Chemical activation of buffalo (Bubalus bubalis) oocytes by different methods: effects of aging on post-parthenogenetic development

The possibility of artificially inducing activation of MII buffalo oocytes may allow us to evaluate indirectly the quality of oocytes after in vitro maturation. The aim of this work was to compare buffalo embryo development after IVF and after chemical activation by two different agents. A further goal was to evaluate the effects of aging of oocytes on post-parthenogenetic and post-fertilization development. In Experiment 1 cumulus–oocyte complexes (COCs) were recovered from abattoir-derived ovaries and matured in vitro. After IVM the COCs were either fertilized in vitro (positive control) or activated with ethanol and ionomycin, both followed by immediate exposure to 6-diethylaminopurine (6-DMAP) for 4 h. In vitro culture (IVC) was carried out up to the blastocyst stage. In Experiment 2 COCs were matured in vitro for 18, 21, 24, 27 and 30 h before activation was triggered with ethanol, followed by 6-DMAP. In Experiment 3 COCs were fertilized in vitro at 18, 21, 24, 27 and 30 h post-maturation. Ethanol activation gave better results than the IVF control group, with higher cleavage rate (71.4±7.8 versus 55.8±5.8, respectively; P<0.05) and a higher proportion of oocytes developing into morulae-blastocysts (32.6±6.5 versus 22.9±7.5, respectively; P<0.05). Within the activation groups, ethanol supported the highest development in terms of cleavage (71.4±7.8 versus 59.4±10.7; P<0.05) and morulae-blastocysts rate (32.6±6.5 versus 25.7±8.3; n.s.). It was also demonstrated that aging negatively affects post-parthenogenetic and post-fertilization development.