Effects of dietary arginine levels on intestinal morphology, digestive enzyme activity, antioxidant capacity and intestinal flora of hybrid snakehead(Channa maculata ♀×Channa argus ♂)

Abstract

The effects of arginine on intestinal shape, digestive enzyme activity, antioxidant capacity, and intestinal flora of hybrid snakeheads Channa maculata♀×Channa argus♂. Five experimental diets were formulated to contain arginine with 2.31%, 2.42%, 2.72%, 2.92%, and 3.12% respectively, and recorded as G1 (control), G2, G3, G4, and G5. Five groups of 50 fish (22.02 ± 0.02 g) for each diet were fed to apparent satiation twice daily for 56 days. The results showed that significantly higher weight gain (WG), specific growth rate (SGR), protein deposition rate (PDR), intestinal somatic indices (ISI), lipase, trypsin, Na+/K+-ATPase, γ-glutamyl transpeptidase, and significantly lower feed coefficient rate (FCR) were observed in fish fed with 2.92% diet compared to 2.31% group (P < 0.05). There was a significant increase of intestinal villus length, villus width and muscular thickness in fish fed with 2.92% and 3.12% arginine diets compared with those in 2.31% group (P < 0.05). The fish fed with 2.92% or 3.12% arginine diets had significantly higher intestinal total antioxidant capacity (T-AOC), catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), glutathione peroxidase (GSH-Px) and lower malondialdehyde (MDA) compared to those in 2.31% group (P < 0.05). High-throughput sequencing revealed arginine supplementation can significantly increase the generation of probiotic bacteria and altered the composition of intestinal microbes. There was a significant increase of the abundance of Firmicutes and Proteobacteria in fish fed 3.12% arginine diets compared with those in 2.31% group (P < 0.05). Based on the WGR, a broken-line regression analysis showed that the appropriate level of arginine in the diet of hybrid snakehead was 2.95% (6.65% of the feed protein).