Dietary N-Carbamylglutamate Modulates Muscle Growth, Nutrient Composition, and Metabolic Profiles in Danzhou Chickens

This study evaluated dose-dependent effects of dietary N-carbamylglutamate (NCG) on muscle growth, nutrient composition, and metabolic profiles in Danzhou chickens. A total of 480 one-day-old female Danzhou chicks were randomly assigned to diets supplemented with 0, 400, 800, or 1200 mg/kg NCG for 35 days and slaughtered at 35 days of age. NCG at 400–800 mg/kg improved growth performance, increased crude protein and free amino acids (arginine, methionine), and altered fatty acid composition in a muscle-specific manner, with increased breast-muscle MUFA and decreased leg-muscle arachidonic acid and DHA; total PUFA did not differ. Histological analysis showed that NCG increased leg-muscle fiber cross-sectional area and Feret diameter, accompanied by a reduction in fiber density. Mechanistically, NCG altered the mRNA expression of IRS2, IGF1, MyoG, AKT1, and FOXO1 in a manner consistent with modulation of the IGF-1/IRS2/PI3K/Akt/FoxO1 axis. Metabolomics suggested an association with purine metabolism; however, this finding is exploratory and does not establish causality. Integrated multi-omics revealed crosstalk between purine and lipid metabolism. Among the doses tested, 800 mg/kg produced the largest response for several endpoints; however, no formal dose-optimization model was fitted, and the optimal dose remains to be determined. The 1200 mg/kg dose did not further improve most endpoints, indicating a nonlinear dose response. This study provides the first multi-omics evidence demonstrates that NCG modulates muscle growth, nutrient composition, and metabolic profiles in indigenous chickens through coordinated regulation of anabolic signaling, purine metabolism, and lipid remodeling. Direct meat-quality measurements were not performed; therefore, effects on eating quality, technological quality, oxidative stability, and consumer preference remain to be established.