Maturation timing and fetal bovine serum concentration for developmental potential of sheep oocytes in vitro

The success of in vitro embryo production (IVEP) in animals has improved over time, employing a variety of culture media. Here, we assessed the maturation timing and developmental potential of sheep oocytes in vitro at different concentrations of fetal bovine serum (FBS): Cumulus oocyte complexes (COCs) were aspirated from follicles (2-6 mm) of sheep ovaries collected from local slaughter house. COCs were randomly divided into two groups and matured at 38.5'C, 5% CO2 for 24 h (Group I) and 27 h (Group II). Oocytes cultured for 27 h showed significantly (P <0.05) more maturation than those cultured for 24 h (82 vs. 76%) followed by more cleavage (35 vs. 30%), morula (53 vs. 39%) and blastocyst (17 vs. 11%) percentage. In the second experiment, oocytes were randomly divided into two groups and matured with 10% FBS (Group I) and 20% FBS (Group II) for 27 h supplemented with pyruvate, glutamine, LH, FSH and estradiol. After maturation, oocytes were fertilized by fresh semen for 18 h. Presumptive zygotes in both the groups were again divided into two groups and culturedin 10 and 20% FBS during post fertilization period, respectively. Different FBS concentration in maturation medium did not influence maturation percentage (82 vs. 79%) significantly. Out of culture groups, presumptive zygotes matured in 20% FBS and cultured in 20% FBS during post fertilization period showed significant increase in cleavage percentage (44 vs. 39, 35 and 27%) as compared to other groups but subsequent development to morula (55 vs. 53, 43 and 40%) and blastocyst (20 vs. 17, 16 and 15%) percentage were more in the group matured in 10% FBS and cultured in 20% FBS during post fertilization period.