Abstract: The effect of 5-hydroxytryptamine (5-HT) on feed intake has been studied for decades.Tryptophan(Trp), an essential amino acid, is the precursor of 5-HT in the body, which is synthesized in the brain and intestine, and plays an important role in the body.However, 5-HT can not pass through the blood-brain barrier, so the 5-HT in central nervous system and peripheral are two independent systems, and play their roles in dependently.At present, a large number of studies have shown that a variety of central 5-HT receptors regulate animal feeding in different ways, mainly including 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2C, 5-HT3A, 5-HT4, 5-HT5A, 5-HT6 and 5-HT7.For example, lorcaserin, a clinically approved anti-obesity drug, is a 5-HT2C receptor agonist.In addition, central 5-HT can cooperate with peripheral hormones such as glucagon-like peptide-1, ghrelin and cholecystokinin to regulate animal feeding behavior.Peripheral 5-HT can also induce satiety by mediating glucagon-like peptide-1 and cholecystokinin.The increase in the synthesis of 5-HT in animals occurs primarily by the addition of tryptophan to the feed in livestock production.However, the research on the regulatory mechanism of tryptophan on livestock feed intake is not perfect at present.And the study showed that different concentrations of tryptophan had different effects on animal feed intake, and the concentration of optimal tryptophan in different livestock feed.Whereas tryptophan mainly regulates animal feeding through its metabolite 5-HT.Based on a large number of worldwide latest research, this paper is to summarize the research progress of 5-HT in regulating animal feeding behavior through central and peripheral pathways, hoping to provide a theoretical basis for the application of tryptophan metabolite 5-HT to animal feed regulation.

Key words: 5-hydroxytryptamine (5-HT); tryptophan; feeding intake