The study was conducted to investigate the effects of dietary ideal protein level on tenderness and mRNA expression level of CaN-NFAT signaling pathway related to0020proteins and CAST of longissimus dorsi in finishing pigs. Ninety crossbred pigs (Duroc × Landrace × Large white, about 50 kg BW) were randomly allocated into 3 treatments with 3 replicates and per treatment 10 heads per replicate. Pigs in the three treatments were fed diets with the same energy level and ideal protein levels at 12%, 16% and 20%, respectively. All pigs were slaughtered after 58 days experiment and muscle samples were collected for the analysis of shear force, as well as mRNA expression levels of CAST, CaN, CaM and NFAT of longissimus dorsi in finishing pigs were determined by real-time PCR. The results showed as follows: 1) High dietary protein level significantly increased the shear force (P<0.05) and mRNA expression levels of CaN and CAST of longissimus dorsi (P<0.01). 2) The shear force was positively correlated with the mRNA expression levels of CAST (coefficient correlation=0.713, P<0.01); the mRNA expression levels of NFAT (coefficient correlation=0.536, P<0.05) and CaM (coefficient correlation=0.546, P<0.05) were positively correlated with that of CaN; the mRNA expression levels of CaM and NFAT were positively correlated (coefficient correlation=0.623, P<0.05) to each other. The results indicate that high dietary protein level can significantly decrease the tenderness, but increase mRNA expression levels of CAST and CaN of longissimus dorsi; the tenderness of longissimus dorsi is positively correlated with CAST mRNA expression level, but is not correlated with the CaN-NFAT signaling pathway.［Chinese Journal of Animal Nutrition, 2011, 23（7）：1153 -1160］
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