''In vitro'' maturation of bovine oocytes of Nelore breed.

The aim of this investigation was to assess the viability of the ''in vitro'' maturation oocytes of Nelore breed. This study utilized Nelore and crossbreed Holstein x Zebu oocytes, obtained from ovaries at a slaughterhouse. The oocytes were aspirated from follicles with a 3ml seringe, and washed in Talp Hepes medium at 37 degrees C. All oocytes surrounded by cumulus cells were selected, washed again in Talp Hepes medium and cultured in TCM 199 medium with 10% estrus cow serum, 20mcg/ml FSH, 5% CO2 air, in co-culture of granulosa cells at 39 degrees C, for 24h. After ''in vitro'' maturation, the oocytes were fixed, stained and evaluated for nuclear maturation. The maturation rate for Nelore and cross breeding Holstein x Zebu oocytes were, respectively, 76.27% (n=118) and 86.53% (n=104). This difference was not significant, showing the viability of these oocytes during the ''in vitro'' maturation process.