Swine nutrition has focused the last fifteen years of research on reducing dietary crude protein to reduce dietary costs, improve efficiencies and manage environmental impact of swine production. Through the implementation of feed grade amino acids, research concerning the amino acid requirements of pigs in relation to the first limiting amino acid has expanded through the first six amino acids. Furthermore, complex models such as central composite designs can be used to evaluate the interaction of competitive uptake amino acids such as the branched chain amino acids relative to each other. Research has demonstrated the impact of reducing crude protein on grow-finish pig growth and environmental impact. For example, a recent study by Hagen et al. (2024) demonstrated that reducing crude protein in diets resulted in improved feed efficiency (G:F 0.73 vs 0.71, respectively). Through the utilization of various research models, the determination of exact amino acid requirements have been successful. Multiple amino acids demonstrate that the requirement of feed intake or growth are different than that associated with feed efficiency. For example, feeding a lower level of Trp:Lys resulted in the optimal response in average daily gain, but a higher ratio is needed to maximize gain:feed in various phases of production (Liu et al. 2019). Humphrey et al. (2024) demonstrated that average daily gain was optimized when SID Arg:Lys was 95.65% and feed intake was optimized at 97%. Hagen et al. (2024) demonstrated that providing feed grade amino acids in the water can enhance feed efficiency and the utilization of Arg in the water can assist in helping reduce the impact of enteric challenges. Lastly, understanding how the amino acids interact with one another beyond the relationship to Lys has been of significant impact. Humphrey et al. (2023) demonstrated that the response of Val is independent of Leu and Ile, but when Val is deficient then ADFI can be impacted by high levels of Leu. Furthermore, ADG and G:F can be reduced when feeding higher levels of Leu and Ile and responds to lowering either amino acid independently. However, there were no changes in feed intake when evaluating similar branched chain amino acid ratios in sow lactation diets.