The Requirement Of Dietary Threonine In Broilers During 0 To 6 Weeks

This aim of this experiment was to investigate the effect of different dietary threonine levels on the growth performance, carcass traits, physiological and biochemical parameters and immune function in broilers. The purpose was to estimate the optimum requirements for dietary threonine in broilers at 0 to 3 weeks and 4 to 6 weeks. Three hundred and sixty one-day aged AA broilers were randomly allocated to 5 dietary treatments with 6 replicates of 12 male chicks. Diets Thr were formulated on basis of digestible amino acids. Threonine levels of maize-soybean-peanut meal basal diet were 0.53%(the basal diet), 0.60%, 0.67%, 0.70%, 0.73% at 0 to 3 weeks; 0.49%(the basal diet),0.55%,0.61%,0.64%和0.67% at 4 to 6 weeks, respectively. The results showed that: 1. On the base of this study, the standard ileal digestibility of threonine were 80.74%at 0 to 3 weeks and 77.55% at 4 to 6 weeks. The calculated value of standard digestible theronine of the basal diet were 80.74% and 77.55% during 0~3 weeks and 4~6 weeks respectively. 2. ADG and F/D were significantly effected by the dietary threonine levels. The Thr requirement was 0.61% for ADG and F/G at 0 to 3 weeks and 0.61% at 4 to 6 weeks, and the level of Thr was from 0.61% to 0.64% for carcass traits. It can be received from data that the need of Thr for optimized carcass traits was higher than that of optimized growth performance. 3. From the analysis of serum biochemical indexs, serum hormone indexs and serum fat parameters, the optinum dietary threonine levels for broilers were 0.60%~0.67% at 0 to 3 weeks and 0.61%~0.64% at 4 to 6 weeks. 4. Addition of Thr developed the immune organ, improve the immune function of broilers. To be concluded from comparation of the immune response indexs and growth performance parameters that the need for dietary threonine to optimize immune function was higher than that of optimum growth performance during 0-3 weeks and 4 -6 weeks 5. The Model of Quadratic Function was used to estimate Thr requirements of chicks. The estimation of theronine need developed by growth performance was 0.641% during 0 to 3 weeks and 0.651% during 4 to 6 weeks. The dietary threonine requirement estimated with feed/gain were 0.635% at 0 to 3 weeks and 0.592% at 4 to 6 weeks. The Thr need developed by eviscerated carcass weight rate, breast meal rate, thigh meat rate and abdominal fat were 0.592%, 0.642, 0.614% and 0.623%, respectively.