Dietary C18 : 1 trans fatty acids increase conjugated linoleic acid in adipose tissue of pigs

The effect of dietary C18:1 trans fatty acids on back fat composition in pi gs was investigated with special emphasis on conjugated linoleic acids (CLA ). A total of 12 x 4 siblings of Large White and Swiss Landrace breed were housed in groups and fattened from 22 to 103 kg live weight. Pigs were fed a control diet (barley, wheat, soybean meal) or experimental diets which co nsisted of the control diet with a 5% replacement of olein or stearin fract ions of pork fat, or partially hydrogenated fat. The hydrogenated fat was r ich in C18:1 trans fatty acids but contained only negligible amounts of CLA . in contrast olein and stearin fractions contained far less C18:1 trans fa tty acids but some CLA, in the control diet no C18:1 trans fatty acids and only traces of CLA were detected. The partially hydrogenated fat led to the highest CLA content in back fat (0.44%). intermediate amounts of CLA were measured in pigs fed the fractionated pork fat (0.22/0.23%). In pigs fed th e control diet, also small amounts of CLA were detected. The results indica te that CLA may be produced by endogenous Delta9-desaturation out of dietar y trans vaccenic acid in pigs.