Residual levels of dietary deltamethrin interfere with growth and intestinal health in Litopenaeus vannamei

To date, few study explored the damage of chronic dietary exposure to the lipophilic pesticide deltamethrin (DM) in aquatic animals, and it remains unclear whether its toxicity and residue levels would be affected by dietary lipid levels. Therefore, the present study aimed to elucidate the interactions between dietary lipid levels and DM levels in the Pacific white shrimp, focusing on growth performance, antioxidant capacity, and intestinal microbiota. DM has excellent insecticidal activity and has been used worldwide. Previous research has shown that environmental DM poses toxicity risks to aquatic animals. Six different diets were formulated to feed shrimp for 6 weeks with two lipid levels (6.96 %, 10.88 %) and three DM levels (0.2 mg·kg^-1, 1 mg·kg^-1, 5 mg·kg^-1), namely LF0.2, LF1, LF5, HF0.2, HF1, HF5, respectively. Each diet was assigned to three net cages with a total of 18 cages (40 shrimp per tank, average weight (0.382±0.001 g), of which 0.2 mg·kg^-1, are grouped in environmental DM control groups. The growth of shrimp was reduced as the dietary DM levels increased. When shrimp were fed a diet containing a high dose of DM, a reduction in their antioxidant capacity was also observed. Enzyme activity and gene expression related to lipid metabolism in hepatopancreas and hemolymph indicated a significant interaction between dietary lipid levels and DM in the lipid metabolism of shrimp. The terms of detoxification-related genes (gst, sult, cyp1a1) were upregulated in shrimp fed the high-dose DM. Additionally, the presence of DM in the diet severely harmed the hepatopancreas and intestinal histological morphology. DM in the diet increased the susceptibility of shrimp to pathogens and induced intestine microbiota dysbiosis, disrupting the balance of inter-species interactions. DM was not detected in the muscle and hepatopancreas of the shrimp after six weeks of exposure. In conclusion, the presence of DM in feed reduced the growth performance and antioxidant capacity of shrimp, damaging intestinal health. DM was rapidly metabolized by shrimp.