Changes in fecal microbiota during estrous cycle in healthy thoroughbred mares.
Authors: Li Junjie, Toyama Haruka, Matsumoto Touko, Qasimi Mohammad Ibrahim, Inoue Ryo, Murase Harutaka, Yamamoto Yuki, Nagaoka Kentaro
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Fecal Microbiota Changes During the Equine Estrous Cycle Whilst the gut microbiota's role in reproduction is well established in humans and rodents, evidence in mares remained limited; this Japanese research team therefore examined whether cyclical fluctuations in oestradiol-17β and progesterone correlate with shifts in faecal microbial composition across the normal oestrous cycle. Five healthy thoroughbred mares underwent sequential blood and faecal sampling throughout their cycles, with serum hormones quantified via radioimmunoassay and microbial communities profiled using 16S rRNA gene sequencing. The major microbial taxa and overall richness remained remarkably stable throughout follicular and luteal phases; however, Linear Discriminant Analysis identified the Rhodococcus genus as significantly more abundant during specific cycle phases, suggesting this low-abundance taxon responds to hormonal fluctuations even when the dominant microbiota architecture does not. These findings suggest that whilst gross dysbiosis does not accompany normal reproductive cycling in mares, subtle shifts in minor bacterial populations—particularly potential pathogens like Rhodococcus—warrant attention, particularly in mares experiencing subfertility or reproductive disease where such dysbiosis might be pathogenic rather than physiological. For practitioners managing mares' performance and fertility, this work implies that cycle-related microbiotic changes are unlikely to require preemptive probiotic or dietary intervention in healthy animals, though individual variation and disease states may alter this picture.
Read the full abstract on PubMed
Practical Takeaways
- •Mare gut microbiota composition is generally stable across the estrous cycle, suggesting estrous-related behavioral changes are not driven by major microbiome shifts
- •Specific pathogenic bacteria (including Rhodococcus) fluctuate with reproductive hormones; consider monitoring in mares with recurrent infections or digestive issues during specific cycle phases
- •Estrous cycle phase may influence susceptibility to certain bacterial infections—timing of antimicrobial therapy or probiotic supplementation could potentially be optimized based on cycle stage
Key Findings
- •Overall richness and composition of gut microbiota remained relatively stable throughout the normal estrous cycle in mares
- •Rhodococcus genus identified as differentially abundant between follicular and luteal phases via Linear Discriminant Analysis Effect Size analysis
- •Low-abundance pathogenic bacteria showed changes aligned with fluctuations in estradiol-17β and progesterone levels
- •Significant microbial composition consistency observed despite cyclic steroid sex hormone variations