Effects of sperm pretreatment and embryo activation methods on the development of bovine embryos produced by intracytoplasmic sperm injection

The aim of the study was to examine the effects of different embryo activation methods and sperm pretreatments on the activation and development of bovine embryos produced by intracytoplasmic sperm injection (ICSI). Four activation agents, i.e., calcium ionophore (A23187), ionomycin (Ion), electric pulse (EP) and ethanol (Eth) were used in various combinations to activate bovine ICSI embryos. The normal fertilization rate was similar in bovine ICSI embryos activated by A23187 + Eth, Ion + Eth, Ion + EP + Eth, and 2-Ion (Ion administered two times) + Eth. Increasing the frequency of ionomycin stimulation from two (2-Ion + Eth) to three times (3-Ion + Eth) significantly (p < 0.05) increased the cell number per embryo at the blastocyst stage. In addition, spermatozoa were pretreated with dithiothreitol (DTT), glutathione (GSH) or GSH + lysolecithin (LL) and used for producing bovine ICSI embryos. The blastocyst rate of bovine ICSI embryos produced from sperm pretreated with GSH was significantly (p < 0.05) higher than those of embryos produced from sperm pretreated with DTT and GSH + LL. In conclusion, the embryo activation methods and sperm pretreatments examined in the present study did not affect the normal fertilization rate of bovine ICSI embryos. However, activation with 3-Ion + Eth and sperm pretreatment with GSH increased the cell number per embryo at blastocyst stage and the blastocyst rate, respectively, in bovine ICSI embryos.