Effects And Mechanisms Of Dietary Supplementation With Taurine On Growth And Meat Quality Of Broiler Chickens

The development of large-scale and intensive meat production has greatly improved the performance of livestock and poultry,while also results in some issues that the heterogenous meat occurrence rate enhancement and the meat quality decline.In recent years,many studies have shown that the type of muscle fiber and redox state are the key factors affecting the formation of meat quality.Taurine,a ubiquitous sulfur-containingβ-amino acid,exists in all tissues of mammals.Taurine was reported to play an important role in regulating the concentration of calcium ions,maintaining osmotic pressure balance and improving the antioxidant capacity of the body.Therefore,taurine was added to the diets of Arbor Acres(AA)broilers to study the effects of taurine on the growth performance,slaughtering performance,meat quality,antioxidant performance,glycolysis characteristics and muscle fiber characteristics of broilers,and exploring the mechanism of taurine on meat quality in broilers.1.Effects of taurine supplementation on growth performance,slaughter performance and meat quality in broiler chickensIn this experiment,a total of 72 male Arbor Acres broiler chickens(28-day-old)were randomly allocated into two groups,with six cages per group and six birds per cage.The control chickens were fed with a basal diet.The chickens in the taurine group were fed with the basal diet supplemented with 0.5%taurine.The trial lasted for 14 d.The results are shown bellow:relative to the control group,1)dietary taurine supplementation had no effect on average daily feed intake,average daily gain and feed/gain ratio in broilers(P>0.05).2)Dietary taurine supplementation had no significant effects on carcass yield,eviscerated yield,breast muscle yield,leg muscle yield and abdominal fat yield,(P>0.05).3)Dietary taurine supplementation significantly increased pH24h and markedly decreased drip loss and cooking loss in breast muscle.Meanwhile,supplementation of taurine greatly increased pH45min and pH24h,while significantly reduced shear force and cooking loss in thigh muscle(P<0.05).Taurine supplementation had no effect on the moisture,crude fat and crude protein content of the regular chemical composition in breast muscle(P>0.05).However,supplementation of taurine greatly increased the moisture content in thigh muscle(P<0.05).The results suggested that dietary taurine supplementation had no effect on the growth performance and slaughter performance in broilers,while significantly improved the meat quality of breast and thigh muscle.2.Effects of taurine supplementation on antioxidative capacity and Nrf2-ARE pathway in broiler chickensThe experiment design was the same as experiment 1.The results showed as follows:compared with the control group,1)dietary taurine supplementation significantly increased the scavenging activities of superoxide radical(O2-)and 2,2-diphenyl-1-picrylhydrazyl(DPPH·)in breast muscle,and significantly increased the scavenging activities of hydroxyl radical(OH·),O2-and DPPH-in thigh muscle(P<0.05).2)Dietary taurine supplementation significantly increased the content of total mercapto(-SH)while significantly decreased the contents of Carbonyl,malondialdehyde(MDA),lipid peroxide(LPO),4-hydroxynonenal(4-HNE),and 8-hydroxydeoxyguanosine(8-OhdG)in breast and thigh muscle(P<0.05).3)Dietary taurine supplementation significantly increased the activities of superoxide dismutase(SOD)and total antioxidant capacity(T-AOC)in serum,and obviously elevated the activities of SOD,T-AOC,glutathione peroxidase(GSH-Px),and catalase(CAT)in liver(P<0.05).Meanwhile,broilers in the taurine group exhibited significantly higher activities of SOD and T-AOC in breast muscle,and significantly higher activities of T-AOC and GSH-Px in thigh muscle(P<0.05).4)Taurine supplementation significantly upregulated the mRNA expression of Nrf2,HO-1,NQO1,SOD,CAT,GSH-Px,γ-GCLc,and γ-GCLm in breast muscle,and significantly upregulated the mRNA expression of Nrf2,HO-1,NQO1,SOD,GSH-Px,and γ-GCLc in thigh muscle(P<0.05).The results suggested that dietary taurine supplementation plays an antioxidant role in improving the antioxidant enzyme activities of the body,enhancing the scavenging ability of free radicals,and then reducing the oxidation products via activating Nrf2-ARE pathway.3.Effects of taurine supplementation on glycolysis characteristics,muscle fiber characteristics and CaN-NFAT pathway in broiler chickensThe experiment design was the same as experiment 1.The results showed as follows:compared with the control group,1)dietary taurine supplementation significantly reduced glycolytic potential(GP)in breast muscle,and significantly decreased the content of lactate and GP in thigh muscle(P<0.05).Meanwhile,broilers in the taurine group exhibited significantly higher activities of lactate dehydrogenase(LDH)and pyruvate kinase(PK)in breast and thigh muscle(P<0.05).2)Taurine supplementation markedly reduced the diameters and evidently rised densities of muscle fibers in breast and thigh muscle(P<0.05).3)Taurine supplementation significantly increased the ratios of I fibers,whereas decreased the ratios of Ⅱb fibers in thigh muscle(P<0.05).4)Taurine supplementation significantly upregulated the mRNA expression of CaN,NFATc1,MEF2C,and PGC1α in thigh muscle(P<0.05).The results suggested that dietary taurine supplementation promoted the transformation of thigh muscle fibers from type Ⅱb to type Ⅰ,and decreased GP via activating the CaN-NFAT pathway.In conlusion:dietary 0.5%taurine supplementation had no effect on the growth performance and slaughter performance in broiler.However,taurine supplementation enhanced antioxidative capacity of the body,and promoted the transformation of thigh muscle fibers from type Ⅱb to type Ⅰ,and then improved the meat quality via activating the Nrf2-ARE and CaN-NFAT pathway.