Dietary Application of Chlorophytum borivilianum and Withania somnifera Root Extracts Stimulates Growth, Immunity and Resistance Against Aeromonas hydrophila Infection in Nile Tilapia, Oreochromis niloticus

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Using synthetic antibiotics in Nile tilapia culture poses health and environmental risks. Efforts are made to use phytochemicals as safer alternatives with optimum effect on fish yield. The present study aimed to determine the anabolic, immunomodulatory, anti-pathogenic effects of Chlorophytum borivilianum root ethanol (EC) and Withania somnifera root methanol (MW) extract in Nile tilapia during 120 d grow-out culture in cement cisterns. Juvenile Nile tilapia (0.020 ± 0.001 g; 1.02 ± 0.011 cm) were divided into three groups with three replicate cisterns each. One group was fed EC fortified diet, the second group was fed MW fortified diet (both at 0.75 g extract per kg feed) for 30 d followed by a basal diet for the next 90d, while another group was fed a basal diet for 120 d. Fish fed plant extract-fortified diets showed significantly better (P < 0.05) weight gain (g), specific growth rate (%), immunostimulatory (phagocytic, lysozyme activities, respiratory burst), haematological and biochemical parameters than those fed the control diet. After 120 d, fish from each treatment group were challenged with the heterotrophic bacterium Aeromonas hydrophila [intraperitoneal injection with 0.1 mL (in saline solution) single sub-lethal dose (5 ×105 CFU.mL-1)]. Seven days post-infection, fish fed plant extract-fortified diets showed significantly better (P < 0.05) survival, immunological, haematological and biochemical parameters than control fish. The bioactive phytoconstituents in the plant extracts might be responsible for their growth-enhancing and anti-pathogenic effects. Dietary administration of MW yielded significantly better (P < 0.05) growth-promoting effects and resistance against A. hydrophila infection in Nile tilapia than EC extract.