Abstract: The lipids were extracted by using methanol and chloroform to make egg yolk solution from one phase into two phases;different components of yolk lipids were separated with three-dimensional thin layer chromatogram (TLC). Lipids weremethylated and determined by GC equipped with 100m×0.25mm capillary column. The results of TLC indicated that yolklipids contained cholesterol, triglyceride, cholesterol ester, free fatty acids, phosphatidylethanolamine, phosphatidylcholine andsphingomyelin. From the results of GC, the concentrations of fatty acids 16:0, 18:0, 9c18:1, 18:2n6 were highest. The rates oftrans and cis 18:1, and the rates of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) in the eggs hatched byfree run hens were significantly decreased compared with those of caged hens (1.34% vs 0.69%, 42.38% vs 39.06%, 39.74% vs37.90% and 47.09% vs 43.30% respectively), but the rate of total of polyunsaturated fatty acids (PUFA) was very significantlyincreased (12.09% vs 17.39%). It was resulted from the increment of 18:2n6 and ω3 (9.91% vs 14.64% and 0.23% vs 0.44%).The concentration of SFA (30.40%) was very significantly decreased in ω3 Egg2 compared with that of eggs from caged and freerun hens, but the rate of total of polyunsaturated fatty acids (PUFA) was very significantly increased to 25.56%. It was causedby the increment of 18:3n3 and ω3 (7.55% and 1.67%). Different feed types for hens could affect the proportion of some fattyacids in eggs yolk.

Key words: feed type, egg, lipids, extraction, determination