Arginine improves growth and health status of post-larval Litopenaeus vannamei by modulating amino acid metabolism and enhancing antioxidative defense

This study investigated the dietary arginine requirement for post-larval Litopenaeus vannamei based on growth performance and hepatopancreatic health indicators. A 25-day feeding trial was conducted. Five iso-nitrogenous and iso-lipidic diets contained graded arginine levels (2.12-2.85%, A0-A4). Increasing dietary arginine significantly promoted growth performance without affecting whole‑body composition, while the highest survival rate occurred in shrimp fed the 2.85% diet. Antioxidant responses were endpoint-dependent: SOD and GPX reached their highest activities at A2-A3 (with A2 showing marked activation), whereas T-AOC and CAT continued to increase and MDA decreased at higher arginine levels. Quadratic regression of SOD activity estimated an optimum at approximately 2.51%. Expression of arginine metabolism genes (agm, nos) and antioxidant genes (gpx, sod) was significantly upregulated in A2, whereas protein synthesis‑related genes were strongly activated in A4. Metabolomic profiling identified 141 differential metabolites, with L‑hydroxyarginine and DL‑proline upregulated and creatine downregulated in A4. In parallel, γ‑aminobutyric acid (GABA) and S‑adenosylmethionine (SAM) contents increased, indicating modulation of neurotransmission and methylation. Enrichment analysis showed significant effects on arginine and proline metabolism, glycerophospholipid metabolism, and GABAergic pathways. Correlation and network analyses suggested that elevated arginine improves growth and antioxidative capacity by reinforcing amino acid, phospholipid, and energy metabolism and supporting neuromodulation. In conclusion, integrating regression-estimated optima for antioxidant-related indices with growth and survival outcomes within the tested range suggests that the recommended dietary arginine requirement for post-larval Litopenaeus vannamei is approximately 2.51-2.85%, which promotes growth and survival, supports hepatopancreatic health, enhances antioxidant capacity, and modulates amino acid and lipid metabolism.