Isoleucine is one of the three branched-chain essential amino acids (BCAAs) that animals cannot synthesize on their own. Together with leucine and valine, it participates in protein synthesis, gluconeogenesis, and fat metabolism, playing an irreplaceable role in promoting muscle tissue repair, maintaining blood glucose stability, regulating immunity, and alleviating weaning stress. In low-protein diets for pigs and poultry, the balanced ratio of isoleucine to lysine and valine (Ile:Lys) is one of the key bottlenecks limiting animal growth performance, with significant effects on intestinal development in piglets and milk production in sows. Feed-grade products are mainly added in the form ofL-isoleucine (content ≥98%)and are widely used in piglet, sow, and broiler diets, making them an indispensable component in precision amino acid balancing formulations.