Progesterone concentration as an indicator of ovarian response to superovulation in Chios ewes

We investigated the prediction of the ovarian response to superovulation using progesterone (P-4) determination in Chios ewes. During the estrus period, estrus synchronization and multiple ovulations were induced in 100 non-pregnant, non-lactating Chios ewes by a combination of FGA-impregnated intravaginal sponges and 8.8 mg of ovine FSH, Laparoscopic insemination was conducted 24-28 h after the onset of estrus. A concentration Of P4 was determined on Day 5 of the estrous cycle and on Day 6 the ovarian response was evaluated by counting the corpus lutea (CL) subsequently, embryo collection was performed, According to the response of their ovaries, ewes were allocated into four groups: A (n = 30), B (n = 37): C (n = 22) D (n = 11). with minimal (0-3 CL), moderate (4-8 CL), good (9-13 CL) or extreme (>13 CL) ovarian response, respectively. In groups C and D, the mean blood serum P-4 concentration (23.2 and 27.3 ng/ml, respectively) was higher (P < 0.001) than that in groups A and B (4.6 and 13.1 ng/ml, respectively); no difference was detected in blood P-4 concentration between groups C and D. A strong linear relation (F < 0.00005) was found between blood P-4 concentration and the number of CL, as well as between blood P4 and a dummy variable corresponding to poor (<4 CL) or moderate/good/extreme ovarian response (>3 CL). Our results indicate that based on blood P-4 measurement, it is feasible to identify ewes that should show the highest embryo recovery, while it is impossible to predict the exact number of CL formed. (C) 2002 Elsevier Science Inc. All rights reserved.