Threonine requirement of the broiler chick as affected by protein level and source

The threonine requirement of the young broiler chick was estimated in two experiments. In Experiment 1, a threonine-deficient corn-peanut meal-amino acid mixture was included in a basal diet at levels equivalent to 15 and 20% crude protein. In Experiment 2, a purified crystalline amino acid mixture, also limiting in threonine, was included in a basal diet at levels equivalent to 10.98 and 18.3% crude protein. When expressed as a percent of diet, the estimated threonine requirements increased as dietary protein content increased. However, when expressed as a percent of dietary protein, the estimated threonine requirements were not significantly affected by dietary protein content, and were similar for the two experiments. It was concluded that the threonine requirement is 3.7% of dietary crude protein, and is little affected by dietary protein content.