Immunostimulatory Potential of Dietary Citronella (Cymbopogon nardus) Powder Combined with Probiotics in Nile Tilapia Infected with Aeromonas hydrophila

Abstract

Motile Aeromonas Septicemia (MAS) caused by Aeromonas hydrophila, is a major bacterial disease in Nile tilapia aquaculture and result in substantial production losses. The excessive use of antibiotics for disease control has raised concerns regarding antimicrobial resistance and environmental contamination, thereby necessitating safer and more sustainable alternatives. This study evaluated the immunostimulatory effect of dietary supplementation with citronella (Cymbopogon nardus) powder combined with probiotics on Nile tilapia challenged with MAS. A completely randomized design was employed using four dietary treatments: a basal diet without supplementation and three experimental diets supplemented with 15 mL of probiotics and citronella powder at doses of 7.5, 10, or 12.5 g per kg of diet (PC-7.5, PC-10, or PC-12.5). Fish were fed the experimental diets for 14 days prior to challenge with A. hydrophila (10⁷ CFU/mL), followed by a post-challenge recovery period. Recovery rate, survival rate, and hematological parameters were assessed. The result indicated that dietary supplementation, particularly PC-7.5, tended to improve recovery and survival rates, although these differences were not statistically significant (P > 0.05). In contrast, hematological parameters were significantly influenced by the dietary treatments (P < 0.05), with PC-7.5 diet producing higher hematocrit, hemoglobin, and leukocyte values, as well as faster hematological recovery following infection. These findings suggest that dietary supplementation with 7.5 g of citronella powder per kg of diet combined with 15 mL probiotics effectively enhances immune response and support disease resistance in Nile tilapia, representing a promising and environmentally friendly strategy for MAS control in aquaculture.