Enhancing Growth and Immune Responses in Giant Freshwater Prawn (Macrobrachium rosenbergii) via Oral Administration of Fennel (Foeniculum vulgare) Extract against Vibrio parahaemolyticus

Abstract

This study investigated the effects of dietary supplementation with Foeniculum vulgare ethanolic (FVE) extract on growth performance, immune response, nutritional composition and disease resistance in Macrobrachium rosenbergii against Vibrio parahaemolyticus. Juvenile prawns (2.1 ± 0.25 g) were assigned to three dietary groups in triplicate (15 prawns/tank) including a basal diet (control), 0.25% or 2.5 g/kg FVE extract (T₁), and 0.5% or 5.0 g/kg FVE extract (T₂). After an 8-week feeding trial, prawns were challenged with V. parahaemolyticus (10⁶ CFU/mL), and survival was monitored for 14 days. The T₁ group demonstrated significantly superior growth metrics, including final weight (FW), average weight gain (AWG), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), proximate composition (protein, lipid and ash percentage), and enzymatic activity (Amylase, Protease) compared to both control and T₂ groups. Immune-related parameters such as total haemocyte count (THC), hemolymph clotting time (HCT), superoxide anion production, respiratory burst (RBs) activity, pro-phenoloxidase (proPO) activity, and superoxide dismutase (SOD) activity were significantly elevated in FVE supplemented groups both pre- and post-challenge. While control prawns suffered complete mortality (100%) within 14 days, T₁ and T₂ groups demonstrated significantly higher survival rates. Notably, the 0.25% FVE dose optimally enhanced growth, feed efficiency, and immune function compared to the higher dose. These findings indicate the utility of FVE extract as a sustainable, natural alternative to synthetic aquaculture additives. This study advances the role of phytogenic supplements in enhancing aquatic health management and productivity, aligning with eco-friendly aquaculture practices.