Digestible lysine responses of male broilers from 14 to 28 days of age subjected to different environmental conditions

Abstract

Dietary amino acid requirements are influenced by environmental conditions. Two experiments examined growth responses of male Ross × Ross TP 16 broilers fed diets varying in digestible Lys concentrations from 14 to 28 d of age under different environmental conditions. Experiment 1 was conducted in July 2007, whereas experiment 2 was initiated during October 2007. In each experiment, dietary treatments consisted of 6 concentrations of digestible Lys and a positive control. Digestible Lys ranged from 0.90 to 1.25% in increments of 0.07% and from 0.92 to 1.32% in increments of 0.08% for experiments 1 and 2, respectively. Linear and quadratic improvements were observed for BW gain and feed conversion in experiments 1 and 2, respectively. In experiment 2, the digestible Lys requirement was estimated at 1.19% based on a quadratic broken-line model and a quadratic regression equation. Digestible Lys intakes that corresponded to the optimal digestible Lys response based on a dietary percentage were estimated at 1,280 and 1,404 mg/d for experiments 1 and 2, respectively. These results suggest that the need for dietary Lys varied considerably with broilers reared in environmental conditions simulating winter vs. summer production when expressed on a digestible Lys intake basis.