Effect of probiotics and prebiotics on the composition of the equine fecal and seminal microbiomes and sperm quality: A pilot study.
Authors: Cooke C Giselle, Gibb Zamira, Grupen Christopher G, Schemann Kathrin, Deshpande Nandan, Harnett Joanna E
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Probiotics, Prebiotics and Equine Stallion Fertility The equine breeding industry lacks evidence on whether dietary microbiome-modulating supplements influence reproductive function, prompting researchers to investigate how probiotic, prebiotic and synbiotic formulations affect both gastrointestinal and semen microbiota alongside conventional sperm quality markers in four miniature pony stallions across a Latin square crossover design. Using full-length 16S rRNA sequencing and validated assessments of sperm motility, DNA integrity, lipid peroxidation and mitochondrial oxidative stress, the team identified significant treatment-dependent shifts in both fecal and seminal microbial diversity (Shannon's diversity index; p<0.001), with prebiotic supplementation showing a trend towards enhancing gastrointestinal microbiome diversity (p=0.07). Critically, none of the three supplement types produced measurable improvements in conventional sperm quality parameters—total count, progressive motility or oxidative stress markers all remained unaffected—though reassuringly, no adverse effects were documented either. Whilst this pilot study's small sample size and miniature pony population limit direct extrapolation to full-sized performance stallions, the findings suggest that targeting the microbiome alone may not yield immediate reproductive benefits through mechanisms captured by standard semen analysis, indicating that future investigations should examine longer intervention periods, diverse horse breeds and whether microbiome composition correlates with in-vivo fertility outcomes rather than laboratory sperm metrics.
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Practical Takeaways
- •Pro-, pre-, and synbiotic supplements appear safe for stallions and do not compromise sperm quality, supporting their use if gastrointestinal health benefits are sought
- •Current evidence does not support microbiome supplementation as a strategy to improve stallion fertility or sperm parameters in clinical practice
- •Larger, longer-duration studies are needed before recommending these supplements specifically for enhancing reproductive performance
Key Findings
- •Shannon's diversity index and evenness of semen and gastrointestinal microbiomes were significantly different across treatments (p<0.001)
- •A trend toward prebiotic effects on GI microbiome diversity indices was observed (p=0.07)
- •No significant effects of pro-, pre-, or synbiotic supplementation were observed on semen microbiome composition or sperm quality parameters
- •No negative effects on sperm quality parameters were detected with any supplement tested