Levels of plasma steroid hormones in relation to retained fetal membrane (RFM) in dairy cows

The levels of plasma progesterone (P4), 17β-estradiol (17β-E2), and estrone (E1) were measured by RIA in twenty pregnant cows (10 RFM and 10 NRFM cows). Jugular vein blood samples were collected from 10 days before parturition until 2 days after parturition. The results indicated that level of plasma progesterone in RFM cows was slight lower at the 6th-3rd days pre-partum than in NRFM cows (P>0.05), increased abruptly at 2nd day of pre-partum and was significantly higher than that of NRFM cows (P<0.05). The level of plasma 17β-estradiol in RFM cows was significantly lower than that of NRFM cows (P<0.05) at the day of pre-partum until the day of parturition, in particular at the 7th day and 5th day of pre-partum. The level of plasma estrone was significantly lower in RFM cows at the 10th-1st days of pre-partum than that in NRFM cows (P<0.05). At the 8th and 4th day, it was significantly lower than that of NRFM cows (P<0.01) and was significantly higher at the day of parturition than that of NRFM cows (P<0.05). In addition, P4/17β-E2 ratios in RFM cows at 6th and 2nd day of pre-partum were significantly high. The results show that the significant decrease of estrone level and significant increase of P4/17β-E2 ratios at the 6th day of pre-partum may be reliable indicators of retained placenta in dairy cows