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 competence 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 follicles (<5 mm) or e) medium follicles (5 to 10 mm) from untreated ovaries. Selected oocytes obtained from ovaries collected at the slaughterhouse were washed and matured in TCM-199 supplemented with 10% of the above bFF and/or 10% bovine estrous serum (BES) and gonadotropins (LH and FSH). The oocytes were then fertilized in vitro and cultured with oviductal vesicles for 6 d. The resulting ova (n=1793) were fixed and stained, and the number of nuclei was counted. The average number of nuclei 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 follicles than in bFF from superovulated animals, respectively. The overall proportion of ova reaching the >16-, >32-, >64- or >128-cell stage was similar for those matured in bFF and BES. The proportion of ova reaching the >16-cell stage was higher (P<0.04) for those matured in bFF from selected follicles (dominant or superovulated) than in bFF from pooled follicles. Among oocytes matured in the presence of pooled bFF, the proportion of those reaching the >16- (P<0.02) or the >32-cell stage (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 the 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 superovulated 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 competence.