Effects of dietary arginine on growth, activity of digestive enzymes, GCN2‐ATF4 signalling pathway and nutritional metabolism‐related gene expression of large yellow croaker ( Larimichthys crocea ) larvae

A 30-day feeding experiment was conducted to elucidate the effects of dietary arginine on growth performance, activity of digestive enzymes, GCN2-ATF4 signalling pathway and nutritional metabolism-related gene expression of large yellow croaker larvae (initial weight: 10.56 ± 0.26 mg). Four isonitrogenous and isolipidic diets with different arginine levels (19.5, 31.0, 39.6 and 48.6 g kg−1 of dry matter) were formulated. Results showed that no significant differences in survival, growth and whole-body proximate composition were observed among dietary treatments. The whole-body arginine content of fish larvae was significantly increased with increasing contents of dietary arginine, and the maximum was observed in larvae fed the diet with 48.6 g kg−1 arginine. However, the contents of other amino acids were not significantly affected. Larvae fed the diet with 19.5 g kg−1 arginine showed higher activity of alkaline phosphatase (AKP) in the intestinal segments (IS) and brush border membranes (BBM) than other groups. The expression of GCN2-ATF4 signalling pathway-related genes (atf4, chop and asns) in the visceral mass of larvae was significantly upregulated by dietary 39.6–48.6 g kg−1 arginine supplementation. Dietary 48.6 g kg−1 arginine significantly upregulated the expression of proteolytic genes (murf1 and glud) in the visceral mass of larvae. Furthermore, the highest expression of genes related to fatty acid β-oxidation (cpt1α) and glycolysis (gk and pk) was observed in the 39.6 g kg−1-arginine group. In summary, those results suggested that dietary arginine had no significant influence on the growth performance of large yellow croaker larvae. However, the arginine level significantly affected the arginine content of whole larvae, activity of digestive enzymes, lipid metabolism and glycolysis of larvae. The GCN2-ATF4 signalling pathway was stimulated by high-dose (31.0–48.6 g kg−1) arginine, maybe due to the antagonistic effect of arginine and lysine. These results might indicate that 19.5 g kg−1 dietary arginine (37.6 g kg−1 dietary protein) could meet the growth requirement of large yellow croaker larvae.