ORIGIN OF THE FOLLICULAR-FLUID ADDED TO THE MEDIA DURING BOVINE-IVM INFLUENCES EMBRYONIC-DEVELOPMENT

The objectives of this study were to evaluate the developmental compet ence of bovine oocytes matured in the presence of selected follicular fluids (bFF) harvested a) from large follicles of FSH-treated cows on the fourth day of FSH treatment; b) from dominant follicles during the growing or c) the regressing phase; and d) from a pool of small folli cles (<5 mm) or e) medium follicles (5 to 10 mm) from untreated ovarie s. Selected oocytes obtained from ovaries collected at the slaughterho use were washed and matured in TCM-199 supplemented with 10% of the ab ove bFF and/or 10% bovine estrous serum (BES) and gonadotropins (LH an d FSH). The oocytes were then fertilized in vitro and cultured with ov iductal vesicles for 6 d. The resulting ova (n=1793) were fixed and st ained, and the number of nuclei was counted. The average number of nuc lei per ovum at the >16-cell (P<0.07) and the >32-cell stage (P<0.05) was higher for those matured in the presence of bFF from dominant foll icles than in bFF from superovulated animals, respectively. The overal l proportion of ova reaching the >16-, >32-, >64- or >128-cell stage w as similar for those matured in bFF and BES. The proportion of ova rea ching the >16-cell stage was higher (P<0.04) for those matured in bFF from selected follicles (dominant or superovulated) than in bFF from p ooled follicles. Among oocytes matured in the presence of pooled bFF, the proportion of those reaching the >16- (P<0.02) or the >32-cell sta ge (P<0.06) was lower for those matured in a pool of medium follicles than the pool of small follicles. The proportion of embryos reaching t he 64-cell stage was higher (P<0.04) for those matured in the presence of bFF from dominant follicles than in the presence of bFF from super ovulated animals. Based on the evaluation of the number of nuclei per embryo, it is concluded that the origin of follicular fluid influences the ability of in vitro-matured oocytes to acquire developmental comp etence.