Effects Of Feeding Regimens On Muscle Fiber Characteristics And Meat Quality Of Sunit Sheep

This study was conducted to investigate the effects of different feeding regimens on muscle fiber characteristics,slaughter performance,carcass characteristics and meat quality of Sunit sheep by ATPase histochemical staining method,Real-time fluorescence quantitative PCR technology(QPCR)and Enzyme-linked immunosorbent assay(ELISA).Then effects of dietary linseed supplementation on muscle fiber characteristics and meat quality were detected in captive sheep.The mechanism of muscle fiber conversion was also studied.It provides theoretical basis and data support for improving mutton quality by regulating dietary nutrition in the future.The effects of feeding regimens on muscle fiber characteristics were investigated by ATPase staining and the genes expression of MyHC isoforms.The result showed that compared with captive(C1)group,the proportion of oxidative fibers(type Ⅰ and type Ⅱ A)was higher in pasture(P)group,while the proportion of glycolytic fibers was lower.The diameter of Longissimus dorsi muscle(LD)fibers in the P group was significantly lower than that in the C1 group(P<0.01),the order of diameter of three type muscle fibers were type ⅡB<type Ⅰ<typeⅡA in LD and BF.The carcass width and bone-to-meat ratio of P group were higher than those of C1 group(P<0.05);The net meat weight,meat production rate,slaughter rate and net meat ratio of C1 group were higher than those of P group(P<0.05).In terms of meat quality,the a*value in the P group was significantly higher(P<0.05),whereas the L*value、pH24 and shear force value were significantly lower than those in C1 group(P<0.05).Correlation analysis showed that the meat quality is closely related to muscle fiber characteristics.Regulating the muscle fiber characteristics through dietary linseed supplementation,the result showed that dietary linseed supplementation increased the proportion of type I muscle fibers in Sunit sheep(P<0.05).Meanwhile,the expression of MyHC Ⅰ,MyHC Ⅱ a and MyHC Ⅱ x genes were all up-regulated(P<0.05).The diameter of LD fibers in the linseed(L)group was significantly lower than that in the control(C2)group(P<0.01),and the oxidative metabolism ability of muscle was significantly improved(P<0.05).The above results revealed that the muscle fiber type transformation from glycolytic fibers to oxidative fibers by dietary linseed supplementation.Dietary linseed supplementation dose do not adversely affect the slaughter performance and carcass characteristics of Sunit sheep,but actively improve mutton quality.The L*,pH24 and shear force value of Sunit sheep were significantly reduced(P<0.05),conversely,the a*and b*of BF were significantly lower in L group(P<0.05).And the moisture and ash content of the LD in the L group were greater than those in the C2 group(P<0.05).The mechanism of dietary linseed supplementation effects on muscle fiber characteristics were studied.It was found that the gene expression of COX IV of the BF in the L group was up-regulates,and the gene expression of CPT1 was up-regulates in L group between the LD and BF.The expression level of PGC-la of the BF in the L group was higher than that in the C2 group(P<0.05),and the expression level of PPARβ of LD was higher than that in the C2 group(P<0,01).The regulation of muscle fiber type by dietary linseed supplementation may be due to the activation of PPARβ via unsaturated fatty acids in linseed.PPARβ/PGC-1α promotes conversion of muscle fiber types from glycolytic to oxidative through enhanced mitochondrial respiration and fatty acid oxidation.