Vaginal Microbiota Is Stable throughout the Estrous Cycle in Arabian Maress.
Authors: Barba Marta, Martínez-Boví Rebeca, Quereda Juan José, Mocé María Lorena, Plaza-Dávila María, Jiménez-Trigos Estrella, Gómez-Martín Ángel, González-Torres Pedro, Carbonetto Belén, García-Roselló Empar
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Vaginal Microbiota Stability across the Equine Estrous Cycle Contrary to patterns observed in other mammals, the vaginal microbiota of Arabian mares remains remarkably stable throughout the estrous cycle, according to research combining both culture-dependent and molecular sequencing methods. Eight healthy mares were sampled during oestrus and dioestrus, with bacterial identification performed via traditional culturing on selective media and 16S rRNA gene sequencing (Illumina MiSeq); notably, lactic acid bacteria comprised less than 1% of the community regardless of cycle phase, with Lactobacillus alone accounting for only 0.18–0.37%. The core equine vaginal microbiome was dominated by anaerobic and facultative anaerobes—primarily Porphyromonas, Campylobacter, Arcanobacterium, Corynebacterium and Fusobacterium—with no significant shifts in microbial composition or diversity between reproductive phases. These findings suggest that unlike humans and some other mammals where oestrogen-driven changes shape the vaginal bacterial landscape, equine reproductive hormone fluctuations do not substantially alter the resident microbial community structure. For practitioners managing mare fertility, this stability implies that reproductive-tract health strategies should focus on maintaining the established microbiota rather than expecting or relying upon cyclical microbial remodelling, and that diagnostic interpretation of vaginal cultures requires understanding this distinct equine-specific microbiological profile.
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Practical Takeaways
- •Unlike humans, equine vaginal microbiota is not LAB-dominated and does not fluctuate with estrous cycling, suggesting different mechanisms of pathogen control in mares
- •Vaginal microbiota stability throughout the estrous cycle indicates that reproductive tract infections in mares are not primarily driven by microbiota shifts related to ovarian hormone changes
- •Clinicians should not expect significant microbiota composition changes when collecting samples from mares at different cycle stages for diagnostic purposes
Key Findings
- •Lactic acid bacteria comprised only 2% of total bacterial isolates in Arabian mares and showed no relationship to ovarian phase
- •Vaginal microbiota diversity and composition remained stable between estrus and diestrus phases
- •Core equine vaginal microbiome consists of Firmicutes, Bacteroidetes, Proteobacteria and Actinobacteria with Porphyromonas, Campylobacter, and Arcanobacterium as dominant genera
- •Lactobacillus abundance was minimal (0.18% in estrus, 0.37% in diestrus) with no significant differences between cycle phases