RESUMEN
Zearalenone (Zen) and its metabolites are estrogenic and may be important factors involved in reproductive disorders in domestic animals. We aimed to (1) simultaneously detect Zen and its metabolites in bovine follicular fluids (FFs) by liquid chromatography-tandem mass spectrometry and (2) examine the in vitro effects of Zen on bovine oocytes. Zen and its metabolites were detected in 6 of 32 normal follicles and 7 of 20 cystic follicles. Bovine oocytes were cultured in a maturation media containing various Zen concentrations (0 [control], 1, 10, 100, and 1000microg/L), fertilized, and cultured further. Maturation rates decreased dose-dependently. Further, maturation of 62 (50%) of 124 oocytes examined in the 1000-microg/L group was arrested in metaphase I, without affecting the fertilization rate. Blastocyst-formation rates did not significantly differ among the groups. Zen and its metabolites were detectable in bovine FFs. High Zen concentration may adversely affect meiotic competence but not the fertilization and development rates.