Tryptophan, as a functional essential amino acid, plays important roles in improving growth per-formance, modulating feed intake and lactation, enhancing anti-oxidative and immune functions, and so on in animals.When used as a dietary additive to a low-protein diet, tryptophan will reduce dietary protein level, but not alter production performance of animals, which results in relieving the current protein deficiency and de-creasing the environment pollution caused by the waste of animal production.This paper reviewed the metabolic pathways and physiological functions of tryptophan in livestock...
