Effects of dietary vitamin E supplementation on growth performance and liver health of Jinhu grouper (Epinephelus fuscoguttatus ♀ × Epinephelus tukula ♂) fed oxidized fish oil diets

This study assessed the efficacy of dietary vitamin E in ameliorating growth and liver function in Jinhu grouper compromised by the inclusion of oxidized fish oil (OFO; peroxide value: 121.68 mmol/kg) in the diet, compared with a fresh fish oil control (FFO; peroxide value: 1.25 mmol/kg). The eight-week feeding trial utilized five experimental diets that were isonitrogenous and isolipidic: FFO, OFO (0 mg/kg VE), or OFO supplemented with 200 (VE1), 400 (VE2), or 600 (VE3) mg/kg vitamin E. Fish receiving oxidized fish oil showed slower growth, indicated by reduced weight gain rate (WGR) and increased feed conversion ratio (FCR). Intake of oxidized lipids altered lipid metabolism, lowering serum total cholesterol (TC), triglycerides (TG), and high-density lipoprotein cholesterol (HDL-C) but elevating low-density lipoprotein cholesterol (LDL-C) and malondialdehyde (MDA) levels. Hepatic antioxidant capacity was compromised, as revealed by the concurrent suppression in both the activities and gene expression levels of key antioxidant enzymes (SOD, CAT, and GPx). Concurrently, oxidized fish oil induced liver inflammation, significantly upregulating pro-inflammatory cytokine genes (notably il-1β , il-6 , il-8 , tnf-α ), and caused histopathological damage including hepatocyte nuclear displacement and lipid droplet accumulation. Vitamin E supplementation ameliorated these effects. The VE2 group (400 mg/kg) maximally restored growth performanc, reduced serum MDA and LDL-C levels, enhanced hepatic antioxidant enzyme activities and gene expression, suppressed inflammatory cytokine expression, and attenuated histopathological lesions. In conclusion, dietary vitamin E supplementation at 400 mg/kg effectively counteracts growth impairment and hepatotoxicity induced by oxidized fish oil in Jinhu grouper. • Oxidized fish oil significantly reduced the growth performance of groupers and caused liver tissue damage. • Dietary supplementation with vitamin E improved feed efficiency and enhanced growth performance. • Vitamin E alleviated hepatic oxidative damage by regulating antioxidant and inflammatory gene expression. • Supplementation with 400 mg/kg vitamin E showed the best protective effect against oxidized fish oil–induced damage.