Seasonal Fluctuation of Estrogen, Progesterone, Vaginal pH, and Cervical Morphology in Arabian Mares under Natural Photoperiod
DOI:
https://doi.org/10.48165/ijapm.2026.42.1.11Keywords:
seasonality, estrogen, progesterone, vaginal pH, vaginoscopy, cervixAbstract
Seasonality modulates reproductive endocrine activity and the genital tract microenvironment in mares, with marked inter-individual variation in the depth of winter suppression. This study evaluated seasonal variation in estrogen, progesterone, vaginal pH, and cervix appearance assessed by vaginoscopy in Arabian mares under natural photoperiod in Baghdad, Iraq. Ten healthy mares aged between 5 to 15 years (9±3 years) were examined for one year and categorized as true polyestrus mares (Group A; n = 6) or seasonal polyestrus mares with winter anestrus (Group B; n = 4). Blood samples were collected at 15-day intervals (10 days in irregular cycles) and analyzed for estrogen and progesterone using commercial equine ELISA kits. Vaginoscopy and vaginal pH measurement were performed on Day 1 of the follicular phase and Day 15 of the luteal phase. Group A mares exhibited relatively stable hormone profiles across the seasons, while Group B mares showed a significant decline of estrogen and progesterone hormones during the winter season, coordinated with deep anestrus. Vaginoscopy revealed cervical changes: during estrus the cervix was relaxed, open, and moist, red color, clear mucosa, and dilation typically resting on the vaginal floor, whereas during diestrus it appeared pale, dry, tightly closed and elevated; during anestrus the cervix tended to be pale, dry and drooped on the vaginal floor. Seasonal mares also showed a significant winter acidification of vaginal pH, due to seasonal modulation of the vaginal microenvironment.References
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