Effect of LH-RH on meiotic maturation of preovulatory oocytes in superovulated heifers

Abstract Eleven heifers (Group 1) were stimulated for 4 days by 20 mg of FSH-P administered in declining doses. Cloprostenol (0.75 mg) was administered 48 h after the first FSH-P dose. Eight heifers (Group 2) were stimulated according to the same patterns, but 40 h after the injection of cloprostenol they were treated with 50 μg of LH-RH analog. The onset of the LH peak was observed 35.9 ± 1.26 and 40.2 ± 0.03 h after the administration of cloprostenol in Groups 1 and 2 respectively ( P P > 0.05). The LH concentration was 11.1 ± 3.49 ng ml −1 in Group 1 and 58.5 ± 5.05 ng ml −1 in Group 2 ( P P P P P > 0.05), and 25.9% and 40.0% had released the first polar body ( P P