Effects Of Dietary Threonine On Growth Performance,Carcass Trait And Immunity Function Of Peking Ducks From Hatch To 21 Days

Threonine(Thr)is one of the four main limiting amino acids of poultry,and it plays a very important role on the poultry's maintenance of normal growth,development and immune function.Although there have been very comprehensive studies on the mechanism of broilers and laying hens over the past ten years,there were still relatively fewer studies on ducks.A study was concudcted to evaluate the effect of diertary threonine levels on growth performance,carcass trait,blood metabolites in serum and immunity performance of 0~21d Peking ducklings,to determinethe optimum threonine level for 0~21d Peking ducklings.Experiment 1: This experiment was conducted to investigate the effects of different dietary Threonine levels on the growth performance,carcass traits,immune function and serum hormone of Peking ducklings.A total of 320 Peking ducklings were randomly assigned to a 5 factorial arrangement of treatments.Each treatment group consisted of 8 replicate pens with 8 ducks per pen.Control group was fed with basal diet and experiment groups were fed with experiment diets which were mixed with Thr addictive.Threonine levels of 5 diets were 0.60%?0.68%?0.76%?0.84%?0.92%(0.65%?0.69%?0.81%?0.88%?0.98% on an analyzed basis).The experiment lasted for 21 days.The results showed as following: 1)diet Thr level had significant effect on duckling's average feed intake and body weight gain(BW gain)(P<0.05).2)Addition of Thr improved breast meat rate of ducklings significantly(P<0.05).3)Addition of Thr in diet increased ducklings' Bursary of Fabricius weight and Average Thymus weight significantly(P<0.05).4)Diet Thr level improved the concentration of T3 in duckling's serum(P<0.05).5)The effects of Thr requirements on BW gian,feed intake and breast meat rate were all quadratic.According to the conic section model,the threonine requirements were 0.86%?0.85%?0.84%,respectively.The results suggest that supplementing the diet with suitable Threonine level can improve duckling's growth performance,carcass performance and immune performance.Experiment: This experiment was conducted to investigate the effects of different dietary Threonine(Thr)levels and immune stress of Peking ducklings based on the growth performance,carcass traits,serum immune parameters and intestinal mucin 2(MUC2)and NF-?b gene expressions.A total of 320 Peking ducklings were randomly assigned to a 5×2 factorial arrangement of treatments.Each treatment group consisted of four replicate pens with eight ducks per pen.Ducklings were fed five graded levels of Thr: 0.49%,0.56%,0.60%,0.65%,0.76% from hatch to day 21 of age.On day 11,ducks in stressed groups were challenged with Bell Serum Albumin(BSA),and ducks in the unstressed groups were injected with normal saline water.In this experiment Body weight and feed intake from each pen were recorded weekly.At 17 d and 21 d of age,blood serums were collected to determine serum immunological parameters.At 22 d of age,breast meat,leg meat,intestinal tissue and immune organs were collected to determine breast meat yield,leg meat yield,immune organ weights,mucin 2(MUC2)and NF-?B gene expression.The results showed that 1)increasing Thr supplementation from 0.49% to 0.56% in diet can improve 21 d Peking ducklings' BW gain,feed intake,weight and relative weight of breast and leg,weight of liver,bursa of fabricius,spleen,thymus,serum natural IgA concentration and MUC2 gene expression in ileum significantly.2)Immune stress with BSA had significant effect on 21 d Peking ducklings' BW gain,feed intake,weight and relative weight of breast and thymus,but no interaction between BSA and dietary Thr content was noticed in our experiment.Therefore,increasing dietary Thr concentration can improve 0~21d Peking duck's growth performance,carcass trait and immunity function,and xiaochang can also effect the concentration of relative indicators in serum and the gene expression in intestine.