Effects of Chemical Activation Treatment on Development of Swamp Buffalo (Bubalus bubalis) Oocytes Matured In Vitro and Fertilized by Intracytoplasmic Sperm Injection

Abstract

Contents: The objective of this study was to optimize the activation protocol for buffalo oocytes after intracytoplasmic sperm injection (ICSI). The release of the second polar body (PB) at 3, 6 and 9 h after ICSI of in -vitro matured oocytes activated either with 5 μm ionomycin (Io) or with 7% ethanol (EtOH) was preliminary examined. The highest rate of second PB extrusion occurred at 3 h of activation, and the second PB extrusion in EtOH group was significantly higher than that in Io group. Oocytes that extruded the second PB were selected and cultured either with 1.9 mm 6 -dimethylaminopurine (6 -DMAP) for 3 h or with 10 μg/ml cycloheximide (CHX) for 5 h. Significantly higher rate of oocytes formed 2 pronuclei in EtOH combined with CHX (EtOH + CHX) (62%) group compared to those of Io + CHX (42%) and EtOH + 6 -DMAP (48%) groups (p < 0.01) whereas Io + 6 -DMAP group showed intermediate value (58%). Significantly higher blastocyst formation rates were obtained in Io + 6 -DMAP (29%) and EtOH + CHX (24%) groups than in Io + CHX (6%) and EtOH + 6 -DMAP (17%) groups. Our results indicate that buffalo ICSI oocytes are effectively activated by combination treatment of Io with 6 -DMAP and EtOH with CHX resulting in the highest cleavage and blastocyst formation rates. © 2010 Blackwell Verlag GmbH.