الفهرس 
Introduction
Biochemical Aspects of ThreonineOnly 14 pages are availabe for public view
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Abstract
Babcock Brown layers (و40 wk of age, were allocated to 5 dietary treatments groups, each of which included 6 replicates of 32 hens. Each group received the same basal diet formulated with corn, peanut meal, and crystalline amino acids. L-Threonine was added to the basal diet at 0 (control), 0.1, 0.2, 0.3, and 0.4 % for 8 wk. Chemical analysis of the diets for threonine values are 0.48,0.58, 0.66, 0.74, and 0.85 %, respectively. Our findings showed that egg production response to supplemental L-threonine was quadratic, and it was maximized at 0.2% supplemental l-threonine. Serum total protein concentration increased quadratically to supplemental threonine, and the response was maximized at 0.2 and 0.3% supplemental l-threonine. Serum free threonine increased quadratically as supplemental threonine increased, and the response was maximized between 0.2 and 0.3% supplemental l-threonine. The addition of l-threonine at 0.3% resulted in linearly increasing levels of IgG and total Ig (P < 0.05) as compared with those of the control group. The numbers of goblet cells did not change due to L-threonine supplementation at 0.2 or 0.3% as compared with control group. Also, L-threonine had no affect on the villus height and mucosal thickness at 0.2 or 0.3% L-threonine. L-threonine supplementation at 0.2% increased the level of serum SOD (0.05). Expressions of jejunal and ileal mucin 2 mRNA were increased linearly by increasing l-threonine 0.01). At 0.4% l-threonine, the concentrations of IgA antibody in the mucosa of the ileum increased linearly 0.01). It was concluded that dietary threonine requirements as reported in current NRC (1994) recommendations are insufficient for modern commercial laying hens raised in summer climates.