Plasma steroid evaluations are well established approaches for monitoring reproductive function in mares. The purpose of this study was to detect the first ovulation time by the estimation of progesterone and estradiol-17β profiles in plasma samples of Azerbaijan Arabian brood mares. Eight seasonally an ovulatory light horse mares were selected from Tabriz horse stable and blood samples were obtained every week for progesterone and estrogen determination. Chemiluninescence immunoassay was used as the method for progesterone and estrogen concentration measuring. After six weeks sampling (start from 12Th of January), in seventh week (23Th of February), estradiol-17β concentration had a significant increasing (P‹0.0001). One week later progesterone concentration increased too (P‹0.0001). In conclusion, both p4 and E1-17β in plasma analysis have a predictive value for assessment of ovulation time in brood mares and the first ovulation time in Azerbaijan brood mares start from beginning of the march.
