Modulation of growth, blood physiology, disease resistance, molecular immune-antioxidant gene expression, and tissue integrity in european seabass (Dicentrarchus labrax) fed Moringa oleifera flower-enriched diets

Herbal-based additives are now recognized as effective tools of growth and immunity in aquaculture. Seeking these botanical alternatives is a practical necessity for sustainable farming and chemical reduction. Moringa oleifera flowers (MOF), in particular, offer significant potential due to their established history in treating inflammation and respiratory conditions. However, the potential of these additives to enhance growth, physiological status, and tissue health in European seabass (Dicentrarchus labrax) has not yet been evaluated. A 70-day feeding trial was conducted to evaluate the effects of graded dietary levels of M. oleifera flower (MOF) on the growth performance, immune- and antioxidant-related genes, physio-metabolic profile, and redox homeostasis of European seabass and resistance to Vibrio alginolyticus challenge. Fish were allocated to four experimental groups and fed either a basal diet (control, MOF0) or the basal diet supplemented with MOF at concentrations of 1 (MOF1), 2 (MOF2), and 3 (MOF3) g/kg. Dietary MOF supplementation significantly enhanced growth indices and the whole-body proximate composition of D. labrax compared to the control group (P< 0.05). Furthermore, fish fed MOF-enriched diets exhibited significant elevations in hematological parameters, including (hemoglobin, RBCs, MCH, MCHC, and WBC) counts (P< 0.05). Metabolic and antioxidant profiles were similarly improved, characterized by a significant increase in total serum protein and a concomitant reduction in glucose, cholesterol, and hepatic enzyme activities (AST, ALT, and ALP) (P< 0.05). Dietary MOF inclusion mitigated oxidative damage by decreasing MDA levels while simultaneously enhancing the enzymatic antioxidant defense system (SOD, CAT, and GPx) (P< 0.05). These biochemical improvements were supported by molecular data showing a significant upregulation of growth genes (IGF-I and GH), pro-inflammatory and complement system genes (IL-1β and C3), and antioxidant enzymes (SOD and GPx) (P< 0.05). MOF inclusion in the diets of D. labrax supported systemic tissue health by improving the structural integrity of the intestinal mucosa and preventing degenerative changes in the hepatic parenchyma and muscle fibers. These findings underscore the multi-tissue cytoprotective efficacy of MOF in D. labrax. Following the V. alginolyticus challenge, fish in the MOF2 and MOF3 groups exhibited significantly higher survival rates and enhanced pathogen resistance compared to the MOF0 and MOF1 cohorts (P< 0.05). Consequently, our data suggest that a dietary inclusion of 2 g/kg of M. oleifera flowers represents an effective strategy for optimizing growth performance, immunocompetence, and antioxidant capacity in European seabass.