Immunomodulatory, behavioral, and nutritional response of tryptophan application on poultry

Abstract

Tryptophan is an essential amino acid for all animals that was discovered through casein hydrolysis. The use of tryptophan as feed additives has been attracting the attention of many nutritionists because it cannot be synthesized enough in an animal's body. Tryptophan or precursor to the vitamin niacin in the diet is important, and its supplementation for poultry is determined to improve the amino acid balance and promote the poultry's growth performance through enhancing appetite, feed efficiency, and protein synthesis. Moreover, poultry in different growth phases, breeding, and conditions require various amounts of tryptophan. In addition, supplemented tryptophan also improves the immune response or the immunomodulatory activity of poultry to various diseases through the kynurenine pathway, especially diseases in the bursa. Furthermore, tryptophan also has a strong relationship with lysine (the ideal tryptophan/lysine ratio) in improving growth performance. However, tryptophan deficiency could affect the behavioral responses (e.g. pecking behavior and poultry stress) because tryptophan serves as a precursor for the neurotransmitter serotonin and the pineal hormone melatonin in the diet. This paper tried to summarize all information about applying tryptophan in the diets and illustrate the roles of tryptophan in the poultry industry.

Malfunctioned inflammatory response and serotonin metabolism at the microbiota-gut-brain axis drive feather pecking behavior in laying hens

“…As Phe is metabolized to Tyr to produce the precursor of the catecholamine neurotransmitters, such as dopamine, which activity in the brain is closely related to SFP behavior ( Kops et al, 2017 ). Additionally, tryptophan metabolism affects the homeostasis of the animal's gut-brain axis, enhancing the body's immune response or the immunomodulatory activity through the kynurenine pathway ( Fouad et al, 2021 ), and affecting the behavioral responses (e.g., pecking behavior, stress-related, fearfulness) via the 5-HT metabolic pathway ( Linh et al, 2021 ). Here, we found that differential metabolites between the 2 FP phenotypes were mainly enriched in the tryptophan metabolism.…”

Allantoic fluid metabolome reveals specific metabolic signatures in chicken lines different for their muscle glycogen content

“…Due to its anti-inflammatory, anti-oxidant and anti-apoptotic activities in a variety of cells and tissues, nicotinate is actively involved in the prevention of many pathological processes 31 , 32 . Nicotinate is mainly synthesized in the liver through the kynurenine pathway, which is the major catabolic route of tryptophan 33 , 34 . From E14 onwards, nicotinate was not detected in the allantoic fluid, while kynurenine accumulated, and to a greater extent, in the pHu− line compared to the pHu+ line.…”

Applications of Enteroendocrine Cells (EECs) Hormone: Applicability on Feed Intake and Nutrient Absorption in Chickens

“…Moreover, peripheral serotonin increased intestinal motility and reduced plasma leptin and adiponectin concentrations, which can decrease appetite [ 159 ]. In poultry, insufficient tryptophan has been known to decrease serotonin synthesis [ 162 ]. However, most studies have focused on stress mitigation and meat quality, but not feed intake.…”