of treatments were observed on either semen microbiome or sperm quality. Pre-, pro- and synbiotic supplements showed no negative effect on sperm quality parameters observed. This proof of concept provides preliminary data to inform future studies exploring the relationship between microbiomes and fertility.