EFFECTS OF BOVINE FOLLICULAR-FLUID ON MATURATION OF BOVINE OOCYTES

Three experiments were conducted to determine the effects of follicula r fluid and media on bovine oocyte maturation. Experiments 1 and 3 tes t the effects of follicular fluid obtained at different times after th e LH surge on bovine oocyte maturation in vitro, while Experiment 2 wa s designed to compare TALP and Medium 199 as serum-free maturation med ia. Bovine follicular fluid (BFF) was obtained from preovulatory folli cles either before (0 h BFF) or at 4, 8, 12 or 20 h after a GnRH-induc ed LH surge. Oocytes were obtained from follicles 1 to 6 mm in diamete r from ovaries retrieved from a slaughterhouse. In Experiment 1, both 0 h and 4 h BFF inhibited resumption of meiosis, whereas BFF collected at 8, 12 and 20 h did not. When oocytes were cultured in media that c ontained equal portions of 0 and 8 h BFF, meiosis was not inhibited. I n Experiment 2, Medium 199 supplemented with bovine serum albumin (BSA ) was superior to Tyrode's medium with albumin, lactate and pyruvate f or oocyte maturation. In Experiment 3, a higher percentage (P<0.05) of oocytes cultured for 18 h in 40% 20 h BFF in Medium 199 reached Metap hase-II (64%) than those cultured in 0 h BFF (41%) or control medium ( 39%). There was a transient meiotic arrest due to 0 h BFF as evidenced by the higher percentage of oocytes with germinal vesicles at 8 h of incubation (35% with 0 h vs 20% with 20 h; P<0.05). Furthermore, expan sion of cumulus cells was induced in 8 and 20 h BFF, but not 0 h BFF.