Effects of Se-chitosan on the growth performance and intestinal health of the loach Paramisgurnus dabryanus (Sauvage)

To determine the effects of Se-chitosan on the growth performance and intestinal health of the loach Paramisgurnus dabryanus, 450 fish (initial mean weight: 5.0 ± 0.2 g) were randomly allocated to 15 PVC tanks and fed diets containing 0 (group C), 0.6 (group T1), 1.2 (group T2), 1.8 (group T3), or 2.4 (group T4) mg/kg Se-chitosan for 60 days. No statistically significant differences were found in growth parameters, including final average weight, specific growth rate (SGR), weight gain (WG), and survival rate between the control and experimental groups. Acid phosphatase (ACP), alkaline phosphatase (ALP), and lysozyme (LZM) activity levels were significantly affected (increasing to ~1389 U/mL, 96I U/L, and 744 U/mL, respectively) when >1.2 mg/kg Se-chitosan was added to the loach diet. The immunoglobulin M (IgM) content increased with increasing levels of Se-chitosan, and was significantly higher in the T4 group than in the control group. Following 16S rRNA sequencing, 296 operational taxonomic units were identified across the control and T3 groups. Alpha diversity analysis showed that species richness and diversity increased with increasing levels of Se-chitosan. Se-chitosan supplementation increased the abundance of Bactroidetes, Cyanobacteria, and Firmicutes, while decreasing the abundance of Proteobacteria, Actinobacteria, and Fusobacteria. Thus, Se-chitosan supplementation might enhance the intestinal health of the loach, and it might therefore be useful as an immunostimulator in loach aquaculture.