Effects of acrosomal conditions of frozen-thawed spermatozoa on the results of artificial insemination in Japanese Black cattle

The purposes of this study were to examine the relationship between male artificial insemination (AI)fertility and sperm acrosomal conditions assessed by new and conventional staining techniques and to identifypossible reproductive dysfunctions causing low conception rates in AI using frozen-thawed spermatozoa withpoor acrosomal conditions in Japanese Black bulls. We investigated individual differences among bulls in theresults concerning (1) acrosomal conditions of frozen-thawed spermatozoa as assessed by not merely peanutagglutinin-lectin staining (a conventional staining technique) but also immunostaining of acrosomaltyrosine-phosphorylated proteins (a new staining technique), (2) routine AI using frozen-thawed spermatozoa asassessed by pregnancy diagnosis, (3) in vivo fertilization of frozen-thawed spermatozoa andearly development of fertilized eggs as assessed by superovulation/AI-embryo collection tests and (4)in vitro fertilization of frozen-thawed spermatozoa with oocytes. The percentages offrozen-thawed spermatozoa with normal acrosomal conditions assessed by the abovementioned staining techniqueswere significantly correlated with the conception rates of routine AI, rates of transferable embryos insuperovulation/AI-embryo collection tests and in vitro fertilization rates. These results areconsistent with new suggestions that the distribution of acrosomal tyrosine-phosphorylated proteins as well asthe acrosomal morphology of frozen-thawed spermatozoa are AI fertility-associated markers that are valid forthe prediction of AI results and that low conception rates in AI using frozen-thawed spermatozoa with pooracrosomal conditions result from reproductive dysfunctions in the processes between sperm insemination intofemales and early embryo development, probably failed fertilization of frozen-thawed spermatozoa withoocytes.