Western and indigenous Chinese pig breeds show obvious differences in muscle growth and meat quality,however,the underlying molecular mechanism remains unclear.In this study,proteome analysis of longissimus dorsi muscle between purebred Meishan and Large White pigs was performed by 2-dimensional gel electrophoresis and mass spectrometry.A total of 25 protein spots were differentially expressed in the 2 breeds.The 14 identified proteins could be divided into 4 groups:energy metabolism,defense and stress,myofibrillar filaments,and other unclassified proteins.Quantitative real-time PCR was used to analyze the partly differentially expressed proteins in mRNA level,which revealed a positive correlation between the content of the proteins and their mRNA levels.We also analyzed the mRNA levels of myosin heavy chain isoforms using quantitative real-time PCR.The results indicated that Ⅱa and Ⅱx fibers were elevated in Meishan pigs,whereas the Ⅱb fiber was more highly expressed in Large White pigs.To the best of our knowledge,this was the first proteomics-based investigation of total skeletal muscle protein in different pig breeds,and these results may provide valuable information for understanding the molecular mechanism responsible for breed specific differences in growth performance and meat quality.