The aim of this study was to assess the effect of oocyte selection using the brilliant cresyl blue (BCB) test plus the addition of cysteamine to the in vitro maturation (IVM) medium to improve the in vitro embryo development of prepubertal goat oocytes. The oocytes were exposed to 26 µM BCB and classified according to their cytoplasm coloration: BCB+ (oocytes with blue cytoplasm) and BCB-(unstained oocytes). The oocytes were matured in a conventional IVM medium supplemented with cysteamine 100

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... M. The control group consisted of oocytes not exposed to BCB and matured without cysteamine. The IVM-oocytes were inseminated and cultured in synthetic oviductal fluid (SOF) for 7 days. The normal fertilisation rate (oocytes showing 2 pronuclei and 1 sperm tail) of BCB+ oocytes (40%) was higher than those of BCB-(21%) and control oocytes (22%). The percentage of morulae plus blastocysts was higher (P < 0.05) in the BCB+ group than in the BCB-group (23.8 vs. 5.1%, respectively). In conclusion, the integration of the BCB test and the addition of cysteamine in the protocol of in vitro embryo production from prepubertal goat oocytes has improved the developmental rates of embryo development. embryo / IVF / IVM / thiol Reprod. Nutr. Dev. 43 (2003) 179-187 179