Effects of dietary L-arginine or N-carbamoylglutamate on intestinal mucosal morphology and intestinal flora of hybrid snakehead Channa maculata (♀)×C. argus (♂)

This experiment was conducted to investigate the effects of dietary arginine or NCG on intestinal mucosal morphology and intestinal flora of hybrid snakehead Channa maculata (♀)×C. argus (♂). A total of 450 C. maculata (♀)×C. argus (♂) with an initial weight of (22.02±0.02) g were selected. They were randomly divided into three groups of three replicates, each with 50 fish, and fed three experimental diets: basal diet, diet supplemented with 0.60% L-arginine (Arg) and diet supplemented with 0.03% N-carbamylglutamate (NCG). The feeding period was 56 days. Compared with the control group, adding 0.60% Arg to the diet significantly increased the final weight and specific growth rate of C. maculata (♀)×C. argus (♂) (P<0.05), adding 0.60% Arg or 0.03% NCG significantly increased the protein deposition rate of C. maculata (♀)×C. argus (♂) (P<0.05), and significantly decreased the feed coefficient (P<0.05). Compared with the control group, the contents of isoleucine, glutamate and lysine in whole fish in NCG group were significantly increased (P<0.05). Compared with the control group, the contents of arginine and leucine in whole fish of C. maculata (♀)×C. argus (♂) in Arg and NCG groups were significantly increased (P<0.05), but there was no significant difference in other amino acids (P>0.05). Compared with the control group, the addition of Arg or NCG to the diet could significantly increase the thickness of the midgut and hindgut muscle layer and the width of the midgut villus in the C. maculata (♀)×C. argus (♂). The thickness of the hindgut muscle layer in the NCG group was significantly greater than that in the control group and the Arg group (P<0.05). In each experimental group, the structure of intestinal mucosa and muscularis was clear and compact, and the mucosal villi were abundant. In the control group and Arg group, a small amount of gap between the epithelium and lamina propria was widened, but there was no obvious abnormality in the NCG group. The addition of arginine to the diet could significantly improve the species richness of the intestinal flora of C. maculata (♀)×C. argus (♂), and the Chao index and Ace index were significantly higher than those of the control group and the NCG group (P<0.05). Compared with the control group, the abundance of Firmicutes and Proteobacteria was significantly increased in the NCG group, but the abundance of Fusobacterium was significantly decreased in the NCG group, differing significantly from the Arg group (P<0.05). Research shows that the addition of Arg to the feed is better than the addition of NCG in terms of growth performance, but adding NCG to the diet can significantly increase the abundance of beneficial bacteria such as intestinal Firmicutes and maintain the stability of the intestinal environment, with effects superior to those of Arg supplementation.