Effect Of Taurine On The Performance And Antioxidative Capacity Of Chicken

Taurine is one of the most abundant free amino acids in the body.Taurine plays a role in the anti-inflammatory,redox balance,osmotic pressure,and glucose metabolism.Biologically,endogenous taurine is synthesized from methionine,and taurine can react with bile acid to form conjugated bile acids.Therefore,we studied the effects of methionine replacement with taurine,supplementation with taurine and bile acid on the growth,egg laying performance and antioxidant capacity in broilers and laying hens.The in vitro cultured chicken primary hepatocytes,intestinal epithelial cells and myoblasts were further employed to investigated the effect of taurine on the antioxidant capacity and glucose uptake.Experiment 1: By using broilers as a model,the effect of replacement of crystallized methionine with taurine on growth performance was investigated.A total of 256 1-day-old AA broilers with similar body weight were randomly divided into four groups,and subjected to the following treatments: fed with basal diet supplemented with 0.21%(0-3 w)/0.14%(4-6 w)crystallized Met(CON),the basal diet and replace 15%(15TAU),30%(30TAU),45%(45TAU)of crystallized Met with taurine.The average daily body weight gain,feed intake,and feed efficiency of broilers were not influenced(P>0.05)by dietary in the period of 1-21,22-42,and1-42 day of age.Compared with the CON group,the MDA content in the liver of 15 TAU group and 45 TAU group decreased(P<0.05);in the thigh muscle,the MDA content of the 15 TAU group decreased(P<0.05),and the MDA content of the 45 TAU group showed a trend to be decreased(P=0.07);the CAT activity of liver and the SOD,CAT,GSH-Px activities of thigh muscle were decreased(P<0.05)in taurine treatment group compared with the CON group.Glucose tolerance test results showed that intraperitoneal taurine injection(0.2 and 0.6g/kg body weight)before oral glucose intake(2g/kg body weight)significantly decreased(P<0.05)the serum glucose level of broilers compared with the CON group.The results indicated that taurine changes the redox state of broiler tissues and participates in glucose metabolism.Experiment 2: Effects of replacement of crystallized methionine with taurine on laying hens.A total of 288 40-week-old Isa brown laying hens with similar body weight and laying rate were divided into 4 groups and subjected to the following treatments: fed with basal diet supplemented with 0.17% crystallized Met(CON),the basal diet and replace 25%(25TAU),50%(50TAU)of crystallized Met with taurine,the CON diet supplemented with 0.1% taurine(0.1% TAU).The laying rate of the 50 TAU group was higher(P<0.05)than the CON group,and the average feed intake,egg weight,feed efficiency of laying hens were not influenced(P>0.05).Compared with the CON group,in the liver,the MDA content in the 50 TAU group showed a trend to be decreased(P=0.09);the SOD activity in the 50 TAU group and 0.1%TAU group decreased(P<0.05);the protein expression of Nrf2 in the 0.1%TAU group showed trend to be increased(P=0.09);in the duodenum,the SOD activity in the 0.1%TAU group decreased(P<0.05),and there was a trend to be reduced of the SOD activity(P=0.05)in the 50 TAU group and the MDA content(P=0.07)in the 0.1%TAU group;the duodenal weight in the 25 TAU group significantly decreased(P<0.05),the 50 TAU group and 0.1%TAU group showed a trend to be decreased(P=0.08),the duodenal villus height and jejunal weight decreased(P<0.05)in the 50 TAU group and 0.1%TAU group.The results indicated that taurine changes the redox state of liver through the Nrf2 pathway and affects the intestine in laying hens.Experiment 3: Effects of the taurine and bile acids on broilers.A total of 420 1-day-old AA broilers with similar body weight were randomly divided into four groups and subjected to the following treatments: fed with basal diet supplemented with 0.13%(0-3 w)/0.07%(4-6 w)crystallized Met(CON),the CON diet+60 mg/kg bile acids(BA+MET),basal diet+60 mg/kg bile acids(BA,no methionine),the CON diet and replace all of crystallized Met with taurine+60mg/kg bile acids(BA-TAU).The average body weight gain,feed intake,and feed efficiency of broilers were not influenced(P>0.05)in the period of 1-21 day of age;at the age of 22-42 days,the average body weight gain showed a trend to be increased(P=0.05)in the BA-MET group;the average body weight gain significantly decreased(P<0.05)in the BA group compared with the CON group in the period of 22-42,1-42 day of age,and the feed intake tended to increased(P=0.07)in the BA-MET group at the age of 1-42 days;there was a trend to be decreased(P=0.07)in the BA-MET group and significantly decreased(P<0.05)in the BA group and BATAU group of abdominal fat ratio.The results indicated that bile acids could enhance the growth performance of broilers to a certain extent,and the lack of methionine induced negative impacts on the performance.The effect of combining bile acids and taurine can compensate for the adverse effects caused by methionine deficiency in the diet.Experiment 4: Effects of taurine on the antioxidative capacity of chicken primary hepatocytes,intestinal epithelial cells and glucose uptake of chicken primary hepatocytes,myoblasts.The effects of taurine treatment(0,1,5,10 m M)on glucose uptake and antioxidant capacity of cells were studied by culturing chicken primary hepatocytes,intestinal epithelial cells and myoblasts in vitro.In the hepatocytes,the MDA,GSH content,and CAT,GSH-Px activity,and the protein expression of Nrf2 decreased(P<0.05)of the taurine treatment group,while the SOD activity increased(P<0.05);in the 10 m M taurine treatment group,the m RNA expression of SOD1,SOD2,CAT,GCLC were increased(P<0.05)and GSR were decreased(P<0.05).In the intestinal epithelial cells,SOD activity decreased(P<0.05)and CAT activity increased of the 10 m M taurine treatment group(P<0.05).MDA,GSH content and GSH-Px activity were not influenced(P>0.05).The m RNA and protein expression of Nrf2 in the 10 m M taurine treatment group was decreased(P<0.05),and other m RNA expression levels were not influenced(P>0.05).The glucose uptake of hepatocytes and myoblasts in the taurine treatment group increased(P>0.05).These results indicated that taurine changes the redox state of chicken primary hepatocytes and intestinal epithelial cells through the Nrf2 pathway,and participates in glucose metabolism via the glucose uptake of chicken primary hepatocytes and myoblasts.In summary,replacement 15%,30%,45% of crystallized Met with taurine did not significantly change the growth performance of broilers,replacement 25%,50% of crystallized Met with taurine did not significantly change the performance of laying hens,indicated that taurine could replace partially Met in the diet.The effect of bile acid and taurine can compensate for the adverse effects in growth performance caused by the lack of Met.Taurine regulates the blood glucose level of broilers by enhancing the uptake of glucose in the hepatocytes and myoblasts,meanwhile changes the redox state in the liver of broilers and laying hens through the Keap1/Nrf2 pathway.