L-Threonine is an essential amino acid which is often added to the feed of immature piglets and poultry, and it is the second limiting amino acid of pig feed and the third limiting amino acid of poultry feed. Adding L-Threonine to compound feed can adjust the amino acid balance of feed, promote the growth of livestock; improve the quality of meat; improve the nutritional value of feeds with low amino acid digestibility; and reduce the cost of feed ingredients. L-Threonine has rich nutritional value. L-Threonine can be used to balance amino acids, promote protein synthesis and deposition, eliminate weight loss caused by excessive lysine, and reduce growth inhibition caused by excessive tryptophan or methionine; it can be converted into other amino acids after absorption into the body. Lack of L-threonine may inhibit the production of immunoglobulins and T.B. lymphocytes, thus affecting the immune function.