Oestradiol concentration as a predictor of ovarian response in FSH stimulated ewe-lambs

We investigated the prediction of ovarian response using oestradiol determination, in 37 gonadotrophin stimulated Karagouniko ewe-lambs. Ovarian stimulation was induced by serial FSH administrations, and laparoscopic follicular aspiration (OPU) was conducted 12 h after the last FSH injection. Oestradiol concentration was assessed in six blood samples collected prior to each FSH injection and in one sample collected prior to follicular aspiration. According to ovarian response, ewe-lambs were allotted in three groups: good, L1 (n = 17); moderate, L2 (it = 10); and poor, L3 (n = 10). Based on the data obtained from 28 (75%) randomly selected animals, a statistical model was designed and tested on the remaining nine lambs for its ability to predict the probability of good ovarian response. From the 2nd sample, oestradiol concentration was constantly higher in group L I in comparison with L3 lambs (all p-values for the contrasts were <= 0.02), while this difference between L I and L2 lambs was significant only in the 6th and 7th sample (both p < 0.005). Using as criterion the oestradiol concentration of the 6th sample, the statistical model predicted all lambs that did not belong to group L1 and three of four lambs that belonged to group L1. Our results indicate that the moderate- and poor-donors could be safely predicted on the basis of oestradiol concentration 12 h prior to the scheduled follicular aspiration. Moreover, poor-donors could be identified-and rejected from further manipulations-on the basis of their inability to exhibit increased oestradiol levels in response to gonadotrophin stimulus. (c) 2007 Elsevier B.V. All rights reserved