The digestive enzyme activity, intestinal microbiota and immune-related genes expression of snakehead fish (Channa argus) juveniles affected by dietary cricket (Gryllus testaceus) meal

Abstract

This study aimed to investigate the potential of using cricket (Gryllus testaceus) meal as the main protein source in fish feed for snakehead fish (Channa argus) juveniles. A 10-week feeding trial was conducted to assess the effects of partial replacement of fishmeal (FM) with cricket meal (CM) on growth performance, digestive enzyme activity, intestinal microbial composition, liver antioxidant capacity, immune response and determine the appropriate replacement FM level with CM in juvenile Channa argus diet. Five isonitrogenous and iso-lipid experimental diets were formulated by replacing 0 %, 15 %, 30 %, 45 % and 60 % of FM with CM, respectively named T0 (control group), T15, T30, T45 and T60 groups. The results demonstrated T45 and T60 showed a significantly decreased feed conversion ratio (FCR) than T0 (P < 0.05). Crude lipid content was significantly higher in T45 and T60 than in T0 (P < 0.05). With increasing dietary CM content, the activities of amylase and lipase were significantly increased in T60 (P < 0.05). At the phylum level, 16S rDNA sequences revealed that Proteobacteria abundance was dominant in all treatments, while Ralstonia abundance had higher significance in T60 than others at the genus level (P < 0.05). The total antioxidant capacity (T-AOC) in liver in T30 and T45 were significantly higher than in T0 (P < 0.05). Glutathione peroxidase (GPx) activities had a significant increase in fish fed groups except T0 (P < 0.05), while malondialdehyde (MDA) content was significantly lower within T45 and T60 than T0 (P < 0.05). The up-regulated gene expression level (IL-1β, IL-10, and HSP70) and down-regulated expression level (IL-8) were showed in all treatments with CM replacement. HSP90 and Iκ-Bα expression levels were increased and peaked in T30 (P < 0.05). According to the results of the current study, in Channa argus diets, FM replacement with CM can be up to 30 % without compromising growth performance, enzyme activities, antioxidant capacity, intestinal microbiota, and immune response.