Study On The Effects Of Dietary Supplementation With Carnosine On Growth Performance,Meat Quality And Its Regulation Mechanisms In Broiler Chickens

Body oxidation equilibrium state plays an important role in the normal growth of poultry.However,poultry were affected by external environment factors,feeding management,transport and slaughter,which lead to the production and accumulation of reactive oxygen species.These make the oxidation-antioxidation mechanism of body imbalance,and finally,induce oxidative stress and low meat quality.In addition,muscle fibers,as muscle composition unit,play a decisive role in meat quality.Now,a large number of studies have confirmed that the addition of exogenous antioxidant substances is of great significance to improve antioxidant capacity,muscle fiber characteristics,meat quality and animal health.Carnosine has been found to inhibit protein and lipid oxidation by chelating metal ions and scavenging free radicals.Therefore,in the research,the purpose was to conduct the effect of carnosine(a natural antioxidant)on the growth performance,carcass traits,meat quality,antioxidant property and muscle fiber characteristics of broiler chickens,and explore the mechanism of carnosine on meat quality,thus providing a theoretical reference for the rational use of carnosine in broiler industry.1.Effects of dietary supplementation with carnosine on growth performance,carcass characteristics and meat quality in broiler chickensA total of 256 one-day-old male Arbor Acres broilers were randomly assigened to 4 treatments,with 8 replicates per treatment and 8 chickens per replicate.The four groups were fed basal diets supplemented with 0,100,200 or 400 mg/kg carnosine,respectively.The whole experiment lasted for 42 days.The results showed as follows:compared with the control group,1)dietary supplementation with carnosine increased carnosine content in breast muscle at 21 and 42 days of age,but only increased that of thigh muscle at 42 days of age(P<0.05);2)in the starter phase,the feed:gain was decreased in all carsnosine group(linear,P=0.017),however,no significant differences in average feed intake and body weight gain in each period were found(P>0.05),in the high carnosine group,half-eviscerated yield(linear,P=0.002)and leg muscle yield were increased significantly(linear,P=0.004);3)carnsine addition resulted in increases in pH45min and redness and decrease in drip loss in both breast and thigh muscle,meanwhile,dietary carnosine also enhanced cohesiveness,reduced cooking loss,shear force and hardness of thigh muscle(linear,P<0.05).These results indicated that:dietary supplementation with carnosine could improve the growth performance,carcass characteristics and meat quality of broiler chickens.2.Effects of dietary supplementation with carnosine on antioxidant capacity in broiler chickensExperiment design was the same with experiment 1.The results showed as follows:compared with the control group,1)dietary supplementation with carnosine elevated the activities of antioxidant enzymes in serum,liver,breast and thigh muscle at 21 and 42 days of age(linear,P<0.05);2)in high carnosine groups,carbonyl content in breast muscle was significantly decreased at 21 and 42 days of age,but the carbonyl cantent in thigh muscle was only decreased at 42 days of age(P<0.05);3)dietary carnosine reduced the contents of MDA(linear,P=0.004),LPO(linear,P=0.010)and 4-HNE(linear,P=0.004)in breast muscle,MDA(linear,P=0.008)and 4-HNE(linear,P=0.003)in thigh muscle at 21 days of age,4-HNE(linear,P=0.002)in breast muscle,MDA(linear,P=0.009)and LPO(linear,P=0.014)in thigh muscle at 42 days of ages(P<0.05).The results indicated that:dietary supplementation with carnosine could elevated the activities of antioxidant enzymes,reduced the accumulations of advanced oxidation protein products and advanced lipoxidation end-products.3.Effects of dietary supplementation with carnosine on muscle fiber characteristics and the expressions of Calcineurin signaling pathway related genesExperiment design was the same with experiment 1,The results showed as follows:compared with the control group,1)dietary supplementation with carnosine decreased the diameters and increased densities of muscle fibers in breast and thigh muscle at 21 and 42 days of age(linear,P<0.001);2)the ratios of ?a fibers were increased whereas ?b fibers were decreased in thigh muscle at 21 days of age(linear,P<0.001),similarly,the ratios of ?fibers(linear,P=0.008)and ?a fibers(linear,P<0.001)were increased,?b fibers(linear,P<0.001)were decreased at 42 days of age;3)carnosine addition up-regulated the mRNA expressions of CaN,NFATc1 and PGC1a in thigh muscle at both 21 days and 42 days of age(linear,P<0.05),meanwhile,the expressions of CaM at 21 days of age,MEF2C and Myf5 at 42 days of age were also up-regulated(linear,P<0.05).The results indicated that:dietary supplementation with carnosine could decrease diameters and increase densities of muscle fiber,promote the transformation of thigh muscle fibers from type ?b to type ? and?a.The variations in fiber type might be related to the changes in the expressions of genes correlated with calcineurin-NFATc1.