Effect of Dietary Cornstarch Level on The Growth Performance of Japanese Seabass (Lateolabrax japonicus) in Grow-Out Phase

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A 10-week growth trial was conducted to investigate the effect of dietary cornstarch levels on the growth performance, body composition, liver/muscle glycogen, and selected serum biomarkers, of Japanese seabass in grow-out phase. Six isonitrogenous and isolipidic diets containing graded levels (0%, 6%, 12%, 18%, 24%, 30%) of cornstarch were fed to Japanese seabass (initial weight 343g). Weight gain (WG) significantly increased up to 18% with increasing dietary cornstarch, and then reached a plateau. There was no significant difference in WG between fish fed 18%, 24%, or 30% cornstarch (P>0.05). Based on WG, the optimal dietary cornstarch level of Japanese seabass estimated by second-order polynomial model was 27.0%. Body protein and lipid content as well as total cholesterol and triglycerides in serum showed similar trends, i.e. increasing at first and then reaching a plateau despite increasing levels of dietary cornstarch. Ash content decreased at first and then reached a plateau with increasing dietary cornstarch. Hepatosomatic index and liver glycogen significantly increased with increasing dietary cornstarch (P<0.05) while muscle glycogen, the condition factor was not influenced by dietary treatments. Serum glucose significantly increased with increasing dietary cornstarch and then decreased (P<0.05). Results of this study suggest the provision of adequate dietary cornstarch (>18%) could improve the growth performance of Japanese seabass and the optimal dietary cornstarch level is 27.0% during grow out phase.