Effect of Dietary .ALPHA.- and .BETA.-Starch on Growth of Juvenile Striped Jack and Yellowtail.

Abstract

This experiment was conducted to investigate the availability of dietary gelatinized starch (ƒ¿-) and raw starch (ƒÀ-) as an energy source in diet for juvenile striped jack and yellowtail. Both fish were fed three kinds of diets containing either 10% ƒ¿- or ƒÀ-starch, and a mixture of both starch at 5% each. The gelatinized ratio (GR) of these diets was 100, 16.6, and 50.0%, respectively. The highest daily feed consumption was observed in fish fed the diet containing 10% ƒÀ-starch in both experiments. This value was decreased when the content of ƒ¿-starch in diet increased. The fish fed the diet containing 10% ƒÀ-starch in both experiments showed the lowest percent gain, feed efficiency, and PER. Crude lipid contents in whole body of fish fed diets containing 10 % ƒÀ-starch alone were lowest among the treatments in both experiments. These results indicated that a supplement of ƒÀ-starch alone as a dietary carbohydrate source is not effectively utilized for growth of striped jack and yellowtail. On the other hand, good performances were observed in fish fed the diet containing 10% ƒ¿-starch and a mixture of both starch at 5% each. Thus, these results suggested that the GR of diet for both striped jack and yellowtail should be above 50% in order to achieve better growth performances, at least half of dietary carbohydrate must be ƒ¿-starch at a supplemental level of 10%.