Effects Of Different Energy Feeding Strategies On Glycometabolism And Meat Quality Of Hu Sheep

With the rapid development of our mutton industry and the continuous rise of mutton trade,the consumption demand will strive for higher meat quality.Glycometabolism plays an important role in the production performance of animals.Different energy levels and energy supply modes in diets can affect the body glycometabolism,and then affect the meat quality.In this study,Hu sheep were taken as the research object,and the effects of different energy feeding strategies（i.e.,different energy feeding levels and supply modes）on glycometabolism and meat quality of Hu sheep were studied.A total of 96 healthy weaned male lambs aged 3 months（with a body weight of 17.22±0.02 kg）were randomly divided into 4 groups,with 6 replicates per group and 4 lambs per replicate.The pre-trial period was 15 days,and the formal trial period was 90 days.The lambs were divided into four groups based on different energy feeding strategies:low energy group（L-L group,fed low-energy feed throughout the trial period with a metabolizable energy of 8.83 MJ/kg）,high energy group（H-H group,fed high-energy feed throughout the trial period with a metabolizable energy of 10.84 MJ/kg）,low-high energy group（L-H group,fed low-energy feed in the first 60 days and high-energy feed in the last 30 days）,and high-low energy group（H-L group,fed high-energy feed in the first 60 days and low-energy feed in the last 30 days）.The experimental results are as follows:Section 1:Effects of different energy feeding strategies on glycometabolism in Hu sheep.After the experiment,blood samples were collected from the jugular vein of two Hu sheep from each replicate that were close to the average body weight in the group,and 5 m L of blood was collected to prepare serum.About 10g of liver and longissimus dorsi tissue was collected immediately after slaughter and placed in sterile cryopreservation tube.To determine the index of glycometabolism of Hu sheep.The results showed that:（1）The impact of different energy feeding strategies on glucose,pyroracemic acid,lactic acid concentrations and lactic dehydrogenase activity in Hu sheep serum were not significant（P>0.05）.（2）The hepatic glycogen content of the H-H and L-H groups was significantly higher than that of the H-L and L-L groups（P<0.05）.The phosphoenolpyruvate carboxykinase of the H-H and H-L groups was significantly higher than that of the L-L group（P<0.05）.The pyruvate carboxylase and glucose-6-phosphatase in the H-L group were significantly higher than those in L-H and L-L groups（P<0.05）.（3）The muscle glycogen content in H-L and L-L groups was significantly higher than that in H-H and L-H groups（P<0.05）.The pyroracemic acid content,lactic acid content,hexokinase,phosphofructokinase,pyruvate kinase and glycolysis potential in H-L and L-L groups were significantly lower than those in H-H and L-H groups（P<0.05）.The ATP content of the H-H group was significantly higher than that of the other three groups,the ADP content of the L-L and H-L groups was significantly higher than that of the L-H and H-H groups,and the AMP content of the H-H group was the lowest,and the AMP content of the L-L group was significantly lower than that of the H-L group（P<0.05）.Section 2:Effects of different energy feeding strategies on meat quality of fattening Hu sheep.At the end of the experiment,one sheep in each replicate of each group with a body weight close to the average in the group was slaughtered.,and 250 g of the middle of the longissimus dorsi in the left half of the carcass was used to measure meat quality indicators.The results showed:（1）The protein content of mutton in the L-L group was the highest,and the H-H group had the lowest protein content（P<0.05）.The fat content of mutton in the H-H group was significantly higher than that in the other three groups,and the H-L group was significantly higher than the L-H and L-L groups（P<0.05）.（2）The p H₀,p H₂₄,and shear force of mutton in the H-H group were significantly lower than those in the other groups（P<0.05）.The p H₂₄of the H-L group was significantly lower than that of the L-L group（P<0.05）.The lightness value of mutton in the H-H group was significantly higher than that in the other groups（P<0.05）.（3）The saturated fatty acid,C15:0,C17:0,C18:0,and C20:0 content in mutton from the H-H group and L-H group were significantly lower than those in the L-L group and H-L group（P<0.05）.The unsaturated fatty acid,C18:1n-9c content,and UFA/SFA in mutton from the H-H group and L-H group were significantly higher than those in the L group and H-L group（P<0.05）.The monounsaturated fatty acid content in the L-H group was significantly higher than that in the L-L group and H-L group（P<0.05）.（4）The muscle fiber area and muscle fiber diameter of mutton in the H-H group and H-L group were significantly smaller than those in the L-L group and L-H group,and the muscle fiber area of mutton in the H-H group was significantly smaller than that in the H-L group（P<0.05）.（5）In the expression level of myosin heavy chain（My HC）gene,the expression level of My HC-I in mutton from the H-H group was significantly higher than that in the L-L group and L-H group,and the expression level of My HC-I in mutton from the H-L group was significantly higher than that in the L-L group（P<0.05）.Section 3:Correlation analysis of glycometabolism and meat quality in fattening Hu sheep under different energy feeding strategies.The results showed that:（1）Blood glucose content was significantly positively correlated with moisture,unsaturated fatty acids,and polyunsaturated fatty acids in meat quality,and significantly negatively correlated with yellowness and redness,as well as saturated fatty acids（P<0.05）.（2）Hepatic glycogen was significantly negatively correlated with protein content,p H0,p H24,shear force,saturated fatty acid and muscle fiber area in meat quality,but was significantly positively correlated with fat content,meat color brightness,unsaturated fatty acid and monounsaturated fatty acid（P<0.05）.The contents of glucose,pyroracemic acid content,phosphoenolpyruvate carboxykinase and glucose-6-phosphokinase in liver were significantly negatively correlated with protein content,but significantly positively correlated with fat content（P<0.05）.（3）The p H₂₄,muscle fiber diameter and muscle fiber area in meat quality were significantly positively correlated with muscle glycogen and ADP contents,but significantly negatively correlated with pyroracemic acid,lactic acid,ATP,pyruvate kinase,phosphofructokinase and glycolysis potential（P<0.05）.Saturated fatty acids were significantly positively correlated with muscle glycogen and ADP,and significantly negatively correlated with pyroracemic acid,lactic acid,hexokinase,pyruvate kinase,phosphofructokinase,and glycolytic potential.Unsaturated fatty acids and monounsaturated fatty acids are opposite to the correlations of saturated fatty acids（P<0.05）.In conclusion,energy level at early dietary stage plays a decisive role in muscle fiber type and characteristics,while energy level at late dietary stage has a significant effect on glycometabolism and is closely related to fatty acid composition and content.Therefore,the high energy feeding strategy in the early stage and low energy feeding strategy in the late stage can better regulate the glycometabolism pathway,slow down the glycolysis rate of slaughtered muscle,and make the fat and protein content,meat color,shear force and system water of mutton better.