Limiting Amino Acid Responses in Commercial Broilers

A level of dietary crude protein (CP) is usually specified in least cost formulation for commercial broilers. A better understanding of less limiting amino acid needs (i.e., threonine, isoleucine, and valine) may allow nutritionists to better understand the minimum levels of CP needed, thereby minimizing marginal excesses of the less limiting amino acids. The efficiency of poultry production decreases during periods of hot weather conditions, and the impact of environmental temperature on the less limiting amino acids is poorly understood. The interactive effects of dietary lysine, threonine, and the branched-chain amino acids (BCAA) were evaluated in two experiments in growing broilers reared in thermoneutral and hot temperature conditions. Experiment 1 was conducted in hot temperature conditions and indicated that threonine needs of growing and finishing broilers to optimize feed conversion may be affected by the starter level of dietary lysine. In addition, some amino acid treatments decreased hot temperature-related mortality of broilers indicating the need for amino acid-balanced diets in periods of hot temperature conditions. An isoleucine response occurred in breast meat yield in Experiment 2 indicating the importance of meeting an isoleucine minimum in dietary formulation for growing broilers.