The inclusion of feed-grade amino acids in diet formulation has allowed nutritionists to formulate diets more economically to enhance the efficiency of growth and reproduction in commercial poultry production. Diets had been traditionally formulated on a crude protein basis. Synthetic Met was used in diet formulation in the 1970’s and this technology significantly reduced dietary cost. In the 1980’s, crystalline Lys was manufactured to further reduce diet cost and later contributed to enhancing meat yield with the development of the deboning market with less emphasis being placed on whole birds. The industry was unable to fully utilize the concept of reduced crude protein diets without a minimum being placed on the next limiting amino acid as crude protein could be reduced over 3% points and negatively impacting performance. Crystalline Thr was introduced in the late 1990’s and after 15 years of research the broiler industry adopted this technology to further reduce diet cost by $5.0 per ton with a 1 kg inclusion of L-Thr. In 2009, L-Val was commercially available to be included in poultry diets to further decrease dietary cost with the use of reduced crude protein diets without compromising growth performance and meat yield. Dietary Ile, Arg, and Trp are regarded as the fifth, sixth, seventh limiting amino acids in corn-soybean meal-based diets. Knowledge gaps in the literature exist in broilers of different growth phases with these less limiting amino acids, but these amino acids are important in diet formulation. In addition to determining optimum digestible ratios of these less limiting amino acids for various growth phases, it is also important to evaluate amino acid interactions, specifically with amino acids involved in antagonisms. Moreover, less limiting amino acids need to be assessed for reproduction and the use of L-Trp with behavioral issues during rearing and laying periods.