The effect of bovine follicular fluid from 2-5mm follicles and its fractions on maturation and subsequent fertilizability and cleavage of the oocytes in vitro

Abstract

In this study the bovine follicular fluid (bFF) from small follicles (2-5mm in diameter) or its fractions were added to maturation medium, and their effects on maturation, fertilization and cleavage of bovine follicular oocytes were examined. Oocytes from slaughtered Holstein cows were cultured in maturation medium supplemented with various concentrations of bFF or its fractions. After 22-24 hr of culture, the oocytes were coincubated with frozen-thawed spermatozoa, then cultured in development medium for 48 hr and at the end of culture evaluated for cleavage, nuclear maturation and fertilization. The bFF at 30% significantly enhanced maturation compared to bFF-free group (control); it also significantly enhanced cleavage beyond the 2-cell stage compared to bFF-free and 60% low molecular fraction (<10KD) groups. The 60% bFF group significantly enhanced fertilization compared to bFF-free group. In addition, the embryos derived from oocytes matured in the 60% bFF significantly proceeded to >2-cell stages. The fractions of bFF were without significant effect on the rates of maturation, fertlization or cleavage, except at 60% where the high molecular fraction (>10KD) significantly enhanced cleavage to 2-cells compared to bFF-free group, but the rates of embryos that cleaved beyond the 2-cell stage was significantly lower (P<0. 01) than in the 60% bFF group. In conclusion, addition of whole bFF (2-5mm follicles) to maturation medium was beneficial for maturation, fertilization and cleavage beyond the 2-cell stage of bovine oocytes at 30% and 60% concentrations. On the other hand, the fractions of bFF did not show significant effect on the rates of maturation and fertlization.