Vitamin B9 (folate) is an important water-soluble vitamin in animal feed. As a key coenzyme in one-carbon unit transfer, it plays a central role in the synthesis of nucleic acids (DNA/RNA), protein metabolism, and cell division and proliferation. In livestock production, it is essential for maintaining rapid growth (especially in young animals), normal hematopoietic function (preventing anemia), and good reproductive performance. Specifically, folate effectively supports early embryonic development and reduces malformation rates; improves egg production and hatchability in breeding poultry; and maintains skin and coat health. Deficiency can lead to growth retardation, anemia, reproductive disorders (such as embryonic death and reduced sperm quality), and poor feather or hair development. Although rumen microorganisms in ruminants can synthesize some folate, monogastric animals (e.g., pigs and poultry) cannot synthesize it on their own, and their requirements increase under high-intensity production, compromised intestinal health, or use of antibacterial agents. Therefore, supplementation in complete feed is necessary, particularly in diets for breeding, gestating, and rapidly growing animals.