Determination of the Arginine, Tryptophan and Glycine Ideal-Protein Ratios in High-Yield Broiler Chicks

Introduction: Requirements for dietary amino acids (AA) in broilers may be affected by a variety of nutritional, environmental, genetic, or management factors. In order to address these variations in diet formulation, ideal ratios of indispensible AA to digestible (d) Lys, which remain relatively unaffected by these factors, may be used instead [1]. Nutritionists have successfully applied the ideal protein concept to produce diets that provide adequate AA content for many years. The ideal ratios for many of the limiting AA of traditional corn-soy diets have been wellestablished in broilers. Other AA, such as dArg, Gly, and dTrp are typically assumed to be provided in excess in a corn-soy diet and therefore have not been investigated as thoroughly. Recently, alternative feedstuffs have been increasingly utilized as cost-effective substitutes for portions of traditional ingredients such as corn and soybean meal. Increased inclusion of alternative feedstuffs may allow dArg, dTrp and Gly levels to become marginal. Additionally, genetic selection for increased breast meat yield may have altered the AA needs of the modern broiler with respect to these AA. Formulation based on the ideal protein concept is advantageous for broiler nutritionists. However, ideal ratios for amino acids such as dArg, Gly, and dTrp have not been evaluated in modern, broiler strains.