Effect of the balance between flaxseed and animal fat on FADS2 gene expression in the liver of Japanese quail (Coturnix japonica)

This study investigated the effects of dietary lipid composition on hepatic FADS2 gene expression in Japanese quail (Coturnix japonica), focusing on graded combinations of animal fat and flaxseed inclusion. A total of 80 quail were randomly allocated into four dietary groups (n = 20 per group), in which animal fat levels were progressively increased (0–5%) while flaxseed levels were decreased (5–0%). All diets were formulated to contain approximately 24% crude protein and 3000 kcal/kg metabolizable energy. At the end of the experimental period, hepatic tissue samples were collected, and FADS2 gene expression was quantified using real-time PCR. Relative gene expression was calculated using the 2⁻ΔΔCt method with ACTB as the reference gene. Statistical analysis was performed using one-way ANOVA followed by Tukey’s post hoc test. Results demonstrated a significant effect of dietary treatment on hepatic FADS2 expression (P < 0.001). Relative expression analysis revealed a progressive increase in FADS2 expression across dietary groups, with fold changes of 1.18, 2.94, and 4.75 in Groups 2, 3, and 4, respectively, compared with the calibrator group. Post hoc analysis indicated significant differences particularly between low and high animal fat inclusion groups. The response pattern suggested a non-linear modulation of hepatic FADS2 expression in response to dietary lipid composition. In conclusion, increasing dietary animal fat levels combined with decreasing flaxseed supplementation significantly upregulated hepatic FADS2 gene expression in Japanese quail. These findings suggest that dietary fatty acid composition is an important regulator of hepatic lipid metabolism at the transcriptional level and may be relevant for nutritional strategies aimed at modulating lipid quality in poultry products.