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Abstract This study investigated the antibacterial activity of Phyllanthus amarus extracts and its influence on the growth, physiological and immune status of Clarias gariepinus fingerlings. The fish were fed diets containing 0.0 (control), 0.5, 1.0, 1.5 or 2.0g P. amarus extract (PAE)/kg basal diet to apparent satiation for 84 days. Thereafter, blood samples were collected from the fish and used for haematological and biochemical analyses. After the 84-day feeding, the fish were challenged with Aeromonas hydrophila by intraperitoneal injection, observed for survival, and immune response parameters were measured. Data were analyzed using one-way analysis of variance at P < 0.05. Results showed significant antibacterial activity of P. amarus methanol extract against A. hydrophila and its application at 0.5 -1.5g PAE significantly promoted weight gain and specific growth rate, with the highest at 1.0g, while the feed conversion ratio reduced significantly at these levels, compared to the fish fed the control diets. Haematocrit, haemoglobin and lymphocytes were enhanced at 0.5-1.5g PAE. All fish fed PAE-based diets had lower concentration of serum liver enzymes, with the least in fish fed 1.0-1.5g PAE diets, while the values of creatinine, glucose and total bilirubin did not differ among the treatments. Glutathione peroxidase and glutathione‐S‐transferase activities increased in all PAE-fortified treatments. Lysozyme, phagocytic and respiratory burst activities also increased in the challenged fish fed PAE diets. Post-challenge survival was highest at 1.0g PAE. Therefore, inclusion of 1.0g Phyllanthus amarus extract is recommended as dietary supplement for Clarias gariepinus.
Adeniyi et al. (Wed,) studied this question.