Effects Of Exercise On Muscle Fiber Characteristics And Meat Quality Of Sunit Sheep

To investigate the effect of exercise on muscle fiber characteristics and meat quality of Sunit sheep,14 Sunit sheep were randomly divided into control group（C）and exercise group（E）.The control group was raised in a semi-open sheep shed,and the exercise group carried out 6 km+driving exercise every day under the same environment,the pre-test period was 7 days and the test period was 90 days.The effects of exercise on meat quality,characteristics of muscle fiber,mechanisms of skeletal muscle energy metabolism and muscle development in Sunit sheep were investigated by ATP enzyme histochemical staining and real-time fluorescence quantitative PCR（QPCR）and Western blotting.The effects mechanism of exercise on muscle fiber characteristics and meat quality in Sunit sheep was initially investigated.The study on the characteristics of muscle fiber in Sunit sheep showed that compared with the control group,the cross-sectional area of type I muscle fiber,the diameter and area ratio of typeⅡA muscle fiber,and the expression of MyHCⅡa in the LD muscle and BF muscle were increased markedly,and the area and quantity ratio of typeⅡB muscle fiber were markedly decreased（P<0.05）.The diameter and cross-sectional area of typeⅡB muscle fibers in BF were increased markedly（P<0.05）.In this experiment,the diameter and cross-sectional area of various muscle fibers in Sunit sheep were increased by increasing exercise,and the proportion of oxidized muscle fibers was enhanced.The determination of muscle lactic acid,glycogen content and muscle metabolism-related enzyme activity showed that the CK enzyme activity in the LD muscle and biceps femoris muscle of the exercise group was increased markedly than that of the control group（P<0.05）,and the glycogen content was markedly decreased than that of the control group（P<0.01）.The activities of SDH and HK in the LD muscle in the exercise group were remarkably elevated than those in the control group（P<0.05）,which indicated that increasing exercise was beneficial to improve the oxidative metabolism of muscle.The meat quality of Sunit sheep were compared.Compared with the control group,the net meat rate of the exercise group was significantly increased（P<0.01）,the slaughter rate was significantly increased,and the backfat thickness was markedly decreased（P<0.05）.The ash content decreased significantly,the shear force value increased significantly in the two muscle parts（P<0.05）,the pH₀value decreased significantly,and the pH₂₄value increased markedly（P<0.01）.The intramuscular fat content in the LD muscle was significantly decreased（P<0.05）.These show that increasing exercise can delay the decline of pH,reduce ash and intramuscular fat content,but not conducive to muscle tenderness.Through the study of skeletal muscle energy metabolism and muscle hypertrophy in Sunit sheep,it was found that exercise significantly up-regulated AMPKα1 mRNA expression（P<0.01）,and SIRT1 mRNA,PGC-1αmRNA expression,p-AMPK and p-AMPK/AMPK protein expression were significantly up-regulated in the LD of Sunit sheep（P<0.05）,AMPKα1 mRNA,SIRT1 mRNA,COXⅣmRNA,PGC-1αmRNA and p-AMPK/AMPK protein expression in biceps femoris were significantly up-regulated（P<0.05）.By exploring the skeletal muscle development of Sunit sheep,it was found that the relative expression levels of p70s6k1 mRNA and 4EBP1 mRNA,p AKT/AKT and p-p70s6k/p70s6k in the LD muscle of Sunit sheep were increase remarkably than those in the control group（P<0.05）.The relative expression of mTOR,p70s6k1 mRNA,AKT and p70s6k protein in BF were elevate significantly than those in control group（P<0.05）,and the relative expression of AKT mRNA was increase remarkably than that in control group（P<0.01）.Combined with the results of muscle fiber characteristics analysis,exercise may promote skeletal muscle energy metabolism by mediating AMPK/PGC-1αpathway,thus promoting the transformation of glycolytic muscle fibers to oxidized muscle fibers.By mediating AKT/mTOR pathway,skeletal muscle growth and development and muscle fiber selective hypertrophy are promoted,thereby improving muscle function.