The aim of study was to know the pro le of progesterone in milk samples of dairy cows that experienced after pregnancy failure AI. Milk samples of fteen AI failure dairy cows were taken on days 0, 7, 14, 21 and 28 (day 0 = estrus). Progesterone analysis was performed by ELISA method. On day 7th and 14thprogesterone concentrations has increased in all cows, on 21th day the levels were decreased in 3 cows and they returned to estrous, while in 12 cows the progesterone levels were high
