Effect of dietary fish meal replacing with rice protein concentrate on growth and body composition of Caspian kutum, (Rutilus frisii kutum, Kamensky, 1901)

In this experiment fish meal was replaced with RPC by levels of 0, 25, 50, 75, and 100%. Diets fed to kutum (initial weight of 340±20 mg) three times daily for 60 days. The highest final weight (1020 mg) and weight gain (670 mg) and the lowest FCR (1.5) were observed in the 50% substitution treatment, which was significantly different from the other treatments (P < 0.05). The survival rate was 100% and the same for all diets. No significant difference was observed in carcass composition (moisture, protein, lipid and ash) between different treatments (P > 0.05). By increasing the amount of rice protein concentrate, the amount of n-3 decreased and the amount of n-6 increased (P<0.05). The ratio of n-3 to n-6 did not change significantly up to the level of 25%, but it showed a significant decrease with the increase of the substitution level. The amount of total amino acid did not change significantly among the treatments with the increase in the concentration level. The highest amount of essential amino acids was related to the 25% treatment, which was significantly different from the control, 50, 75 and 100% replacement treatments. In general, the results of this study showed that rice protein concentrate can be used as a substitute for fish meal up to 50% in the diet without significant change in the growth of Kutum fry. Of course, the quality of carcass fatty acids was not maintained at this level, and the 25% level was more suitable.