Effects of Brazilian Pepper Tree (Schinus terebinthifolius Raddi) Ethanolic Leaf Extract on Growth Performance and Expression of Intestinal Immune-Related Genes in Nile Tilapia (Oreochromis niloticus)

This study investigated the ethanolic leaf extract of Brazilian pepper tree (<i>Schinus terebinthifolius</i> Raddi) for its metabolite composition and effects on growth performance and intestinal immune gene expression in Nile tilapia (<i>Oreochromis niloticus</i>). Ultra-performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC-ESI-MS/MS) in positive and negative modes revealed a diverse profile of 33 peaks in each polarity, identifying key compounds such as phenolic acids (e.g., gallic acid and ferulic acid), flavonoids (e.g., myricetin-O-glucoside and quercetin 3-O-glucoside), gallotannins (e.g., glucogallin and pentagalloylglucose), and triterpenoids (e.g., masticadienoic acid). A 60-day feeding trial with four groups (control and three extract doses; 0.5%; T0.5%, 1%; T1% and 2%; T2%) demonstrated dose-dependent enhancements in growth metrics, where final body weight increased by up to 106.9 ± 3.6 g, weight gain% by 197.3 ± 3.5%, and the growth rate got more than doubled in T2% (2.4 ± 0.1), alongside improved feed conversion ratio (1.24 ± 0.01) at 30 days and condition factor (stabilized at 2.1 ± 0.0) at 60 days post-feeding. Viscero- and gastro-somatic indices declined insignificantly in most feed groups, indicating improved muscle growth. Biphasic patterns were observed in intestinal gene expression as follows: over 60 days, the <i>IL-1β</i> gene upregulated at low doses but returned to normal at high doses. The <i>IL-10</i> gene upregulated progressively, promoting an anti-inflammatory balance. In fish fed medium and high doses (T1% and T2%), the <i>IgM</i> gene is upregulated, supporting humoral immunity. These outcomes, linked to the extract's previously described antioxidants, anti-inflammatory, and antimicrobial bioactive compounds, suggest that <i>S. terebinthifolius</i> is a promising natural feed additive for sustainable tilapia aquaculture and warrants further validation for commercial application.