Effects of Dietary Protein and Temperature on Growth and Flesh Quality of Songpu Mirror Carp

The study was conducted to demonstrate the effects of dietary protein and water temperature on growth and flesh quality of Songpu mirror carp (Cyprinus carpio) at an initial weight (165.24±5.08) g. Practical diets were formulated to contain five protein levels (29.12%, 31.46%, 34.49%, 38.17%, and 40.13%), and each diet was randomly assigned triplicate groups of 15 fishes at three temperatures (18°C, 22°C, and 26°C) in the recirculation system. Fishes were fed twice daily to apparent satiation for 56 days. Results indicated that fishes had higher weight gain rate at 22°C and 26°C than that at 18°C (P<0.05), but there were no significant differences between 22°C and 26°C (P>0.05). Based on the weight gain rate, dietary protein level 29.12% could meet the requirement of the body at 18°C, 22°C, or 26°C. Crude protein, crude lipid, moisture and ash of muscle had no significant differences among those treatments (P>0.05). pH (after 24 h) of muscle was the highest at 18°C and the lowest at 22°C (P<0.05), but no differences were observed among different protein level groups at each temperature (P>0.05). No significant differences on shear force, water holding capacity, collagen, glycogen and lactate among all the treatments were found (P>0.05). It was concluded that when C. carpio fed to apparent satiation, the growth mainly depended upon temperature. Dietary protein could not significantly affect flesh quality, but temperature significantly affected pH of muscles. A dietary protein level 29.12% could meet the requirement of the body at 18°C, 22°C, or 26°C.