Dietary Moringa oleifera Attenuates Cadmium and Copper-Induced Haematological Toxicity and Restores Immune Homeostasis in the Catfish Clarias batrachus

Abstract

Heavy metal contamination of freshwater ecosystems by cadmium (Cd) and copper (Cu) is a major threat to fish health and aquaculture productivity, particularly across the industrially impacted river systems of the Indo-Gangetic plain. The present study evaluated the restorative and protective efficacy of dietary Moringa oleifera leaf meal against sublethal cadmium sulphate and copper sulphate toxicity in the air-breathing catfish, Clarias batrachus, with an emphasis on haematological derangement and immune homeostasis. Ninety-six-hour LC50 values were established at 12.42 mg/L (cadmium) and 0.58 mg/L (copper), and fish were chronically exposed to one-tenth LC50 concentrations for 60 days while receiving either a basal diet or a diet supplemented with 40% M. oleifera leaf inclusion (MLI). Both metals produced progressive anaemia, characterised by reduced total erythrocyte count (TEC), haemoglobin (Hb) and packed cell volume (PCV), together with leucocytosis, neutrophilia and lymphopenia indicative of a chronic inflammatory, immunosuppressive response. Dietary Moringa supplementation restored TEC by 76.3-78.6%, Hb by 71.4-73.7% and PCV by 68.2-68.3% of control values, while normalising the lymphocyte-neutrophil ratio and reducing erythrocyte morphological abnormalities by over 61%. In vitro batch-sorption assays confirmed that M. oleifera leaf powder chelates cadmium and copper (81.2% and 77.5% removal efficiency, respectively) through carboxylic acid and hydroxyl functional groups, a finding that explained 86.4% of the variance in in vivo protective efficacy. These results establish M. oleifera as a locally available, cost-effective dietary intervention capable of restoring haematological and immune homeostasis in metal-stressed catfish, with direct relevance to sustainable aquaculture in metal-contaminated tropical freshwater systems.