Abstract
The objective of this study was to determine the association between circulating (Progesterone, oestradiol-17β and P4/E2 ratio) concentrations and embryonic loss in Friesian cows under Egyptian condition. On day 25 by both progesterone (P4) level and sonography, 65.71% (69/105) cows were continued their gestation normal and 17.14% (18/105) cows not conceived. While, 17.14% (18/105) of inseminated cows showed high P4 level firstly and decline before day 25 suspecting early pregnancy loss, EPL. Also, 5 cows (7.25%) of the pregnant cows lost their feti from day 25 to day 45 (late pregnancy loss, LPL) were detected. Progesterone concentrations was noticed that increased P4 level starting from day 4 to day 7after AI in cows diagnosed pregnant (P<0.05) compared to low P4 in cows lost pregnancy (8.03 & 8.98 ng/ml vs. 4.4 & 4.9 ng/ml respectively). Cows with LPL showed increasing P4 concentration in the first 25 days and got down on days 28 and 40 accompanied with embryonic loss. concentrations of estradiol were increased (P<0.05) significantly in cows with EPL starting from days 4 to 21 after AI compared to cows diagnosed pregnant. P4/E2 ratio was significantly (P<0.05) higher in cows diagnosed pregnant starting from days 4 to 40 after AI compared to cows loss their embryos early from days 4 to 25 after mating, while LPL cows has highest P4/E2 ratio during 25 days post AI and declined on days 28 to 40 in Friesian cows. It can concluded that the percentage of EPL was 17.14% and the percentage LPL was 7.25% during the 1st 45 days post mating in Friesian dairy cows raised in Sakha Experimental Station. Ultrasound is an excellent diagnostic imaging tool for detection of early embryonic losses.

Key words: Friesian cows, embryonic loss, progesterone and oestradiol-17β concentrations.