Phytochemical Profiling, Antioxidant and Antibacterial Activities of Persicaria odorata Ethanolic Leaf Extract and Evaluation of Growth Performance, Disease Resistance, and Gene Expression in Labeo chrysophekadion (Bleeker, 1849)

<i>Persicaria odorata</i> is a medicinal plant recognized for its diverse biological activities. This study investigated the phytochemical profile, antioxidant and antibacterial activities of <i>P. odorata</i> ethanolic leaf extract (POE), as well as its effects on growth performance, disease resistance, and gene expression in <i>Labeo chrysophekadion</i> (Bleeker, 1849) over 150 days. Qualitative screening of POE confirmed the presence of phenolics and flavonoids associated with antioxidant and antibacterial properties. Quantitative analysis determined total phenolic and flavonoid contents in POE, and HPLC confirmed the presence of quercetin and catechin. The extract exhibited notable antioxidant capacity and antibacterial activity against selected pathogens. Dietary supplementation with POE at different inclusion levels resulted in numerically higher growth indices than the control, although differences were not statistically significant (<i>p</i> > 0.05). Fish fed 0.50 and 0.75 g/kg POE showed reduced cumulative mortality compared with the control and 0.25 g/kg group (<i>p</i> < 0.05). POE supplementation also upregulated <i>IL-1β</i> and <i>IGF-1</i> expression, suggesting enhanced immune responses and growth regulation. Overall, POE shows potential as a natural feed additive to support fish health and disease resistance in aquaculture.