Fertilization in vitro of bovine oocytes after various sperm procedures

Fertilization in vitro of bovine follicular oocytes cultured in vitro was attempted after various procedures on frozen-thawed bull spermatozoa. The frozen-thawed semen was diluted at 1 : 15 and treated with one of eight methods as follows: 1) no washing, 2) washing, 3) passing through a glass wool column, 4) washing and bovine follicular fluid (BFF), 5) Ham's F-12 based medium and BFF (1 : 1), 6) BFF only, 7) a high ionic strength (HIS) treatment and the medium, or 8) HIS treatment and BFF. A total of 766 oocytes was examined for the identification of fertilization (the presence of the pronuclei and a sperm midpiece in the oocyte cytoplasm and the second polar body) and cleavage at 24 h after insemination. The sperm procedures by BFF treatment with or without washing showed significantly higher rates of fertilization (P<0.05) than the other methods tested, except after HIS treatment. The highest fertilization rate (46.2%) was obtained by the treatment with BFF only. The results indicate that BFF could favorably affect capacitation of frozen-thawed bull spermatozoa and its subsequent fertilization in vitro.