Effect of the Presence Period of Bovine Leukemia Inhibitory Factor in Culture Medium on the Development of In Vitro Fertilized Bovine Embryos

The effects of the presence of bovine leukemia inhibitory factor (bLIF) in culture medium on the hatching rate and cell number of inner cell mass (ICM) and trophectoderm (TE) of bovine embryos were examined. Bovine presumptive zygotes were divided into four groups which were in the presence or absence of 10ng/ml of bLIF, and the culture period of the groups in the presence of bLIF was throughout from day 0 to 5 and/or day 5 to 10 (the day of in vitro fertilization was decided as day 0). The cleavage rate at day 2 was not significantly different among the four groups. Hatching rates of zygotes cultured in the presence of bLIF throughout from day 5 to 10 were significantly higher than those of zygotes cultured in the absence of bLIF throughout from day 5 to 10. The cell numbers of TE of hatched blastocysts obtained from zygotes cultured in the presence of bLIF throughout from day 5 to 10 were significantly higher than those of hatched blastocysts obtained from zygotes cultured in the absence of bLIF throughout from day 5 to 10. However, the cell numbers of ICM were not significantly different in the four groups. There were no effect of the presence of bLIF throughout from day 0 to 5 on hatching rate and cell number of ICM and TE. These results indicate that (1) the effect of bLIF depends on the period of its presence, (2) bLIF increases the number of cells in the TE and (3) bLIF acts on the hatching process.