OPTIMAL DIETARY STARCH LEVEL FOR JUVENILE FURONG CRUCIAN CARP

To investigate the optimal dietary starch level for juvenile Furong crucian carp, fish meal and casein and the mixture of fish oil and soybean oil (1:1) were used as dietary protein and lipid source to formulate seven isonitrogenous (35%) and isolipid (8%) experimental diets containing different corn starch levels (6%, 12%, 18%, 24%, 30%, 36% and 42%) for a 61-day trial. The results showed that weight gain, specific growth rate and feed efficiency increased first and then tended to be stable with increased dietary corn starch (P0.05), and that there were no significant differences between groups fed with 18%42% dietary corn starch (P0.05). Protein retention efficiency enhanced with increased dietary corn starch (P0.05) and fish fed with 30% and 42% dietary corn starch had higher protein retention efficiency than those fed with 6% and 12% dietary corn starch (P0.05). Plasma glucose concentration had no difference between groups (P0.05). Plasma triglyceride concentration increased with higher dietary corn starch (P0.05). Plasma total cholesterol concentration was significantly higher in 30% dietary corn starch group than other groups (P0.05). Intestine amylase activity and muscle glycogen significantly increased with elevated dietary corn starch level (P0.05). Hepatic glycogen was significantly higher in the 36% corn starch group than others (P0.05). Broken-line analysis based on specific growth rate (SGR) indicated that the optimal dietary starch level was about 27.47% for juvenile Furong crucian carp.