The effect of L-tryptophan on the food intake, rectal temperature, and blood metabolic parameters of 7-day-old chicks during feeding, fasting, and acute heat stress

Document Type : Full paper (Original article)


PhD Student, Department of Physiology, Faculty of Veterinary Medicine, Shahid Bahonar University of Kerman (SBUK), 76169-133, Kerman, Iran



Background: Exposure to a high ambient temperature (HT) can cause heat stress, which has negative impact on physiological functions. L-tryptophan as precursor of serotonergic and kynurenine pathways, has calmative effect during different stress status. Aim: This study was carried out to determine the influence of intraperitoneal injection of tryptophan on feeding behavior, rectal temperature and some blood parameters in heat stress condition. Methods: L-tryptophan (25, 50 mg/kg body weight) was administered intraperitoneally during either HT (39 °C) or control temperature (CT; 31 °C) for 5 h whilst fed or fasted in 7-day-old chicks. Results: L-tryptophan caused elevation in decreased food intake and significantly decreased rectal temperature during acute heat stress at the dose of 50 mg/kg body weight. Rectal temperature reduced in fasted state at the dose of 50 mg/kg body weight and at the dose of 25 mg/kg body weight tryptophan in fed state in compare with the two other groups. Reduction of serum glucose, triglyceride and corticosterone levels was seen during the fed state. L-tryptophan had significant reducing effect on the serum corticosterone level in fasted state compare with fed state as well had significant decline at the dose of 25 mg/kg body weight on elevated serum corticosterone under heat stress. Conclusion: L-tryptophan led to increase cumulative food intake and decrease rectal temperature during heat stress. Also L-tryptophan cause to decline increased serum corticosterone level under heat stress and fasted state. These finding indicated the potential regulator role of tryptophan to modulate stress response in heat-exposed chicks.


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