Effects Of Feeding Regimens On Muscle Fiber Characteristic And Meat Quality Of Sunit Sheep And Its Underlying Mechanism

The effects of feeding regimens(pasture and confinement)on slaughter performance,meat quality and basic nutrients of Sunit sheep were analyzed.And the characteristics of muscle fiber and its influence mechanisms were investigated by using ATPase staining,Real-time Quantitative polymerase chain reaction and TMT differences Proteomics technology.Then by dietary linseed or lactic acid bacteria supplementation,or increasing the amount of exercise to regulate the muscle fiber characteristics of confinement Sunit sheep,the result is as follows.The slaughter performance,meat quality and basic nutrients of Sunit sheep in different feeding regimens were measured,and the results showed that,compared with the confinement group,the carcass depth was significantly higher(P<0.05),and the carcass weight,carcass length,and slaughter rate,net meat rate and carcass meat-to-bone ratio were significantly lower in the pasture group(P<0.05).In the pasture group,the p H₂₄ and shear force values of the longissimus thoracis(LT)and biceps femoris(BF),and L*,the crude fat content of LT,and the ash content of BF were significantly lower than those of the confinement group(P<0.05),but the a*and b*of BF was significantly higher in the confinement group(P<0.05).Above results showed that the tenderness and color of pasture sheep was better than that of confinement sheep,but slaughter performance of pasture sheep was bad than that of confinement sheep.Muscle fibers characteristics were studied,the results showed that the expression of MyHC?and MyHC?x m RNA,the enzyme activities of MDH and SDH of LT and BF in the pasture group were significantly higher than those in the confinement group(P<0.05).In the pasture group,the muscle fiber density of LT,and the number ratio and area ratio of type IIA muscle fibers of the LT,and number ratio and area ratio of type I muscle fibers of BF were significantly higher than those in the confinement group(P<0.05).But,the LDH enzyme activity of LT and the number ratio of type?B muscle fibers of BF were significantly lower in the confinement group(P<0.05).The above results indicate that the pasture group increased proportion of oxidized muscle fibers,decreased proportion of glycolytic muscle fibers,and enhanced aerobic metabolism of muscles.Explore the reasons for the differences in muscle fiber characteristics of Sunit sheep under different feeding regimens,showed that the AMPK?2,Sirt1,MEF2C,COX?m RNA expression of LT and BF in pasture group were significantly higher than those in confinement group(P<0.05).TMT differential proteomics analysis shows that a total of123 differential proteins were identified of LT and BF in two feeding regimens,of which61 differential proteins were up-regulated and 62 differential proteins were down-regulated.In the pasture group,the expressions of MYL3,MYH7,TNNC1,TNNI1,and TNNT1 related to slow muscle fibers(oxidized muscle fibers)were significantly up-regulated;NDUFB8 and SDHB related to oxidative metabolism were significantly up-regulated;and ALDOB and ALDOC related to glycolytic metabolism significantly reduced.Ca N,which is related to the conversion of muscle fiber types,was significantly up-regulated in the Ca²⁺signaling pathway.The above test results show that feeding regimens mainly affect muscle metabolism through oxidative phosphorylation pathway,glycolysis/gluconeogenesis pathway,and functional characteristics such as muscle fiber structure and contraction through Ca²⁺signaling pathway,and Ca²⁺signaling pathway and AMPK signaling pathway affect the conversion of muscle fiber types.Research on the technology to improve the quality of Sunit sheep in confinement,the results showed that dietary linseed or lactic acid bacteria supplementation can increase the proportion of oxidized muscle fibers,enhance muscle aerobic metabolism,improve the meat tenderness in LT of confinement Sunit sheep.Increase the exercise amount of confinement Sunit sheep,which can increase the diameter and cross-sectional area of type I muscle fiber,reduce the meat color and tenderness and delay the rate of decrease in p H in LT.The above results indicate that dietary nutrition was more effective in changing muscle fiber properties and improving meat quality.The quality of confinement Sunit sheep can be improved by dietary linseed or lactic acid bacteria.