________________________________________________________________________________ Abstract The antioxidant enzyme, copper zinc superoxide dismutase (CuZnSOD) plays an important role in protecting tissues from damage by reactive oxygen species (ROS) reactions. The objective of this investigation was to determine the CuZnSOD mRNA level as an indicator of CuZnSOD activity and the effect it has on meat quality in three important pig breeds in China, the Laiwu Black (LW), Lulai Black (LL) and Large

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... rkshire (LY). Thirty six castrated boars (114 kg; LW, n = 12; LL, n = 12 and LY, n = 12) were used in this study. Samples were taken from the longissimus dorsi muscle, backfat and liver. Results showed that there was a significant breed × tissue interaction; and the maximum mRNA level of the CuZnSOD gene was recorded in the LW and the minimum in the LY. The proportion of gene expression was positively correlated with the anti-oxidative capacity in muscle. The expression of the CuZnSOD gene was positively correlated with meat colour and tenderness; and negatively correlated with marbling score, drip loss, cooking loss and intramuscular fat. The higher the level of CuZnSOD mRNA expression, the better was the quality of the pork. This implies that the difference in CuZnSOD mRNA expression in breeds was involved in the mechanisms of meat quality that related to superoxide dismutase (SOD) activity and anti-oxidant capacity of the muscle.