<![CDATA[Graphical Abstract Highlight Research 1. Synbiotic diets increased intestinal mucin-2 expression without affecting systemic pro-inflammatory genes (IL-1β and TNF-α). 2. Prebiotic, probiotic, and synbiotic treatment significantly increased non-specific immune responses, such as respiratory burst, phagocytic activity, and plasma protein levels. 3. Prebiotic-fed fish exhibited the greatest weight gain and protein efficiency, indicating better nutrient utilization. 4. A synbiotic cocktail (Bacillus tropicus PCP1, Lactococcus garvieae JAL37, and inulin) reduced mortality after Streptococcus agalactiae challenge, indicating its potential application for early disease prevention. Abstract Aquaculture of red hybrid tilapia (Oreochromis sp.) has been constrained by outbreaks of Streptococcus agalactiae disease. The application of prebiotics, probiotics, and synbiotics has shown potential in modulating host immune responses. This research investigated the effects of probiotic, prebiotic, and synbiotic supplementation on immune-related gene expression, non-specific immune responses, and resistance to Streptococcus agalactiae in red hybrid tilapia. Fish were fed experimental diets supplemented with probiotics (Bacillus sp. PCP1 and Lactococcus sp. JAL37 at 10⁷ cells/g), prebiotic inulin (5 g/kg), and synbiotics for 2 months, in three replicates. The results showed that only the synbiotic treatment increased intestinal mucin-2 gene expression, while all treatments enhanced non-specific immune responses through increased respiratory burst activity, phagocytosis, and total plasma protein. The highest growth performance was observed in fish receiving prebiotic supplementation. In the Streptococcus agalactiae challenge test, probiotic and synbiotic supplementation delayed the onset of mortality until day 4 post-infection. The study concluded that dietary prebiotic, probiotic, and synbiotic supplementation differentially reprogrammed innate immune gene expression in the intestine of red hybrid tilapia, leading to distinct immune responses, increased early resistance to Streptococcus agalactiae infection, and enhanced fish growth. A synbiotic comprising Bacillus sp. PCP1, Lactococcus sp. JAL37, and inulin is advisable to serve as a health management tool prior to immunization.]]>
