<i>Phlogacanthus pulcherrimus</i> Leaf Extract as a Functional Feed Additive: Influences on Growth Indices, Bacterial Challenge Survival, and Expression of Immune-, Growth-, and Antioxidant-Related Genes in <i>Labeo chrysophekadion</i> (Bleeker, 1849).

Abstract

This research examined the impact of dietary supplementation with <i>Phlogacanthus pulcherrimus</i> extract (PPE) on the growth, disease resistance, and expression of immune-, growth-, and antioxidant-related genes in <i>Labeo chrysophekadion</i>. Over 150 days, 90 fish from each group were fed diets with 0 (control), 0.25, 0.50, or 0.75 g/kg of PPE. Phytochemical analysis revealed phenolics (96.00 mg GAE/g), flavonoids (17.55 mg QE/g), anthraquinones, and triterpenoids, along with moderate antioxidant activity (IC₅₀ = 1314.08 μg/mL). One-way ANOVA of growth indices, including weight gain, specific growth rate, feed conversion ratio, and survival rate, revealed no significant differences (<i>p</i> > 0.05); however, PPE supplementation significantly enhanced immune and antioxidant gene expression. <i>IL-1β</i> was significantly (<i>p</i> < 0.05) upregulated at all doses, with the highest expression observed at 0.50 g/kg, showing a fivefold increase compared to the control. In addition, the highest relative expressions of <i>IGF-1</i> and <i>CAT</i> were found at 0.75 g/kg, with 4.5-fold and 3.5-fold increases compared to the control, respectively. PPE at 0.75 g/kg decreased the cumulative mortality rate (CMR) by 20% compared to the control group, which had a CMR of 50% following exposure to <i>Aeromonas hydrophila</i>. PPE acted as an effective immunostimulant and antioxidant, supporting reduced antibiotic reliance in aquaculture.