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Optimizing dietary tryptophan in quail chicks: Implications for NRC (1994) recommendation
Mehran Mehri1, Mahmoud Ghazaghi1, Morteza Asghari-Moghadam1
1Department of Animal Sciences, Faculty of Agriculture, University of Zabol, Sistan 98613-35856, Iran.
Poultry Science
|December 4, 2025
Summary
This study found that modern Japanese quails require higher dietary tryptophan levels than current recommendations for optimal growth, carcass yield, and immune function. Adjusting tryptophan intake supports better performance and health in these birds.
Area of Science:
- Animal Nutrition
- Poultry Science
- Amino Acid Metabolism
Background:
- Dietary tryptophan (Trp) is an essential amino acid crucial for protein synthesis and physiological functions in poultry.
- Current nutritional guidelines may not fully reflect the requirements of modern, rapidly growing quail genotypes.
- Optimizing Trp supplementation is vital for enhancing growth performance, carcass quality, and immune competence.
Purpose of the Study:
- To evaluate the impact of graded dietary tryptophan levels on Japanese quail.
- To determine the optimal Trp requirements for growth, carcass traits, hepatic enzyme activity, and immune response.
- To compare estimated Trp requirements with existing NRC (1994) recommendations.
Main Methods:
- A completely randomized design experiment with 525 seven-day-old Japanese quails.
- Seven dietary Trp levels ranging from 0.21% to 0.27% were administered.
- Growth performance, carcass traits, hepatic enzyme activities (ALP, AST), and antibody titers were assessed.
Main Results:
- Optimal Trp levels for weight gain and feed conversion were estimated at 0.237% and 0.238%, respectively, exceeding NRC (1994) by 7.9-8.3%.
- Hepatic enzyme activities were minimized at specific Trp levels, also higher than NRC recommendations.
- Peak antibody titers and optimal carcass yields (thigh, breast) were achieved at Trp levels 12.2% to 14.1% above NRC (1994) values.
Conclusions:
- Estimated optimal Trp requirements for Japanese quails range from 5.6% to 14.1% higher than NRC (1994) recommendations.
- Modern quail genotypes exhibit increased amino acid demands due to genetic potential and metabolic efficiency.
- Updated nutritional guidelines are necessary to support optimal performance, liver health, and immune function in contemporary quails.
