Fatty acid composition of backfat in large white pigs selected for low backfat thickness

Samples of midback fat were taken from 157 Large White boars and analysed for fatty acid composition and melting point of lipid. Seventy-seven boars were from a line showing fast efficient growth and low backfat depth (selection line) and 80 from a random-mated control line. All were performance-tested from 27 to 87 kg liveweight on ad libitum feeding. Selection line pigs required 6 % less feed per kilogramme liveweight gain and had thinner backfat at each point of measurement (16-27 %) than the controls but there was no line difference in daily liveweight gain. Selection line pigs had 'eye muscles' which were slightly paler and had a greater drip loss than the controls. The fatty acid composition and melting point of the lipid extracted from backfat was similar between the lines except that the concentration of linoleic acid (C18:2) in both inner and outer layers was some 14% higher in the selection line. There were significant negative correlations between the concentration of C18:2 and the various backfat measurements. Positive correlations were found between some backfat measurements and the concentration of stearic acid (C18:0), particularly in the selection line. Variation in melting point in both layers was more strongly related to variation in the concentration of C18:0 than to that of any other fatty acid.