Ratio of digestible total sulfur amino acids to lysine of broiler chicks from 1 to 15 days of age

Abstract

SUMMARY Two experiments were conducted to determine digestible (dig) TSAA to Lys ratios of diets fed to male Ross × Ross 708 and Hubbard × Cobb 500 broilers from 1 to 15 d. In each experiment, 1,600 male broilers were randomly distributed into 64 floor pens and fed 8 experimental diets consisting of 8 ratios of ileal dig TSAA to Lys, ranging from 0.56 to 0.84 in increments of 0.04. A standardized Lys digestibility assay was conducted with broiler chicks to determine the amino acid digestibility of the basal diets. Standardized TSAA digestibility of the basal diets was determined to be 0.65 in both experiments. In experiment 1, progressive additions of dig TSAA to Lys resulted in a significant linear effect for d 1 to 14 feed conversion. An optimum TSAA to Lys ratio was determined to be 0.74 based on d 1 to 14 feed conversion using a linear broken-line model. In experiment 2, optimal dig TSAA to Lys ratios were estimated to be 0.78 and 0.77 for feed conversion from d 1 to 7 and d 1 to 14, respectively, based on a quadratic broken-line model. Therefore, based on these data, the dig TSAA requirements for optimal growth performance of modern broilers are higher than previously reported.