**Abstract**

The interconnected nature of the amino acids in broiler nutrition pose an interesting quandary for poultry nutritionists. Two primary antagonisms exist in poultry, that among lysine and arginine and the branched-chain amino acids. Throughout the discovery and investigation into these amino acids, researchers have questioned the existence of these antagonisms as well as their impact on practical formulation. The lysine-arginine antagonism was the first discovered in poultry and was largely solved when protein formulation shifted from crude protein requirements to formulation based on amino acid levels. In contrast, while branched-chain amino acid antagonism was discovered over 50 years ago, increased refinement of dietary amino acid profiles has allowed for this antagonism to become a reemerging concern. These antagonisms and the interplay of amino acids on dietary requirements will continue to challenge researchers for years to come and innovative formulation strategies will need to be developed in order to optimize broiler diets and production.

**Keywords:** arginine, lysine, amino acid antagonism, branched-chain amino acids, leucine
