EFFECTS OF DIETARY RATIO OF FISH MEAL AND RAPESEED MEAL ON THE GROWTH AND FEED UTILIZATION IN GIBEL CARP(CARASSIUS AURATUS GIBELIO)

Effects of replacement of fish meal with rapeseed meal on the growth and feed utilisation were investigated in juvenile gibel carp (Carssius auratus gibelio). Three groups of fish were fed with each of five groups of diets supplemented with different concentrations of rapeseed: 0, 20%, 40%, 60% and 80% of total dietary protein. The experiment was carried out in a recirculation system at 26.5-29.5℃ (mean 28.5℃) for 8 weeks. The results showed that the growth rate of the fish decreased significantly when the rapeseed protein accounted for 40%, or higher, of the total dietary proteins. The feed intake was not affected by the concentration of rapeseed. The digestion rate of the dry matter and protein was significantly lower only when the concentration of rapeseed protein was 80% of the total dietary proteins. The digestion rate of energy was the lowest when rapeseed protein accounted for 40% of the total. Feed conversion efficiency decreased significantly when the dietary rapeseed protein concentration was 20% or higher. The protein and energy retention efficiency decreased when dietary rapeseed protein concentration was 40% or higher. The body energy and fat content reached the highest values when the fish was fed with the diet containing 40% rapeseed protein. The body protein level was lowest at the rapeseed protein concentrations of 60% and 80%, while the fat content was highest at 20%. Based on the data we suggest that the optimal concentration of rapeseed protein should be 20% in the diet for gibel carp.