Growth and Feed Efficiency of Adult Yellowtail Fed Extruded Pellet Diets with Two Lipid Levels and Raw-fish Diets

Abstract

Feeding experiments were conducted to establish the effective use of extruded pellet (EP) in the adult yellowtail, Seriola quinqueradiata. Fish were fed two types of commercial EP, medium fat type (CL 23%, EP-MF) and high fat type (CL 28%, EP-HF) during July to December. Two feeding trials were carried out during the years 2000 and 2001. Growth performance and feed utilization in these fish were compared with those of fish fed raw-fish diet. In the summer season when the water temperature rises above 24°C, the daily growth rates (DGR), daily feeding rates (DFR) and feed efficiencies (FE) in fish fed on the two pellet types were not different from those in fish fed on raw-fish diet. On the other hand, DGR of fish fed EP were significantly lower than that of fish fed the raw-fish diet in the fall season. Though the DFR in the EP-fed groups were significantly lower than that of the raw-fish fed group in the fall season, FE was not significantly different. Therefore, it was suggested that proper feeding regimes had to be developed to improve growth of fish fed EP in the fall season. There was no growth difference between yellowtail fed high and medium dietary lipid levels, thus no clear conclusion was made which lipid level is suited for adult yellowtail.