Effects of ractopamine administration and castration method on muscle fiber characteristics and sensory quality of the longissimus muscle in two Piétrain pig genotypes

Abstract Single and combined effects of ractopamine supplementation (RAC, 7.5 vs. 0 ppm), castration method (surgical castration: SC vs. immuno-castration: IM) and genotype (genotype A: GA vs. GB containing 25% or 50% Pietrain) were determined on longissimus muscle (LM) fiber traits and quality of pork ( n  = 512). RAC increased fiber IIX cross-sectional area ( P  = 0.009) and decreased glycolytic potential ( P  = 0.02) and pork tenderness ( P P P  = 0.04) off-flavor score and WBSF than SC. LM from GB pigs was paler ( P P