Work

Balanced corrections of branched-chain amino acids and tryptophan in corn and soybean meal-based turkey starter diets with excess leucine restores d14 performance and d28 blood plasma serotonin concentration and enhances d28 performance and tibia mineralization

Year: 2026

Type: article

Abstract: Large inclusions of concentrated corn proteins in commercial poultry diets can increase leucine levels above requirement, leading to antagonisms among limiting branched-chain amino acids (BCAA). Excess leucine may also inhibit tryptophan metabolism. High-leucine diets can be corrected with crystalline amino acids to prevent imbalanced BCAA/tryptophan ratios. This study evaluated the effects of varying dietary BCAA/tryptophan ratios using corn gluten meal, L-valine, L-isoleucine, and L-tryptophan on performance, plasma serotonin concentration, immune organ weight, and tibia mineralization in turkey poults from 0-28 days. A corn and soybean meal-based diet served as the Control. Uncorrected, high-leucine diets (1.6 leucine:lysine) reduced feed intake (FI), bird weight (BW), and live weight gain (LWG) relative to the Control at d14 (P<0.05). Fully-corrected high-leucine diets with additions of L-valine, L-isoleucine, and L-tryptophan produced equivalent FI and increased BW and LWG relative to the Control at d14, 21, and 28 (P<0.05). Serotonin concentrations were lower in the uncorrected, high-leucine diet and isoleucine-corrected diet than the Control (P<0.05). Spleen weight was lower and tibia ash was higher in poults fed the fully-corrected high-leucine diets than the Control (P<0.05). These results suggest that performance reductions from excess leucine may be most significant at d14, although high-leucine diets with corrections of L-valine, L-isoleucine, and L-tryptophan can maintain or enhance performance compared to a corn-soy control throughout a 28d starter phase in turkeys. Nutritionists should consider the economic and performance costs associated with higher inclusion levels of these feed-grade amino acids and concentrated corn proteins.

Source: The Journal of Applied Poultry Research

DOI: 10.1016/j.japr.2026.100739