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Individual bull variations on sperm acrosome reaction, sperm-zona binding, in-vitro embryo production, and preimplantation embryo apoptosis and gene expression

University of British Columbia

The overall objective of this study was to develop in-vitro tests to predict fertility of bulls in the field. The specific objectives were to investigate 1) the bull effect on sperm acrosome reaction, sperm-zona binding and in vitro embryo production (experiment 1), 2) the effect of sperm pre-incubation time and sperm concentration of bulls on in-vitro fertilization (experiment 2), 3) the bull effect on apoptosis and expression of Bcl-2, Bax, p53, interferon tau and heat shock protein-70 genes in bovine preimplantation embryos produced in-vitro (experiment 3), and 4) the correlation between the above in-vitro tests and the field fertility data. In the first experiment, prefreeze motility, acrosome reaction at 0 h, increase in acrosome reaction at 4 h and sperm-zona binding were different (p<0.05) among bulls. Significant correlations were observed between individual sperm parameters. None of the in-vitro tests was correlated with non-return rates (field fertility data). In the second experiment, significant bull effects were observed on fertilization, when using short and long sperm pre-incubation time with normal and high sperm:oocyte ratio. When using normal sperm:oocyte ratio (25,000:1), the percent difference in normally fertilized zygotes between short and long sperm pre-incubation times showed high degree of correlation with non-return rates (r = 0.90; p<0.05) of the experimental bulls. In the third experiment, significant bull effects (P<0.01) were observed on cleavage and morula to blastocyst development rates; percentage of apoptotic, live and dead cells; and expression levels of heat shock protein 70 and interferon tau genes in morula to blastocyst stage embryos. The expression levels of Bax, Bcl-2 and p53 genes in morula to blastocyst stage embryos were not different among bulls. The field fertility measured by 60-90 day non-return rate was highly correlated with relative abundance of Bcl-2 mRNA transcripts (r = -0.93) and the ratio of Bax to Bcl-2 gene expression (r = 0.84). The findings of this study conclude that variations exist among individual bulls in sperm acrosome reaction, sperm-zona binding and in-vitro embryo production, apoptosis, and interferon tau and heat shock protein 70 gene expression. Combinations of some of these sperm parameters may be potentially useful for the accurate prediction of bull fertility in the field.

Thesis/Dissertation

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2009-12-02

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http://hdl.handle.net/2429/16157

Animal Science

University of British Columbia

UBCV

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