Effects Of Lactic Acid Bacteria On Mitochondrial Biogenesis,Muscle Fiber Characteristics And Meat Quality Of Sunit Sheep

In this study,a total of 24 Sunit sheep aged 3 months old were randomly divided into four groups,control group(C),1%lactic acid bacteria group(L1),2%lactic acid bacteria group(L2),3%Lactic acid bacteria group(L3).The effects of dietary supplementation with lactic acid bacteria on the muscle fiber characteristics,slaughter performance,carcass quality and meat quality of Sunit sheep were investigated by ATPase histochemical staining method and Real-time fluorescence quantitative PCR technology and Western blotting.The expression of key genes and proteins in the mitochondrial biogenetic pathway of skeletal muscle were determined to explain the differences in muscle fiber characteristics.The characteristics of muscle fiber of Sunit sheep were studied.The results showed that the number and area ratio of type?muscle fibers,the activities of MDH and SDH in the longissimus dorsi(LD)muscle of Sunit sheep in L1 group were significantly higher than those in group C(P<0.05),while My HC?b and My HC?x m RNA expression were significantly lower than those in group C(P<0.01).The muscle fiber density,the number ratio of type?muscle fiber,and My HC?a m RNA expression in biceps femoris(BF)muscle of Sunit sheep in L1 group were significantly higher than those in group C(P<0.05),while the number and area ratio,cross-sectional area of type?B muscle fiber,the diameter and cross-sectional area of type?muscle fibers,and the activity of LDH were significantly lower than those of group C(P<0.05).The diameter of type?B muscle fiber and the activity of SDH in the LD muscle of Sunit sheep in L2 group were significantly higher than those in group C(P<0.05).The muscle fiber density,cross-sectional area of type?B muscle fibers,and the activity of MDH in the BF muscle were significantly higher than those in group C(P<0.05),and the activity of LDH was significantly lower than those in group C(P<0.01).The cross-sectional area of type?muscle fiber,the diameter of type?and type?B muscle fiber,the activities of MDH and SDH in the LD muscle of Sunit sheep in L3 group were significantly higher than those in group C(P<0.05),while the area ratio of type?B muscle fiber was significantly lower than those in group C(P<0.05).The muscle fiber density,the cross-sectional area of type?B muscle fiber,the activity of MDH in the BF muscle were significantly higher than those in group C(P<0.05),while the activity of LDH was significantly lower than those in group C(P<0.05).The above results indicate that dietary supplementation with 1%lactic acid bacteria was beneficial to increase the proportion of oxidized muscle fibers and improve the oxidative metabolism capacity of the muscle.The slaughter performance,carcass quality and meat quality of Sunit sheep were studied.The eye muscle area of L1 group and the bone-meat ratio of L3 group were significantly higher than those in group C(P<0.05).Compared with group C,the cooking loss and ash content of the two parts of Sunit sheep in the L1,L2,and L3groups were significantly reduced(P<0.05).The p H₂₄value and intramuscular fat content of LD muscle,and b*value of BF muscle were significantly increased(P<0.05),while the shear force value and protein content of BF muscle in L1 group were significantly decreased(P<0.01).The p H₂₄value of LD muscle and the shear force value of two parts in L2 group were significantly increased(P<0.01).The p H₂₄value and shear force value of two parts in L3 group were significantly increased(P<0.01).Above results showed that dietary supplementation with 1%lactic acid bacteria has a positive effect on reducing the cooking loss,ash content,and increasing the p H value of meat.Skeletal muscle mitochondrial biogenesis of Sunit sheep was measured.It was found that dietary supplementation with 1%lactic acid bacteria significantly increased the gene expression of PGC-1?and the protein expression of p-AMPK,p-AMPK/AMPK,PGC-1?,COX?in the LD of Sunit sheep(P<0.05),and increased the gene expression of AMPK?1,SIRT1,PGC-1?,SIRT1,NRF-1,TFAM,COX?and the protein expression of p-AMPK,p-AMPK/AMPK,PGC-1?,TFAM,COX?in the BF(P<0.05),which promoted mitochondrial biogenesis.Based on the analysis of muscle fiber characteristics and the results of gene and protein expression determination,dietary supplementation with 1%lactic acid bacteria mediated AMPK/PGC-1?pathway to increase skeletal muscle mitochondrial biogenesis and promote the conversion of glycolytic muscle fibers to oxidized muscle fibers.