Fatty Acid Composition of Bovine Embryos Cultured in Serum-Free and Serum-Containing Medium during Early Embryonic Development

Abstract

A serum-free culture system was used to allow determination of the fatty acid composition of bovine embryos during in vitro development. The proportion of embryos developing to the blastocyst stage in serum-free medium (TCM199 supplemented with bovine serum albumin, insulin, apotransferrin and transforming growth factor-α; BITTα) was as high as in serum-supplemented medium (TCM199+5% calf serum). Bovine blastocysts grown in serum-supplemented medium contained abundant lipid droplets in the cytoplasm. The fatty acid composition of bovine immature oocytes, embryos at 2-cell and blastocyst stages cultured in serum-free or serum-supplemented medium was determined by capillary column gas chromatography. Additionally, the fatty acid composition of calf serum alone was determined. Myristic acid (59.6%) was the most abundant fatty acid in immature oocytes followed by docosahexaenoic acid (12.3%). The fatty acid profiles of two-cell embryos derived in the serum-free medium were similar to those of immature oocytes. In contrast, two-cell embryos derived in the serum-supplemented medium showed high levels of palmitic (27.6%) and stearic (27.2%) acids and a low level of myristic acid (21.9%). For blastocysts grown in the serum-free medium, myristic acid (35.7%) was high and palmitic (17.0%) and stearic (12.5%) acids were moderately high. On the other hand, blastocysts developed in the serum-supplemented medium retained high levels of palmitic (30.5%) and stearic (24.2%) acid compositions and had considerably increased levels of palmitoleic (16.3%) and oleic (12.1%) acids. High levels of oleic (17.3%), palmitic (16.5%) and stearic (12.3%) acids were detected in calf serum, which were similar to the profile of the 2-cell and blastocyst stage embryos cultured with serum. This study shows that bovine embryos grown in serum-supplemented medium showed different morphology and fatty acid composition when compared to those cultured in serum-free medium.