A LONG-TERM CULTURE OF GIBEL CARP (CARASSIUS AURATUS GIBELIO) IN NET CAGES FOR 340 DAYS: EFFECTS OF DIETARY STARCH ON GROWTH AND GLUCOSE METABOLISM

To study the effects of dietary carbohydrate on growth and glucose metabolism of gibel carp, 5 different diets with 3% (S3), 13% (S13), 23% (S23), 33% (S33) and 43% (S43 starch were formulated for a 340-day trail with 5 sampling times of day 63 (D63, the juveniles fish stage), day 110 (D110, the prophase cultivation period), day 223 (D223, overwintering stage), day 275 (D275, after overwintering stage) and day 340 (D340, the middle and late cultivation period). The results showed that gibel carp at different developmental stages had various starch utilization ability and glucose metabolism. The hindgut amylase activity and sensitiveness were low in the juveniles gibel carp and then increased from the prophase cultivation period. The activities of amylase in hindgut changed with the increased dietary starch level after D63. The GLUT2 mRNA level in gibel carp at D63 among groups were similar, while it increased with the increased dietary starch levels at D110, D275 and D340. The glycolysis was higher than gluconeogenesis in gibel carp at all stages. High glucose-induced lipogenesis was found in gibel carp at D63 and D110. The optimum dietary starch level was 23% for juvenile gibel carp at D63. The dietary starch requirement decreased to 13% for gibel carp at D113. After overwintering of D275, gibel carp showed a compensatory ability to utilize starch with the best growth performance in diet with 43% of dietary starch. At D340, gibel carp exhibited the best growth performance in 33% dietary starch group. The present results indicated that gibel have various abilities of the requirement and utilization of dietary starch at different developmental stages.