273effect of epidermal growth factor (egf) during oocyte maturation on in vitro production of bovine embryos

Medium components during in vitro maturation (IVM) can significantly influence oocyte maturation and subsequent embryo development in vitro (Rose TA and Bavister BD 1992 Mol. Reprod. Dev. 31, 72–77; Harper K and Brackett B 1993 Biol. Reprod. 48, 409–416). The aim of this experiment was to evaluate the effect of EGF during IVM on further development of bovine embryos in vitro. Bovine ovaries were obtained at a slaughterhouse. Cumulus-oocyte complexes (COC) were aspirated from follicles 2–5mm in diameter. COC were incubated for 24h in either of 3 maturation media: T1 (n=72): modified TCM-199; T2 (n=45): modified TCM-199 supplemented with 10ngmL−1 of EGF;; or T3 (n=46): modified TCM-199 supplemented with 10% fetal bovine serum (FBS). After 24h of IVM, COC were inseminated with 2×106 motile spermatozoa/ml. After 18h of gamete coincubation, presumptive zygotes were denuded and placed in culture in SOF rich in glutamine (g-SOf) for 72h, at which time, cleavage rate (%) wass assesed (embryos with >4 cells). Subsequently, cleaved embryos were incubated for an additional 72h in c-SOF (SOF rich in citrate and glucose). Finally, embryos were cultured in modified TCM-199 for 24–48h, at which time blastocyst formation rate (%) was evaluated. Cleavage rates were similar between T2 and T3 but significantly greater than in T1 (P>0.05; see Table 1). Addition of EGF during IVM (T2;; 11/45, 24.4%) did not yield more blastocysts compared to the other two treatments (6/57, 10.5% and 10/29, 34.5%, T1 and T3, respectively). Nonetheless, T3 (with serum) had a greater yield of blastocysts compared to T1 (P>0.01). Results in this study show that the addition of EGF to chemically defined media results in similar cleavage rates and blastocyst yields to those obtained when using serum during IVM. Key words: in vitro maturation, EGF, cleavage, bovine, embryo. Table 1 Effect of EGF and serum during IVM on cleavage rate of bovine oocytes