EFFECT OF DIETARY STARCH LEVEL ON GROWTH, FEED UTILIZATION AND HEPATIC GLYCOGEN OF ERIOCHEIR SINENSIS

In order to investigate the utilization of dietary starch by Eriocheir sinensis,seven isonitrogenous (crude protein: 35%) and isolipid (crude lipid: 6%) diets that contained different starch levels (4%, 10%, 16%, 22%, 28%, 34% and 40%) were formulated. Different diets were fed to crabs for 8 weeks. In order to avoid cannibalism, 40 crabs were reared individually in 40 small plastic tanks (25 cm17 cm15 cm)with several holes on the bottom. The results showed that feeding rates of the crabs that were fed with 34%-40% dietary starch were significantly lower than those fed with 4%-16% dietary starch (P0.05). Dietary starch increased specific growth rates of body weight and carapace length. Specific growth rate of body weight reached to the highest at 34% dietary starch while specific growth rate of carapace length was the highest at 22% dietary starch(P0.05). Feed efficiency increased with increasing dietary starch. High dietary starch obtained higher protein retention. Hepatosomatic index of the crabs fed with 16% dietary starch was lower while molting frequency and survival werehigher. Crab body dry matter, protein, lipid and ash were higher at the group fed with higher dietary starch. Hepatopancreatic trypsin activity was higher at 16% dietary starch (P0.05). Liver glycogen content increased linearly with dietary starch (y=0.2268x + 17.256, R2=0.9453, n=7, P0.05). Quadratic regression between specific growth rate and dietary starch showed that optimal dietary starch content for maximum growth of juvenile mitten crab was 25.6%.