Availability of carbohydrate in nutrition of carp and red sea bream.

The availabilities of a-starch, dextrin, and glucose in the nutrition of carp Cyprinus carpio and red sea bream Chrysophrys major were investigated by comparing the growth and feed efficiency and the changes in rates of absorption (percent absorption per hour) and in blood sugar levels after the administration of carbohydrate. The growth and feed efficiency of carp were highest when fed with the α-starch diet, followed by the dextrin and glucose diets in decreasing order. Red sea bream did not show any significant difference in growth for the various carbohydrate sources, but showed higher feed efficiency when fed with the α-starch diet than with teh dextrin and glucose diets. The percent absorption within the 2-hour period after the administration was highest in glucose, followed by dextrin and α-starch in decreasing order, but the absorptions after that period followed the reverse order. This difference was reflected in the change of blood sugar levels. These findings suggest that the availability of carbohydrate in fish nutrition may be influenced by the difference in percent absorption before and after the 2-hour period, at which time the plasma insulin showed the maximum level.