Abstract: The effect of different feeding methods on AMP-activated protein kinase (AMPK) and glycolysis in longissimus dorsi muscle from Sunit sheep were investigated in this study. The results showed that longissimus dorsi muscle from grazing sheep exhibited significantly higher Warner-Bratzler shear force, L* and b* values when compared with pen-reared sheep (P < 0.05). The pH1 and pH24 of longissimus dorsi were not significantly between different feeding methods (P > 0.05). PRKAA1 and PRKAG3 gene expression in pen-fed sheep were significantly higher than in grazing sheep (P < 0.05), but the opposite was found for PRKAA2 gene expression (P < 0.05). AMPK and hexokinase activity under pen-fed conditions were higher but not statistically significantly than under grazing conditions (P > 0.05). Lactic acid content under pen-fed conditions was significantly higher than under grazing conditions (P < 0.05). Correlation analysis revealed that PRKAG3 gene expression positively regulated AMPK activation, hexokinase activity and lactic acid content (P < 0.05), but had a significantly negative correlation with Warner-Bratzler shear force (P < 0.05). PRKKA1 gene expression and lactic acid content were significantly positively correlated with each other (P < 0.05), while PRKKA2 had no significant correlation with AMPK or glycolysis indicators. AMPK activity was significantly positively correlated with hexokinase activity and lactic acid content (P < 0.05). From the above results, we concluded that high levels of PRKAA1 and PRKAG3 gene expression resulted in AMPK activation and consequently an increase in hexokinase activity, thereby accelerating the process of glycolysis, increasing lactic acid content, reducing pH and consequently affecting meat quality.

Key words: Sunit sheep, feeding conditions, AMP-activated protein kinase, glycolysis