THE ASSESSMENT OF FOLLICULAR PARAMETERS FOR THE SELECTION OF OOCYTES RECOVERED FROM SUPEROVULATED HEIFERS

Superovulated mature Holstein heifers were ovariectomized at the expected time of ovulation in order to recover preovulatory follicles. Follicular fluid steroid concentrations from all follicles 8 mm and greater in diameter were determined and correlated with oocyte morphology and the luteinizing hormone (LH) surge in the oocyte donor. Of the 11 oocyte donors used in this study, two did not exhibit a surge (-LH). Fluid from the aspirated follicles ranged from 0.1 to 1.4 ml in volume. Overall, 79 oocytes were recovered from 127 aspirated follicles. Heifers exhibiting an LH surge (+ LH) produced follicles with a significantly higher oocyte recovery rate (P<0.0001). Follicular fluid volume was not a significant predictor of oocyte recovery success (P<0.40). Using accepted morphological criteria for oocyte classification, the 79 recovered oocytes were classified as 40 mature, 22 degenerate, 3 immature, 13 bare and 1 not classified. Follicular fluid steroid data were available for 39 mature oocytes, of which 38 were from +LH heifers, and 21 degenerate oocytes, of which 11 were derived from +LH animals. While mature and degenerate oocytes were obtained from follicles exhibiting a range of fluid volumes and steroid concentrations, mature oocytes were more commonly derived from follicles with progesterone concentrations of greater than 100 ng/ml, estradiol concentrations of 5-60 ng/ml, testosterone concentrations of 5-45 ng/ml and a fluid volume of at least 0.3 ml (10 mm diameter). © 1990.