Effect of epidermal growth factor (EGF) and defined simple media on in vitro bovine oocyte maturation and early embryonic development

The purpose of this study is to evaluate the effect of EGF and defined simple media on in vitro bovine oocyte maturation and early embryonic development. Bovine follicular oocytes were matured in vitro and co-cultured with frozen-thawed bull sperm, which was capacitated with Hepes buffered saline (HBS) solution. After incubation of oocyte-sperm complexes for 4 days, the cleavage rate was evaluated. The results obtained were as follows: 1) When bovine oocytes were matured and embryos were developed in Park-Lin medium 1 (PL(1)) containing fetal calf serum (FCS) or EGF + bovine serum albumin (BSA), the latter treatment was more effective in inducing embryonic cleavage (18%) than FCS alone (10%). 2) When bovine oocytes were matured in Park-Lin medium 2 (PL(2)) without EGF and the subsequent embryos were developed in PL(2) medium with EGF, the cleavage rate was 22.6%. 3) When bovine oocytes were matured in PL(2) medium with EGF and then the embryos were developed in PL(2) medium with EGF, the cleavage rate was 35.8%. 4) When bovine oocytes were matured in Park-Lin medium 3 (PL(3)) without EGF and then the embryos were developed in PL(3) medium, the cleavage rate was 50%. 5) When bovine oocytes and resulting embryos were matured in PL(3) medium with EGF, the cleavage rate was 53%. 6) The parthenogenesis rate induced by PL(3) medium in our current study was comparable to the findings reported by other laboratories. These results suggest that EGF stimulates in vitro bovine oocyte maturation and subsequently affects embryonic development. It is suggested that PL(3) medium is a better defined simple medium than the other media currently used by other laboratories for in vitro bovine oocyte maturation.