An eight-week feeding trial was conducted to investigate the effects of dietary andrographolide on the growth performance, antioxidant capacity in the liver, intestinal inflammatory response and microbiota of Monopterus albus. A total of 900 health fish (25.00 ± 0.15 g) were randomly divided into five groups: AD1 (the basal diet) as the control, and AD2, AD3, AD4 and AD5 groups, which were fed the basal diet supplemented with 75, 150, 225 and 300 mg/kg andrographolide, respectively. The results showed that compared with the control group, dietary andrographolide supplementation (1) significantly increased trypsin and lipase activities in the intestine, and increased the weight gain rate but not significantly; (2) significantly increased the levels of glutathione reductase (GR), glutathione (GSH) and glutathione peroxidase (GPx) and the content of in the liver; significantly decreased the contents of reactive oxygen species (ROS) and malondialdehyde (MDA); remarkably upregulated the Nrf2, SOD1, GSTK and GSTO mRNA levels in the liver; downregulated the Keap1 mRNA level; (3) significantly increased the villi length and goblet cell numbers in the intestine, remarkably upregulated the Occludin mRNA level in the intestine, downregulated the Claudin-15 mRNA level; (4) remarkably upregulated the IL-10, TGF-β1 and TGF-β3 mRNA levels in the intestine; downregulated the IL-12β and TLR-3 mRNA levels; (5) significantly decreased the richness and diversity of the intestinal microbioma, increased the percentages of Fusobacteria and Firmicutes and significantly decreased the percentages of Cyanobacteria and Proteobacteria. In conclusion, these results showed that dietary low-dose andrographolide (75 and 150 mg/kg) promoted growth and antioxidant capacity, regulated the intestinal microbioma, enhanced intestinal physical and immune barrier function in rice field eel.

The rising cost of fish meal (FM) in aquaculture feed has prompted the search for alternative protein sources like soybean meal (SBM). However, SBM‐based diets can negatively affect fish growth, lipid metabolism, and intestinal health. One possible solution is to add cholesterol to SBM‐based feeds to mitigate these adverse effects, but the optimal levels and the resulting benefits remain unclear. In this study, the impact of adding cholesterol to low FM and high soybean protein diets on the growth, lipid metabolism, and intestinal health of Monopterus albus was evaluated. Juvenile M. albus (initial body weight of 20.00 ± 0.02 g) were fed a control diet with 42% FM + 22% SBM diet (FM group), 22% FM + 52% SBM diet (SBM group), and the SBM diet supplemented with 5 g/kg or 10 g/kg cholesterol (SBC5 and SBC10 groups, respectively). The results showed that the weight gain rate (WGR) and hepatosomatic index (HSI) were significantly lower in the SBM group compared to the FM group, but WGR increased with the addition of 10 g/kg cholesterol. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities increased significantly in the SBM group, indicating liver stress, but returned to normal levels in the SBC10 group. Cholesterol supplementation also improved serum and liver lipid profiles and significantly increased the contents of total cholesterol (TC) and low‐density lipoprotein cholesterol (LDL‐C) in serum and high‐density lipoprotein cholesterol (HDL‐C) in the liver. In addition, cholesterol supplementation increased the activities of intestinal enzymes (e.g., amylase) and restored the structural integrity of the intestinal lining, including villus height and goblet cell count. Additionally, the SBC10 group exhibited a richer and more diverse intestinal microbiota, with increased abundance of Firmicutes and Bacteroidota. These findings demonstrate that supplementing 10 g/kg cholesterol in a high SBM diet improves growth performance, lipid metabolism, intestinal health, and gut microbiota composition in M. albus . This study provides a practical food‐borne strategy to enhance the use of plant‐based proteins in aquaculture while mitigating their negative effects, contributing to the sustainability of fish farming.

Imidacloprid (IMI), a widely used neonicotinoid insecticide, has raised environmental concerns due to its potential impact on non-target aquatic organisms. This study investigates the effects of IMI exposure on the intestinal immune function of red swamp crayfish (Procambarus clarkii, P. clarkii), focusing on oxidative stress, inflammatory response, and autophagy. The P. clarkii was exposed to different doses of IMI (0, 10.93, 21.86, 43.73, 87.45 μg/L) for 96 h. Our findings reveal that IMI exposure leads to a survival rate of less than 70% when the concentration was 87.45 μg/L at 96 h. Hemolymph LZM and AKP contents were significantly decreased at the medium and high concentrations, and the expressions of hsp70 and nf-κb genes were significantly up-regulated. The expression of the lysozyme gene was significantly down-regulated. Additionally, the activities of SOD, CAT, and GPX were significantly decreased, the contents of MDA were significantly increased, and the gene expressions of CuZnsod, mMnsod, cat, and gpx in the gut were significantly down-regulated after exposure to medium-high IMI. The expression of autophagy-related genes showed that the expressions of beclin1, atg5, atg13, and lc3c genes in the medium- and high-concentration groups were significantly up-regulated. In summary, this study elucidates that medium-high levels of IMI exposure impair intestinal immune function in P. clarkii through mechanisms involving oxidative stress, inflammatory response, and autophagy.