Effects of Soybean Meal Substitution in Finishing Pig Diet on Carcass Traits, Meat Quality, and Muscle Antioxidant Capacity

This study evaluated the effect of mixed meal replacement of soybean meal on growth conditions, carcass traits, and meat quality of finishing pigs by partially and entirely replacing soybean meal with equal proportions of rapeseed, cotton, and sunflower meal. A total of fifty-four pigs with an average initial weight of 97.60 ± 0.30 kg were selected and randomly divided into three groups according to their initial weight, with six pens in each group and three pigs in each pen. The experimental groups were as follows: control group (CON), fed corn-soybean meal type basal diet; corn-soybean mixed meal group (CSM), using equal proportions of rapeseed meal, cotton meal, and sunflower meal (3.52% each) to replace 9.06% of soybean meal in the basal diet; and corn mixed meal group (CMM), using equal proportions of rapeseed meal, cotton meal, and sunflower meal (6.46% each) to replace soybean meal in the basal diet completely. According to the results, the use of mixed meal as a replacement for soybean meal did not have a significant impact (<i>p</i> > 0.05) on the average daily weight gain, average daily feed intake, feed-to-weight ratio, body size, carcass traits, and meat quality of finishing pigs. The entire replacement of soybean meal with a mixed meal resulted in a significant increase (<i>p</i> < 0.05) in leaf fat weight. The use of mixed meal as a substitute for soybean meal had no significant effect (<i>p</i> > 0.05) on the antioxidant capacity and fatty acid composition of the longissimus thoracis in finishing pigs. However, longissimus thoracis muscle fiber diameter was reduced in the mixed meal partially replaced soybean meal group compared to the mixed meal completely replaced soybean meal group (<i>p</i> < 0.05). In addition, mixed meal replacing soybean meal did not significantly affect (<i>p</i> > 0.05) the expression of the longissimus thoracis muscle fiber type genes <i>MYHC1</i> and <i>MYHC2</i>. Mixed meal replacement of soybean meal did not significantly affect (<i>p</i> > 0.05) the expression of <i>ACACA</i>, <i>FASN</i>, and <i>PPARG</i> genes in the longissimus thoracis. This study showed that mixed meal as an alternative to soybean meal in diets did not have significant negative effects on the growth performance and meat quality of finishing pigs. These results can help develop further mixed meals as a functional alternative feed ingredient for soybean meals in pig diets.