Limiting amino acid responses in commercial broilers

A level of dietary crude protein (CP) is usually specified in least cost fo rmulation for commercial broilers. A better understanding of less limiting amino acid needs (i.e., threonine, isoleucine,and valine) may allow nutriti onists to better understand the minimum level of CP needed, thereby minimiz ing marginal excesses of the less limiting amino acids. The efficiency of p oultry production decreases during periods of hot weather conditions, and t he impact of environmental temperature on the less limiting amino acids is poorly understood. The interactive effects of dietary lysine, threonine, an d the branched-chain amino acids (BCAA) were evaluate in two experiments in growing broilers reared in thermoneutral and hot temperature conditions. E xperiment 1 was conducted in hot temperature conditions and indicated that threonine needs of growing and finishing broilers to optimize feed conversi on may be affected by the starter level of dietary lysine. In addition, som e amino acid treatments decreased hot temperature-related mortality of broi lers indicting the need for amino acid-balanced diets in periods of hot tem perature conditions. An isoleucine response occurred in breast meat yield i n Experiment 2 indicating the importance of meeting an isoleucine minimum i n dietary formulation for growing broilers.