Effects of dietary Vitamin A on growth performance, antioxidant and immune capacity of mandarin fish (Siniperca chuatsi)

This study investigated the effects of dietary vitamin A (VA) on growth performance, antioxidant capacity, immune function, and intestinal health in juvenile mandarin fish (Siniperca chuatsi). Six iso-nitrogenous and iso-lipidic diets containing graded VA levels (2430 [A1], 4765 [A2], 7550 [A3], 10,674 [A4], 13,847 [A5], and 16,896 [A6] IU/kg) were fed to triplicate groups (15 fish/tank, 81.67 ± 0.51 g) for 8 weeks. The results revealed that growth performance peaked at A3 group for FBW, WGR, and SGR, while FCR and FE optimized at A4 group. T-AOC, SOD, and CAT activities peaked in A3-A4 groups, with MDA levels minimized at A3-A4 groups.VA supplementation upregulated cat, gpx, and sod mRNA expression while suppressing keap1a, particularly in A3-A4 groups. Immune parameters (IgM, C3, C4) and antimicrobial genes (hepcidin, defensin-β, viperin) showed the highest levels at A3-A4 group, accompanied by anti-inflammatory cytokine upregulation (il-10, tgf-β1) and NF-κB pathway inhibition. Histological analysis revealed enhanced the integrity of spleen, head kidney and intestine at A4 group. Gut barrier markers (D-LA, DAO, ET) and tight junction genes (claudin, occludin) optimized at A3-A4 group. 16S rRNA sequencing revealed that appropriate vitamin A supplementation improved the intestinal microbial structure andα-diversity of S. chuatsi. A quadratic regression analysis established the most effective vitamin A dosage to be between 9255.6 and 9280.0 IU/kg, as determined by WGR and FCR.