Evaluation of freeze-dried bull spermatozoa by intra-or inter-species micro insemination

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The purpose of this study was to investigate whether freeze-drying process of bull spermatozoa disturbed early post-fertilization events essential to gain the developmental competence of intracytoplasmically sperm-injected(ICSI) oocytes. In interspecies assay using mouse ovulated oocytes, the ability of freeze-dried(FD) bull spermatozoa to induce normal intracellular calcium oscillation pattern was comparable despite of temperatures stored for 1 year. DNA fragmentation in FD spermatozoa stored at+ 4℃was not detected by alkaline comet assay. With intraspecies(bovine-bovine) ICSI, the FD process was found to be innocent in performance of epigenetic remodeling(active DNA demethylation) and function of microtubule-organizing center(sperm aster formation and network assembly) in the pronuclear-stage zygotes. Factors responsible for low blastocyst yield from the FD-ICSI bovine oocytes remain to be determined.