Primer oocytes (n=157) collected from ovaries of slaughtered cows were matured at 39°C with 95-100% humidity and under a gas mixture of 5% O 2 , 5% CO 2 and 90% N 2 for 22 (n=52), 24 (n=52) and 26 (n=53) hours. Modified Parker's Medium (MPM) supplemented with FSH and 20% ECS was used as maturation medium. At the end of these periods all oocytes were fixated in ethanol:acetic acid in the ratio of 3:1 for 24 hours and stained by %2 aceto-orcein to evaluate the maturational criteria. At the 22, 24 and 26-hours maturation groups, 23(%44.2), 27 (%51.9) and 30 (%56.6) oocytes reached the metaphase I and II stages, respectively. The difference among the groups was not important statistically (p>0.05).

Primer oocytes (n=157) collected from ovaries of slaughtered cows were matured at 39°C with 95-100% humidity and under a gas mixture of 5% O 2 , 5% CO 2 and 90% N 2 for 22 (n=52), 24 (n=52) and 26 (n=53) hours. Modified Parker's Medium (MPM) supplemented with FSH and 20% ECS was used as maturation medium. At the end of these periods all oocytes were fixated in ethanol:acetic acid in the ratio of 3:1 for 24 hours and stained by %2 aceto-orcein to evaluate the maturational criteria. At the 22, 24 and 26-hours maturation groups, 23(%44.2), 27 (%51.9) and 30 (%56.6) oocytes reached the metaphase I and II stages, respectively. The difference among the groups was not important statistically (p>0.05).