COMPARATIVE STUDY ON THE EFFECT OF DlETARY CORN STARCH CONTENT ON GROWTH, FEED UTILIZATION AND BODY COMPOSITION OF CHINESE LONGSNOUT CATFISH( LEIOCASSIS LONGIROSTRIS GBNTHER)AND GIBEL CARP( CARASSIUS AU RATUS GIBELIO)

Two 8-week growth trials were conducted under similar experimental conditions to study the difference in the dietary carbohydrate utilization for carnivorous and ominivorous fishes by investigating the effect of dietary corn starch content on growth performance of Chinese longsnout catfish(Leiocassis longirostris GÜnther) and gibel carp(Carassius auratus gibelio).Five isonitrogenous and isolipidic diets containing different corn starch content(0, 5%, 10%, 15%, 20% ) were prepared for Chinese longsnout catfish while five isonitrogenous and isolipidic diets containing different corn starch contents(6%, 12%, 18%, 24%, 30% ) for gibel carp1Each diet was fed to triplicatetanks of fish(12 Chinese longsnout catfish per tank,average initial body weight 8.3g;20 gibel carp per tank, average body weight 9.0g) to apparent satiation twice a day1The results showed that, for Chinese longsnout catfish, specific growth rate(SGR) of the fish fed diets containing 5% and 10% dietary corn starch were significantly higher than those of the other three groups(P0.05)1For gibel carp,SGR increased with the increase in dietary corn starch content from 6% to 24% whileFI decreased1FCE of fish fed diet containing 24% corn starchwas significantly higher than those of other groups(P<0.05) 1Body lipid contents of two fishes increased with the increase in dietary corn starch content1In conclusion,the optimal dietary nitrogen-free extraction level for Chinese longsnout catfish and gibel carp was 7.66% and 15.62%,respectively1Gibel carp showed better utilization of corn starch than Chinese longsnout catfish does