Higher rates of development into blastocyst following the in vitro fertilization of bovine oocytes matured in a medium supplemented with the fluid from large bovine follicles

The effects of increasing amounts (0–60%) of bovine follicular fluid (bFF) from large follicles ( ≥ 15 mm in diameter) added to medium supplemented with 10% (v/v) oestrous cow serum (MSES) (TCM 199+LH+FSH+10% oestrous cow serum) on in vitro maturation of bovine follicular oocytes and on their subsequent development to the blastocyst and hatched blastocyst stages were investigated. After 24 h of incubation, the oocytes were fertilized and then cultured for 10 days. The effects of addition of oestrous cow serum (ECS) to maturation medium (at 15%) on development of the oocytes were also examined. Bovine follicular fluid had no stimulatory effect on the rate of nuclear maturation. However, supplementation of maturation medium with 10 or 15% bFF resulted in significantly higher proportions of morulae, blastocysts and hatched blastocysts. Although supplementation of maturation medium with ECS was also beneficial for development of bovine oocytes, probably, the interactions between the factors in bFF and ECS prevented achievement of an additive effect when both fluids were added at this concentration. In conclusion, the results suggest that the fluid from large bovine follicles contains stimulatory substance (s) that during in vitro maturation promotes the potential of bovine follicular oocytes for the subsequent development to blastocysts and hatched blastocysts.