Growth, hematological and biochemical indices of common carp Cyprinus carpio fed diets containing corn gluten meal

The effects of replacing fish meal (FM) with corn gluten meal (CGM) on growth and physiological performance were evaluated in common carp (Cyprinus carpio). Six experimental diets were formulated by substituting 0 (control), 20, 40, 60, 80, and 100% CGM protein for FM protein. The concentrations of dietary protein in the experimental diets were 27.8–29% and the P:E ratios were 14.7–15.46 mg/kJ. Eighteen fish with an initial weight of 13.5 ± 0.1 g were allocated to each of 18 circular tanks (450 L) to give triplicate groups for each dietary treatment. The fish were fed to satiation for 8 weeks. At the end of the feeding trial, growth indices, body proximate composition, and hematological and biochemical parameters were measured. Blood samples were taken from six fish in each tank. Final weight and total length were significantly higher in fish fed 100% CGM (27.8 ± 1.2 g and 11.9 ± 0.3 cm) than for those fed the control (22.7 ± 1.4 g and 10.9 ± 0.5 cm) or 20% CGM (22.3 ± 1.2 g and 11 ± 0.4 cm) diets. No effect of FM replacement by CGM was observed for condition factor or hepatosomatic index (P > 0.05). The highest value of protein productive value (14.31 ± 0.65) was observed in fish fed 20% CGM (P < 0.05). There were no significant differences in percentage body moisture and fat, but percentages of protein and ash were significantly different among experimental groups; the highest values of protein (15.6 ± 0.24%) and ash (3.01 ± 0.26%) were recorded in fish fed 40% CGM. For hematological parameters, the highest number of white blood cells (4.1 ± 0.1 × 10³ mm⁻³) was observed in fish fed 100% CGM (P < 0.05). In addition, the highest hematocrit (42.1 ± 0.7%) and triglyceride (294.11 ± 23.82 mg dl⁻¹) were seen in fish fed the diet containing 40% CGM, while 80% CGM gave the highest cholesterol level (204.44 ± 9.0 mg dl⁻¹; P < 0.05). Replacement of FM with CGM had no negative effects on growth and physiological parameters of common carp fingerlings in this short (8 weeks) trial, suggesting that it may be feasible to replace FM with CGM in diets formulated for juvenile common carp.