Epidermal growth factor enhances meiotic resumption of canine oocytes in the presence of BSA

Despite many attempts to improve the in vitro maturation (IVM) of canine oocytes using various culture conditions, the efficiency of canine IVM remains very low compared with that of other domestic animals. In the present study we examined the effect of ovarian estrus stage on oocyte quality, and the effect of epidermal growth factor (EGF) in the presence and absence of macromolecules on the IVM of canine oocytes. More oocytes ≥100 μm in diameter were obtained from follicular ovaries than from ovaries at other estrus stages. After 72 h of culture, significantly more oocytes recovered from follicular ovaries than from anestrous and luteal ovaries were in germinal vesicle break down (GVBD). Bovine serum albumin (BSA) or fetal bovine serum (FBS) supplementation improved meiotic resumption as compared to polyvinyl alcohol (PVA) supplementation; however, there was no difference between the BSA and FBS supplements. The oocytes matured in North Carolina State University (NCSU) 37 medium containing 0.4% BSA and 100 ng/ml EGF showed the highest rates of development to the metaphase II (MII) stage when compared with the control treatment (P < 0.05). These results suggest that the estrous cycle of bitches influences the meiotic resumption of oocytes cultured in vitro, and EGF increases the meiotic resumption of canine oocytes in the presence of BSA in vitro.