Abstract
The effects of culture time for oocyte maturation and the injection conditions of capacitated sperm (with/without manipulation medium) on the subsequent morphological changes in male and female nuclei and the development of embryos derived from microfertilization of bovine oocytes were investigated. The rates of cleavage and development to blastocyst stage increased with the extension of maturation time of oocytes from 18h to 25h.
The best results (2-cell: 71.4%, blastocysts: 11.4%) were obtained from the oocytes cultured for 25 h. Microinjection of sperm into the oocytes without manipulation medium, resulted in higher (P<0.05) developmental rates (2-cell: 28.8%, blastocysts: 9.6%) than those (19.5% and 4.9%) from sperm with manipulation medium. This result suggested that the injected manipulation medium was harmful to the ooplasm and affected the development of embryos. The development of embryos derived from microfertilization up to 3-to 7-cell stage and over 8-cell stage was delayed for 4 h and 8 h than those from in-vitro morphological observation of the male and female nuclei after the microinjection, the formation of male pronucleus was slower than that of female pronucleus.
