Dietary N-carbamylglutamate Supplementation Enhances Muscle Quality in Triploid Crucian Carp (Carassius auratus) by Regulating Muscle Development, Collagen Synthesis and Antioxidant Capacity.

This study evaluated the effects of dietary supplementation with graded levels of N-carbamylglutamate (NCG) on growth performance and muscle quality in triploid crucian carp (TCC). Six isonitrogenous (35.00% crude protein), isolipidic (6.20% crude lipid), and isoenergetic (17.80 MJ/kg) diets were formulated with NCG inclusion levels of 0, 0.125, 0.25, 0.50, 1.00, and 2.00 g/kg diet. After an 8-week feeding trial, NCG supplementation significantly improved feed intake but did not affect other growth parameters. Notably, muscle quality was markedly enhanced in NCG supplemented. Muscle crude protein content increased significantly at 0.25 g/kg NCG level. Free amino acid analysis revealed increasing trends in glycine and aspartic acid levels, with aspartic acid content significantly elevated in the 0.25, 0.50, 1.00, and 2.00 g/kg groups, peaking at 0.25 g/kg. The 0.25 g/kg NCG group exhibited significantly lower drip loss and higher muscle hardness and adhesiveness. Histological examination indicated increased muscle fiber density in the 0.25 g/kg group. Gene expression analysis showed significant upregulation of muscle development markers (myod, myog, mrf4, myhc), collagen synthesis genes (col1a1, col1a2), and antioxidant-related genes (keap1, sod, cat, gpx, gsta) in the 0.25 g/kg NCG group. In conclusion, dietary NCG supplementation at 0.25 g/kg effectively enhances muscle protein content, structural integrity, flavor profile, water-holding capacity, and antioxidant potential in TCC, providing a scientific basis for its application in quality-focused aquaculture.