Selenium and vitamin E supplementation alleviate high-fat diet-induced stress in oreochromis niloticus: enhancing growth, antioxidant defense, and disease resistance

Abstract This study investigated the interactive effects of dietary fat levels and selenium–vitamin E (Se + VE) supplementation on the growth performance, antioxidant status, immune response, and disease resistance of Oreochromis niloticus . The fish were fed diets containing 5%, 10%, or 15% lipids with or without Se + VE supplementation over a 60-day experimental period. Growth metrics, including final weight, weight gain, average daily gain, and feed efficiency, were significantly improved in the group receiving 10% fat supplemented with Se + VE, whereas high-fat (15%) diets without supplementation resulted in impaired performance ( P < 0.01). Se + VE significantly improved antioxidant enzyme activities (SOD, CAT) and reduced oxidative damage, as indicated by lower malondialdehyde (MDA) levels, particularly under high-fat dietary conditions ( P < 0.0001, with a significant interaction). Proinflammatory cytokines (IL-1β and TNF-α) were elevated by increased fat inclusion, whereas Se + VE mitigated this inflammatory response and elevated anti-inflammatory IL-10 levels. Lipid profile analysis revealed that Se + VE reduced total cholesterol and LDL concentrations while preserving HDL, especially at relatively high fat levels (interaction P < 0.01). The levels of liver enzymes (ALT, AST, and ALP) increased with increasing amounts of dietary fat but were significantly attenuated by antioxidant supplementation. Histopathological assessments of the heart, kidney, and liver confirmed progressive tissue degeneration with increasing fat levels, which was significantly ameliorated by Se + VE. Following challenge with Streptococcus agalactiae , Kaplan–Meier survival analysis revealed significantly improved survival rates in the Se + VE-supplemented groups, with the greatest protection observed in the 5% and 10% fat diet groups. The clinical and pathological scores corroborated these findings, revealing reduced lesion severity in the supplemented groups. Collectively, these results demonstrate that dietary supplementation with Se and VE effectively counters the adverse effects of high-fat diets, improving metabolic balance, tissue integrity, and disease resistance in O. niloticus .