Study of effects of dietary quercetin (Que) on growth performance and disease resistance mechanism of Litopenaeus vannamei

The purpose of this study was to evaluate effects of dietary quercetin (Que) on growth performance and disease resistance mechanism of Litopenaeus vannamei. Shrimp were randomly divided into 4 groups, with 3 replicants in each group and 70 shrimp in each replicants. The contents of Que. in the four groups were 0, 0.25, 0.5 and 1 g kg⁻¹, respectively. Samples were taken after 56 days, followed by a 3-day white spot syndrome virus (WSSV) challenge experiment. The results showed that Que. significantly improved the growth performance and reduced the content of crude fat in shrimp (P < 0.05). Dietary Que. increased phagocytic activity, bacteriolytic activity and antibacterial activity (P < 0.05), but had no effects on the total hemocytes count. Dietary Que. also improved the expression levels of genes related to immunity of shrimp. In addition, dietary Que. improved the activities of catalase and glutathione peroxidase, total antioxidant capability and the content of glutathione (P < 0.05), but decreased the superoxide dismutase activity (P < 0.05). In the case of intestinal microbiota, Que. reduced microbial diversity and richness. Meanwhile, Que. also increased abundances of functional genes related to the “immune system” and “lipid metabolism”. After WSSV challenge, the cumulative mortality of shrimp decreased with increasing levels of dietary Que., the gene expression of WSSV envelope protein and hemocytes surface receptor protein were down-regulated (P < 0.05), while the gene expression of hemocytes immunity was up-regulated (P < 0.05). In summary, Que. improved the growth performance, enhanced the antioxidant capability and immune response, regulated the composition and structure of intestinal microbiota, and reduced cumulative mortality after WSSV challenge of Litopenaeus vannamei.