Determination of optimal dose of EGF for bovine oocyte maturation and subsequent in vitro fertilization and culture in two media
The aim of this study was to determine the optimal dose of EGF on in vitro maturation of bovine oocytes and to investigate the effect of different IVF and IVC media on development of bovine embryos matured with EGF. Oocytes collected from a slaughterhouse were randomly divided into 4 groups. Each group of oocytes was incubated with different doses of EGF (Control: 0 ng/mL, Group 1: 1 ng/mL, Group 2: 10 ng/mL, and Group 3: 100 ng/mL) for 24 h to determine the optimal dose. Matured oocytes were fertilized with frozen-thawed bull sperm by using the swim-up method. The oocytes in each group were divided into 2 subgroups and cultured in CR1aa or G1.3/G2.3 media. Embryos were evaluated for cleavage (48th h), and 5-8 cell embryo (day 3) and blastocyst development (day 8) after fertilization. The rates of cumulus expansion and nuclear maturation were higher (P < 0.01) in GI, GII, and GIII compared to the control group. However, no significant difference was observed on oocyte maturation rates between different doses of EGF. Cleavage rates were higher (P < 0.01) in EGF groups than in the control group. No significant differences were obtained in blastocyst development between CR1aa and G1.3/G2.3 media (P > 0.1).
Key words: Bovine, oocyte, EGF, maturation, in vitro culture