Effect Of Dietary L-histidine And ?-alanine On Growth Performance,Meat Quality And Muscle-derived Active Peptide In Broiler Chicks

Imidazole dipeptide?carnosine or anserine?is a functional dipeptide who is synthesized from L-histidine and?-alanine by means of carnosine synthetase,exits muscle and brain.It plays an important role in maintaining pH stability,antioxidation,anti-aging and neuromodulation.With the living standard of residents and the increasing attention of health,the meat products containing functional peptide are increasingly favored by consumers.In this study,the effects of different levels of L-histidine and?-alanine on the production performance,meat quality and peptides in muscle were studied to determine the suitable combination of L-histidine and?-alanine,in addition,the mechanism of L-histidine and beta-alanine in regulating the production of active peptide of broiler muscle was preliminarily discussed from the aspects of the expression of dipeptide synthesis and catabolism.This study is divided into three parts:Experiment 1:Effect of Low Dose L-histidine on The Production Performance and Slaughter Performance of Broiler ChicksIt was reported that dietary supplementation with L-histidine could reduce the production performance of broilers.This experiment was conducted to study the supplementation of L-histidine on growth performance and slaughter performance of broilers.A total of 240 one-day-old male Arbor Acres?AA?broilers were randomly allotted into 4 groups with 6 replicates of 10 chickens each.The control group was fed a basal diet,the experimental groups were fed the basal diet supplemented with250,500,1000 mg/kg L-histidine,respectively.The trial lasted for 42 days.The results showed as follows:1)Dietary supplemental L-histidine significantly increased the weight of body and the average daily gain at 21 d?P<0.05?,there was no significant effect on BW and ADG at 42 d?P>0.05?.2)Compared with the control group,the addition of L-histidine had no significantly effect on dressing percentage,breast muscle percentage,leg muscle percentage and abdominal fat percentage?P>0.05?.To sum up,the addition of low-dose L-histidine could increase the ADG and BW in starting period,which had no significant effect on growth performance in fatting period and the slaughtering performance.Experiment 2:Effect of L-histidine on Growth Performance,Meat Quality,Antioxidant Ability and Imidazole Dipeptide of Broiler ChicksThis experiment was conducted to study the supplementation of L-histidine on growth performance,meat quality,plasma antioxidant ability and imidazole dipeptide content in breast muscle of broilers.A total of 300 one-day-old male Arbor Acres?AA?broilers were randomly allotted into 5 groups with 6 replicates of 10 chickens each.The control group was fed a basal diet,the experimental groups were fed the basal diet supplemented with 250,500,1000,2000 mg/kg L-histidine,respectively.The trial lasted for 42 days.The results showed as follows:1)The feed conversion rate was significantly higher in 250 and 2000 mg/kg groups than the control at the grower phase?22 to 42 days of age??P<0.05?.2)Dietary L-histidine supplementation had no significant effect on carcass yield,the drip loss,shear force and pH of the breast muscle?P>0.05?.3)At 42 days of age,the total antioxidant capacity,the activities of the glutathione peroxidase and superoxide dismutase in the plasma were increased linearly with the supplemental levels of L-histidine in the diets?P<0.01?.4)At 42 days of age,the content of carnosine and anserine of breast muscle were significantly increased with L-histidine supplementation?P<0.01?.The optimal level of L-histidine was1276 mg/kg according to the fitted formula in the current study.In conclusion,dietary L-histidine supplementation could promote the growth performance,improve plasma antioxidant ability and increase the content of imidazole dipeptide of the breast muscle in broilers,and the optimal level of L-histidine is 1000²000 mg/kg in the current study.Experiment 3:Effects of Dietary Supplementation of L-histidine and?-alanine on Growth Performance,Breast Muscle Carnosine Content and Carnosine-related Enzyme mRNA Expression in Broiler ChicksThe current study was performed to investigate the effects of dietary addition of L-histidine and?-alanine on growth performance,breast carnosine content and carnosine-related enzyme mRNA expression in broiler chicks.A total of 640 1-day-old male broiler chicks were assigned into 8treatments with factorial arrangement containing 4 level of L-histidine supplementation?0,650,1300 or 1950 mg/kg?and 2 levels of?-alanine?0 or 1200 mg/kg?.Each treatments consisted of 8replicates with 10 birds each.The results showed that dietary L-histidine,?-alanine and their interaction did not affect the growth performance?P>0.05?.Interaction between histidine and?-alanine existed on meat color?P<0.05?.Dietary supplementation of 1300 mg/kg histidine+1200mg/kg?-alanine had the lowest b*_{24 h} value.Dietary L-histidine at 1300 or 1950 mg/kg level had higher pH_{24 h} compared with the exogenous L-histidine free control?P<0.05?.In breast muscle,both dietary histidine and?-alanine elevated the total antioxidant capacity and glutathione peroxidase activity and decreased malondialdehyde content,and dietary histidine additionally increased the total superoxide dismutase activity?P<0.05?.The combination of 1300 mg/kg L-histidine and 1200 mg/kg?-alanine had the superior muscle antioxidant ability.Muscle carnosine content were increased by L-histidine,?-alanine and their interaction?P<0.05?.The group of 1300 mg/kg L-histidine plus 1200mg/kg?-alanine had the highest carnosine and anserine content in breast muscle.Both L-histidine and?-alanine supplementation significantly elevated carnosine synthase mRNA expression,and L-histidine further increased the expression of transporter of carnosine/L-histidine and L-histidine decarboxylase mRNAs?P<0.01?.In conclusion,dietary addition of L-histidine and?-alanine increased antioxidant capacity,and increased meat derived imidazole dipeptide contents through the upregulation of gene expression of carnosine synthesis related enzymes.The combination of 1300 mg/kg L-histidine and 1200 mg/kg?-alanine may gain the satisfactory imidazole dipeptide contents in breast muscle of broilers.