# Dietary oregano essential oil and sodium butyrate enhance growth, immunity, and gene expression in nile tilapia post-Aeromonas hydrophila infection

## TL;DR

Adding oregano oil and sodium butyrate to Nile tilapia diets improves growth, immunity, and gene expression after infection.

## Contribution

Demonstrates that dietary oregano essential oil and sodium butyrate at 1% improve health and immunity in Nile tilapia post-infection.

## Key findings

- Fish fed 1% oregano oil and sodium butyrate had highest body weight and lowest feed conversion ratio.
- Supplemented diets improved hematological, biochemical, and immunological parameters.
- Gene expression of immune and antioxidative markers was upregulated in supplemented groups.

## Abstract

The impacts of oregano essential oil and sodium butyrate on the growth performance, hematological, biochemical, immunological, antioxidative, and gene expression profiles of Nile tilapia (Oreochromis niloticus) fingerlings were examined in this study. One hundred eighty healthy fingerlings (16.00 ± 2.00 g) were acclimated and accidentally divided into three groups, each further split into three replicates. The groups were fed a basal diet (control) or diets supplemented with 0.5% and 1% oregano essential oil and sodium butyrate for eight weeks (The feed additives were administered continuously throughout an 8-week trial period, simulating a practical feeding strategy that would be feasible during high-risk periods (e.g., post-handling stress, seasonal disease outbreaks). Fish fed the supplemented diets demonstrated significantly greater growth performance, with the oregano 1% + sodium butyrate 1% group achieving the highest final body weight (36.91 ± 0.66 g) and lowest feed conversion ratio (1.32 ± 0.04). Hematological indices, including RBC count, Hb, and PCV, were substantially improved. Biochemical analysis revealed reduced ALT, AST, urea, and creatinine levels alongside elevated total protein and globulin concentrations in treated groups. Immunological and antioxidative parameters, such as WBC count, phagocytic activity, SOD, and GPX, showed significant enhancements, particularly in the oregano 1% + sodium butyrate 1% group. Gene expression analysis exposed upregulation of immune-related (TNF-α, IL-1β) and antioxidative (SOD, GPX) genes in supplemented groups, highlighting their role in enhancing health and stress responses. Post Aeromonas hydrophila infection, the supplemented groups exhibited improved immunity, antioxidative status, and survival. These findings suggest that dietary supplementation with oregano essential oil and sodium butyrate, particularly at 1% inclusion, effectively enhances growth, health status, immunity, and gene expression in Nile tilapia.

The online version contains supplementary material available at 10.1038/s41598-025-22439-8.