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The aime of this study was to assess the effects of different concentrations of fetal calf serum and estrous sheep serum on in vitro maturation of ovine oocytes. Ovine ovaries were isolated from a local slaughter house and transported to the laboratory. Oocytes were aspirated from the folicles and washed 4 times in TCM-199 with or without different concentrations (10, 15 and 20%) of heat inactivated fetal calf serum (FCS) or estrous sheep serum (ESS), and cultured in TCM-199 under paraffin oil. After 24 h culture for maturation, oocytes were denuded from cumulus cells and were mounted on slide glass, fixed, stained and observed under a phase contrast microscope for evidence of maturation, Very few oocytes were matured in the medium without each serum. However maturation rates were significantly increased (P<0.001) when the media were supplemented with sera. The results of the present study shows that the maturation in ESS medium is comparable to
FCS.