Effects of conjugated linoleic acid on the belly firmness and fatty acid composition of genetically lean pigs

A study of the effects of conjugated linoleic acid (CLA) on the belly firmn ess and fatty acid composition of genetically lean pigs was conducted. From 75 to 120 kg live weight, 30 gilts were allowed ad libitum access to a cor n-soybean meal diet supplemented with either 1% CLA oil (CLA-60) or 1% sunf lower oil (SFO) or were fed the sunflower oil-supplemented diet restricted to the amount consumed by pigs fed the CLA-60 diet (RSFO). Conjugated linol eic acid oil consists of 60% positional and geometric isomers of CLA. Pigs fed SFO exhibited higher average daily gains (0.98 vs 0.80 kg/d, P < 0.01) than RSFO-fed pigs, but there were no effects of dietary treatment on feed intake or feed efficiency. Dietary treatment did not affect (P > 0.05) back fat thickness or longissimus muscle area. Bellies of gilts fed CLA-60 were subjectively evaluated to be firmer (2.91 vs 2.43 or 2.07 +/- 0.13, P < 0.0 1) than those of SFO- or RSFO-fed gilts, respectively. The longissimus musc le of gilts fed CLA-60 contained more saturated fatty acids (39.77 vs 36.04 or 36.73 +/- 0.74%, P < 0.001) and less unsaturated fatty acids (60.23 vs 63.96 or 63.27 +/- 0.74%, P < 0.001) than that of gilts fed SFO or RSFO, re spectively. The belly fat of gilts fed CLA-60 contained more saturated fatt y acids (44.45 vs 37.50 or 36.60 +/- 0.46%, P < 0.001.) and less unsaturate d fatty acids (54.78 vs 61.75 or 62.47 +/- 0.46%, P < 0.001), resulting in lower iodine values (57.69 vs 66.37 or 65.62 +/- 0.91, P < 0.001) than that of gilts fed SFO or RSFO, respectively. Gilts fed CLA-60 accumulated more CIA in the longissimus muscle (0.55 vs 0.09 or 0.09 +/- 0.03%, P < 0.01) an d belly fat (1.56 vs 0.13 or 0.13 +/- 0.15%, P < 0.001) than did gilts fed SFO or RSFO, respectively. Dietary treatment did not affect (P > 0.05) 24-h pH, drip loss or subjective quality evaluations of the longissimus muscle. The effect of supplemental CLA to improve belly firmness is of practical s ignificance and may provide a nutritional solution to carcass fat and belly firmness problems, thereby enhancing the overall value of extremely lean c arcasses.