Growth performance, carcass characteristics, ileal microbiota, and amino acid digestibility of broilers fed diets varying in supplemental copper concentrations and amino acid density from 1 to 32 d of age

Abstract

Summary Two experiments were designed to determine interactive effects of supplemental dietary Cu and amino acid (AA) density on growth performance, processing characteristics, ileal microflora, and AA digestibility of broilers. In experiment 1, 8 dietary treatments were used, consisting of a factorial arrangement of 3 Cu programs providing Cu concentrations of 135-135-135, 270-135-135, or 270-270-135 mg/kg in starter, grower, and finisher periods, formulated at moderate or low AA density, positive and negative controls. The Cu source was tribasic Cu chloride. In both experiments, control birds were provided with diets formulated to moderate AA density and approximately 13 mg/kg Cu. Broilers fed positive control diets were unvaccinated and received diets containing a coccidiostat, while all other birds were vaccinated against coccidiosis. The results indicated that feeding high concentrations of dietary Cu may decrease feed conversion ratio through reduced feed intake. This led to reduced carcass weight and yield, but did not affect breast meat weight and yield. No differences were observed for microflora composition. Experiment 2 evaluated apparent ileal AA digestibility and used 6 dietary treatments, consisting of positive and negative controls and a factorial of either 135 or 270 mg/kg Cu and low or moderate AA density. Copper treatments reduced Cys digestibility compared with negative control–fed birds, and only Trp digestibility was increased with Cu supplementation. These studies indicate that feeding high concentrations of Cu may enhance growth performance but did not improve digestibility of most AA or alter microflora profile.