Impact of Dietary Feeding Levels of Juvenile Red-Tail Catfish () in Land-Based Circular Tank: Insights From Metabolomics and Microbial Analysis.

To investigate the most effective feeding level for red-tail catfish () raised in land-based circular tanks and the impact of feeding levels on at the molecular and omics levels, we conducted a 56-day experiment using the fish fries (16.49 ± 0.44 g). Three groups were established with varying feeding levels: 2% (T2), 3% (T3), and 4% (T4) of body weight per day. We compared conventional growth and physiological parameters, transcription levels of antioxidant activity, transforming growth factor (tgf), inflammatory factors, and lipid metabolism genes as well as intestinal microbiota and metabolomics. Our results showed that the feed conversion rate (FCR) in the T2 group was significantly lower than those in the other groups, but there were no significant differences in specific growth rate (SGR) and weight gain rate (WGR) among the groups. The T2 group had significantly higher level of albumin compared to the T4 group, while total protein (TP) and low-density lipoprotein cholesterol (LDL-C) levels were significantly lower than the T3 group. The T2 group also have significantly higher activities of superoxide dismutase (SOD) and alkaline phosphatase (ALP) compared to the other groups, and both alanine transaminase activity and goblet cells (GCs) were markedly elevated in the T2 group compared to the T3 group. Additionally, the T2 group had the lowest Firmicutes/Bacteroidetes ratio, with an increase in and . The differential metabolites in the T2 group were significantly upregulated in amino acid metabolism and lipid metabolism-related pathways. The expression levels of antioxidant genes, tgf, anti-inflammatory factors, and lipid metabolism genes were all markedly elevated in the T2 group. These findings suggest that the optimal feeding level for was 2% of body weight per day. These results can serve as a guide for the scientific aquaculture of .