Effect of dietary types on the utilization of practical diet by yellowtail

Abstract

This experiment was conducted to examine the effect of dietary types on the utilization of practical diet by yellowtail Seriola quinqueradiata. Three types of diet were prepared by pelleting the same dietary ingredients such as brown fish meal, soybean meal, and feeding stimulants: single moist pellets (MP), steam pellets (SP), and extruded pellets (EP). They were fed to fingerling yellowtail at a restricted feeding rate for 50 days in 0.8 ton aquaria. Although a relatively long time was needed to feed SP, there were no significant differences in the growth rate, feed efficiency, protein efficiency ratio, and nutrient retention rates among the three dietary groups. Furthermore, the dietary treatment scarcely affected their blood characteristics and body composition, although feeding SP and MP resulted in a large intestinal size and a low carbohydrate digestibility, respectively. These results indicate that yellowtail can utilize SP as effectively as MP and EP under the present feeding conditions.