Aquaculture depends on fishmeal (FM) as a major protein source, but sustainability concerns and rising costs necessitate alternative feeds. The potential use of medicinal plants, particularly fenugreek, as a dietary source can benefit carp farming, especially cyprinids. The present study intends to investigate the impact of FGM on growth performance, antioxidant defence, intestinal function, and fillet quality of the carp. Especially, investigated the effects of graded dietary inclusion of FGM (0%, 25%, 50%, 75%, 100%) as FM replacement on the growth, physiology, and nutritional quality of Cyprinus carpio.
Fish fingerlings (77 ± 9.5 g) were fed isonitrogenous diets (35% crude protein) for eight weeks. Growth performance, feed utilization, organosomatic indices, hematological and serum biochemical parameters, digestive and antioxidant enzymes, histology, carcass composition, and fillet amino/fatty acid profiles were evaluated after the feeding trial. Results from quadratic regression analysis revealed revealed that moderate inclusion levels (~45–55%) improved weight gain (y = -1.14535E−4x2+0.006x+4.413) and specific growth rate (y = 0.91625+1.39773E−4x−3.34565E−6x2) peaking at 50% inclusion. Digestive enzyme activities (amylase, protease) were elevated in FGM25 and FGM50 groups, while antioxidant enzymes (SOD, CAT, GPx) increased across all FGM-fed groups, enhancing oxidative stress tolerance. Hematological and biochemical values remained within normal ranges. However, slight reductions in RBC counts were noted at lower and higher inclusions. Histological examination confirmed normal intestinal and hepatic structures at moderate inclusion, while high inclusion showed mild alterations. Fillet composition analysis indicated improved amino acid and fatty acid profiles, particularly essential amino acids and unsaturated fatty acids in partial inclusion. Overall, partial replacement of FM with FGM at ~50% is optimal for enhancing growth performance, digestive and antioxidant efficiency. This shows the potential of FGM as a sustainable functional feed ingredient in carp aquaculture.