PSXI-23 - Effects of dietary threonine, tryptophan, and glycine supplementation on growth performance and intestinal barrier function in broiler chickens raised under multiple stress

Abstract: The objective of the current study was to compare the effects of dietary threonine, tryptophan, and glycine supplementation on growth performance and intestinal barrier function in broiler chickens raised under multiple stress. All birds were allotted to 1 of 5 treatments with 8 replicates in a completely randomized design. Positive control (PC) treatment was normal condition and other treatments are multiple stress condition with heat stress and high stocking density. Multiple stress condition was exposed to a cyclic heat stress condition (30 ± 0.3°C for 10 h/d and 23 ± 0.2°C for 14 h/d). In addition, 10 birds per cage (16.9 birds/m²) were allotted in multiple stress condition, but 15 birds per cage (25.3 birds/m²) were allotted in normal condition. Basal diet was fed to broiler chickens in PC (normal condition) and negative control (NC; multiple stress condition) treatments. Three additional diets were prepared by adding 0.68% threonine (99%), 0.19% tryptophan (99%), or 1.60% glycine (99%) to the basal diet. Four treatment diets such as NC, threonine, tryptophan, and glycine treatments were provided to birds in multiple stress condition. All experimental diets and water were provided ad libitum for 14 d. The body weight gain (BWG) and feed intake (FI) were recorded at the end of the experiment. The feed efficiency (FE, g/kg) was calculated by dividing BWG with FI after mortality correction for FI. The intestinal barrier function was analyzed by trans-epithelial electrical resistance (TEER) value in a two-channel Ussing chamber system. Statistical analysis was conducted as a completely randomized design by using the PROC MIXED procedure of SAS (SAS Institute Inc., Cary, NC). The replicate was considered an experimental unit. Outlier data were confirmed by the UNIVARIATE procedure of SAS. The LSMEANS procedure was conducted to calculate treatment means. In addition, if the difference was significant, the PDIFF option of SAS was conducted to separate the means. The significance for statistical tests was considered at P < 0.05. Results indicated that all treatments under multiple stress condition (i.e., NC, Thr, Trp, and Gly treatments) caused a significant reduction (P < 0.05) in BW, BWG, FI, and FE as compared to PC treatment. Dietary Thr supplementation under multiple stress condition was similar FE compared with PC treatment. Dietary threonine, tryptophan, and glycine supplementation under multiple stress condition induced intermediated values for TEER with dietary threonine supplementation having similar values to PC treatment. In conclusion, dietary supplementation of threonine seems the most effective functional amino acid. In addition, it can be a novel dietary treatment to improve growth performance and gut health in broiler chickens raised under multiple stress condition.