Effect of cytoplasmic lipid content on in vitro developmental efficiency of bovine IVP embryos

The objective was to evaluate the effect of cytoplasmic lipid content on the embryonic developmental efficiency of bovine in vitro embryo production (IVP) embryos. Ovaries from Korean native cows (Bos taurus coreanae) were collected from a local abattoir, and cumulus-oocyte complexes (COCs) were recovered from follicles 2 to 8mm in diameter. The oocytes were divided into three groups, dependent on their cytoplasm color: pale color (PC), brown color (BC), and dark color (DC). The COCs were fertilized using frozen-thawed semen from a single Hanwoo bull. Based on measurement of the cytoplasmic color intensity of oocytes after 22h of in vitro maturation (IVM), the DC group had lower (P<0.05) color intensity than that in the BC and PC groups (56.3+/-2.7, 93.3+/-5.1, and 123.9+/-12.0, respectively). Based on MitoTracker Green FM staining, the number of mitochondria in the DC (170.1+/-31.2) group was significantly higher than that in the BC (137.5+/-30.8) and PC (105.5+/-25.3) groups. The cleavage rate in the DC (81.5%) group was also higher than that in the PC (50.4%) group (P<0.05), as was the development rate to blastocyst stage (18.9% vs. 9.8%). Finally, cell numbers of blastocysts in the DC (150.8+/-28.0) group were higher (P<0.05) than that in the BC (107.6+/-17.8) and PC (80.5+/-12.3) groups. In conclusion, cytoplasm color was a useful selection parameter for abattoir-derived oocytes destined for IVP.