BACKFAT FATTY-ACID EVOLUTION IN SWINE FED DIETS HIGH IN EITHER CIS-MONOUNSATURATED, TRANS, OR (N-3) FATS

To evaluate the effects of dietary fats on the evolution of the fatty acid profile of swine backfat, 30 castrated Landrace x Duroc pigs aver aging 26 kg were assigned three diets with 4% added pomace oil(O), hyd rogenated fat (H), or linseed oil (L). Subcutaneous fat samples were t aken from biopsies at 0, 17, 31, and 60 d, and at 24 h postmortem when pigs averaged 95 kg live weight at 82 d on trial. On d 17, saturated fatty acid (SFA) content was 2% lower for the O diet than for I-I and L (P < .089). There was a linear increase in SFA at a monthly rate of 2% in the three diets. The increase was mainly due to 18:0; palmitic a cid percentages showed no variation. Pigs fed the O diet experienced e xponential increases in monounsaturated fatty acids (MUFA), especially until d 17 (P < .001). In pigs fed the H or L diets, MUFA contents de creased at a monthly rate of 2.40%, and the same happened with oleic a cid contents. Diets rich in (n-3) (L) and trans-fatty acids (H) caused exponential increases in swine backfat contents of total (n-3) and to tal trans, respectively. At d 31 (P < .001), 72 to 73% of the maximum contents had been reached. Contents for 20:3(n-3), 20:5(n-3), and 22: 5(n-3) follow a pattern similar to that of their precursor 18:3(n-3), showing an exponential increase in pigs fed the L diet, and contents f or H and O treatments were lower (P < .001). The three diets caused a linear decrease in (n-6) fatty acid contents throughout the 82-d trial .