Dietary Supplementation with Gotu Kola (Centella asiatica) Extract Enhanced Innate Immune Responses, Modulated Immune-Related Gene Expression, and Improved Gut Microbiota in Giant Freshwater Prawn (Macrobrachium rosenbergii)

The giant freshwater prawn (<i>Macrobrachium rosenbergii</i>) has economic significance in the aquatic industry, but production is impacted by infectious diseases induced by various pathogens. Herein, we investigated the impact of adding feed additives to the diet of <i>M</i>. <i>rosenbergii</i> to promote health. Diets were formulated to contain different levels of <i>Centella asiatica</i> (L.) Urb. crude extracts (1, 5, and 10 g kg^-1), with growth performance and innate immune parameters assessed after 28 days of feeding. Real-time quantitative PCR (RT-qPCR) was employed to determine the mRNA levels of <i>serine proteinase inhibitor</i> (<i>SPI</i>) and <i>alpha-2 macroglobulin</i> (<i>Mr-2α2M</i>) from 12 h to 28 days of feeding. Prawns feeding at 5 and 10 g kg^-1 showed statistically significant differences in specific growth rate, lysozyme assay, and phenoloxidase activity. The expression levels of all the immune-related genes studied were significantly upregulated in prawns fed with supplemented diets compared to the control group. Findings revealed that the observed upregulations varied in response to alterations in feeding time and concentration. Furthermore, 16S rRNA analysis showed that the supplemented diets at 10 g kg^-1 supplementation increased beneficial bacteria (<i>Lactococcus</i> sp.) and reduced pathogenic taxa (e.g., <i>Candidatus Hepatoplasma</i>, <i>Flavobacteriaceae</i>, <i>Weeksellaceae</i>, <i>Thiothrix</i> sp.).