Effects of dietary konjac oligosaccharide supplementation on serum immune parameters and intestinal immunity of Schizothorax prenanti

Abstract

The aim of this study was to investigate the effects of dietary konjac oligosaccharide (KOS) supplements on the serum immune parameters, intestine microbiota, and intestine immunity of Schizothorax prenanti. Fish were fed a control diet (basal diet without KOS) or a diet with KOS supplements (0.4% KOS g kg−1 [low-KOS] and 1.6% KOS g kg−1 [high-KOS]. Fish on the high-KOS diet had significant increases in serum alternative hemolytic complement activity, complement 3 content, and nitric oxide content and a significant decrease in malondialdehyde content. Total superoxide dismutase activity was significantly in fish on KOS-supplemented diets, regardless of inclusion level. The lactic acid bacteria levels were significantly increased in fish on the high-KOS diet, while the Aeromonas populations were significantly decreased in fish on the KOS-supplemented diets, regardless of inclusion level. Lysozyme activity in both the mid and distal intestine was significantly enhanced by the high-KOS diet. Only the high-KOS diet significantly increased the acid phosphatase activity in the distal intestine. Regarding immune-related gene expressions, the high-KOS diet was observed to significantly induce the expression of Toll-like receptor 22 in the both anterior and distal intestine. Tumor necrosis factor-alpha mRNA level in the whole intestine was significantly up-regulated in fish on the KOS-supplemented diets, regardless of the inclusion level. The expression of Interleukin 1beta in both mid and distal intestine was significantly promoted by the KOS-supplemented diets, regardless of inclusion level.