Change in the composition of free fatty acids in plasma of swine during growth

Concentration of plasma free fatty acids (FFAs), the decomposition products of body fats, of the six Landrace were determined by gas chromatography/mass spectrometer system (GC/MS) to examine the relationship between the body weights and the composition as well as concentration of FFAs in plasma. Blood samples were collected in the fed state at 30, 50 and 70kg, and in the fasted state at 90kg in live weight. The FFAs were assayed by firstly extracting lipids from plasma, isolating them by thin layer chromatography, converting the FFA fraction into methyl esters, infusing the methyl esters into a GC/MS and then quantifying the methyl esters by selected ion monitoring method (SIM) using methyl pentadecanoate as an internal standard. The monitored ions of 14:0, 15:0, 16:0, 16:1, 18:0, 18:1 and 18:2 were m/z=74.0, 74.0, 74.0, 236.3, 298.3, 264.3 and 294.3, respectively. FFA sampled from plasma of the swine in fed state had higher percentage of palmitic acid (16:0) and linoleic acid (18:2), and a lower percentage of oleic acid (18:1) than the counterparts from their subcutaneous fat. Findings on the change in the composition of FFAs in plasma during growth of swine revealed that saturated FFAs increased and linoleic acid (18:2) decreased as swine grew up, as seen in the subcutaneous fat. The concentration of FFAs after the fasting amounted to approximately five times of that in fed state, and the composition of FFAs became very much similar to that of subcutaneous inner layer fat.