Amino acids are organic compounds that serve as building blocks of protein. There are over 700 amino acids found in nature but only 20 are used in protein synthesis. Amino acids are classified as essential, non-essential, and semi-essential depending on an animal's ability to synthesize them. Most amino acids exist in two isomeric forms (L and D) but only the L-form is used in protein synthesis. Imbalances or deficiencies in amino acids can negatively impact animal health and performance. Amino acids interact with each other and have many important functions including protein synthesis, gene expression, hormone production, nutrient metabolism, immune function, and more.