Effects Of Feeding Regimen On Energy Metabolism And Meat Quality During Post-mortem Aging Of Sunit Sheep

The longissimus dorsi and biceps femoris of Sunit sheep in different feeding regimens(pasture and confinement)were used as experimental materials to postmortem aging at4 ℃ for 0 h,24 h,48 h,72 h and 96 h.The differences and changes of related indexes of meat quality,AMPK activity,glycolysis and lipid metabolism were measured and analyzed.The results are as follows:The effect of feeding regimens on postmortem meat quality of Sunit sheep was studied.The results showed that the shear force of longissimus dorsi muscle of pasture sheep was significantly lower than that of confinement sheep at 0-72 h during postmortem aging(P < 0.05).The shear force of biceps femoris was significantly lower than that of sheep at 0-24 h during postmortem aging(P < 0.05).The MFI value of longissimus dorsi muscle of pasture sheep was significantly higher than that of confinement sheep at all time points during postmortem aging(P < 0.05),and the MFI value of biceps femoris muscle was significantly higher than that of confinement sheep at 24-96 h during postmortem aging(P < 0.05).The postmortem cooking loss of longissimus dorsi muscle of pasture sheep was significantly lower than that of confinement sheep(P < 0.05),and the cooking loss of biceps femoris was significantly lower than that of confinement sheep only at 96 h(P < 0.05).The nonanal content of longissimus dorsi muscle of pasture sheep was significantly higher than that of confinement sheep(P < 0.05),and the content of n-octanal in 24-72 h during postmortem aging was significantly higher than that of confinement sheep(P < 0.05).The contents of hexanal and 2-ethylhexanol in biceps femoris muscle of pasture sheep were significantly higher than those of confinement sheep(P < 0.05),the content of decanal was significantly lower than that of confinement sheep(P < 0.05),and the contents of 1-octene-3-ol and 2-methyl-3-heptanone were significantly lower than those of confinement sheep(P < 0.05).The cooking loss and L* value of longissimus dorsi and biceps femoris in both groups increased with the prolongation of postmortem aging time,and the a * and b * values increased significantly at 0-24 h during postmortem aging(P < 0.05).After 48 hours of postmortem aging,the p H value of meat began to increase,the shear force decreased,and the tenderness became better.At the same time,postmortem aging increased the relative contents of some key flavor substances in mutton,such as hexanal,1-octene-3-ol and 2-ethylhexanol.Combined with the above data,it can be shown that pasture mutton has good tenderness and water retention.Meanwhile,the mutton after48 hours of postmortem has better quality and is suitable for processing and eating.The effects of feeding regimens on postmortem energy metabolism of Sunit sheep were studied.The results showed that the p-AMPK,HK,PFK,MUFA ratio,T-AOC and GSH-Px in longissimus dorsi and biceps femoris of pasture sheep were significantly higher than those of confinement sheep(P < 0.05),while the activities of ACC,FAS and MDA value were significantly lower than those of confinement sheep(P < 0.05).The content of glycogen in longissimus dorsi muscle of pasture sheep was significantly lower than that of confinement sheep during postmortem aging(P < 0.05),and the glycogen content of biceps femoris muscle was significantly lower than that of confinement sheep only at 0 and48 h after postmortem(P < 0.05).The lactic acid content in longissimus dorsi muscle of pasture sheep was significantly higher than that of confinement sheep at 0 and 96 h after postmortem(P < 0.05),and the lactic acid content of biceps femoris muscle was significantly higher than that of confinement sheep at 24 and 96 h after postmortem(P <0.05).The activity of LDH in longissimus dorsi muscle of pasture sheep was significantly higher than that of confinement sheep at 0,48 and 72 h after postmortem,and the activity of LDH in biceps femoris muscle was significantly higher than that of confinement sheep at 24 and 48 h after postmortem.The above data showed that pasture could increase the activities of p-AMPK and glycolysis-related enzymes in sheep after postmortem,and accelerate the rate of glycolysis of mutton in a reasonable range.At the same time,it can optimize the composition of fatty acids in meat,improve the oxidative stability of meat,inhibit the activities of ACC and FAS,and reduce the degree of lipid oxidation of meat.During the postmortem aging,the changes of PFK,competition,ATGL activity and lactic acid content in the muscle of the two groups were consistent with the p-AMPK activity,which increased at first and then decreased,while the ACC and FAS activity decreased at first and then increased,which indicated that the post-postmortem AMPK of the two groups could control the glycolysis process by phosphorylating the key enzymes of glycolysis,affecting the p H value,water retention and tenderness of meat.Moreover,it can affect the composition and oxidation of fatty acids by activating ATGL and inhibiting the activities of ACC and FAS,thus affecting the color and flavor of meat.The activities of TAOC,antioxidant enzymes,the ratio of MUFA and PUFA gradually decreased,while the MDA value increased,which indicated that with the extension of postmortem aging time,the antioxidant capacity of the two groups gradually decreased,while the degree of lipid oxidation gradually increased.