Developmental competence of cat (<italic>Felis domesticus</italic>) oocytes and embryos after parthenogenetic stimulation using different methods.

Summary: The aim of this study was to compare the effects of various activating factors on feline oocytes. The study included activation within the ovary (natural), activation during <italic>in vitro</italic> maturation (spontaneous activation), chemical activation (ionomycin + 6-DMAP), activation by spermatozoa and injection (ICSI) and mechanical activation (sham ICSI). According to our results, parthenogenetic embryos could emerge at every step of <italic>in vitro</italic> embryo production (IVP) procedures. After oocyte collection, 6% of parthenogenetic embryos were observed, mainly at the 2–4-blastomere stages. After 24 h of <italic>in vitro</italic> maturation, parthenogenetic activation was observed in 7% of oocytes. Using ionomycin and 6-DMAP to artificially activate oocytes, 53% of cleaved embryos were obtained. The results after ICSI (54% cleaved embryos) were not significantly different from the results in Group III using chemical activation (53% cleaved embryos). But only after ICSI were blastocysts obtained (5/73.7%) as a result of <italic>in vitro</italic> culture. Moreover, embryos after ICSI were of the best morphological quality with minor levels of fragmentation evident in the embryos. After sham mechanical activation, ‘sham ICSI’, 8% of cleaved embryos were noted. Therefore, it is advised to maintain a negative control in parallel with each step of IVP techniques, to avoid misleading results. Chemical methods for artificial activation of feline oocytes are the most promising for application to the cloning and production of parthenogenetic embryos for experimental studies. [ABSTRACT FROM AUTHOR]