Abstract
Background:
Poultry is the fastest-growing animal in agriculture sector and feed cost contributes 70-80% of production cost, therefore many efforts has been evaluated to reduce feed cost. One of these ways to improve feed efficiency is the use of natural feed additives in the diet, especially after reducing the use of antibiotics in poultry diets. Flaxseed contains bioactive compound, particularly omega-3 fatty acids (α-linolenic acid) and lignans which used to improve energy metabolism and plays as an antioxidant and anti-inflammatory effect in poultry diets. Vitamin E plays a vital function in protecting polyunsaturated fatty acids from oxidative damage, preserving cell membrane integrity, and supporting immune functions.

Aim:
This study aimed to evaluate the physiological and productive effects of flaxseed (Linum usitatissimum) and vitamin E supplementation, individually or in combination, in Japanese quail (Coturnix japonica)

Methods:
A total of 120 quails were randomly assigned to four dietary treatments: commercial diet (control), commercial diet with flaxseed, commercial diet with vitamin E, and commercial diet with both flaxseed and vitamin E, each group comprising three replicates with 10 chicks per replicate and the study lasted five weeks following one week of adaptation

Results:
The combined supplementation markedly enhanced growth performance, improving body weight gain, feed efficiency, and survivability compared with the control group. Serum biochemical analysis revealed improved protein metabolism and a healthier lipid profile, with reductions in cholesterol, triglycerides, and low-density lipoprotein (LDL), alongside an increase in high-density lipoprotein (HDL). Antioxidant indices confirmed strengthened defense mechanisms, as glutathione levels increased and malondialdehyde (MDA) concentrations decreased, while liver enzyme activities, Aspartate Transaminase (AST) and Alanine Transaminase (ALT) were reduced, indicating improved hepatic function. The synergistic interaction between omega-3 fatty acids from flaxseed and the antioxidant role of vitamin E contributed to better metabolic efficiency and oxidative stability.

Conclusion:
These findings highlight flaxseed and vitamin E can be fed to Japanese quail as promising natural feed additives that can enhance productivity, health status, and sustainability in quail production.

Key words: Flaxseed; Growth performance; Japanese quail; Vitamin E.