Effects of the partial substitution of dietary fish meal by two types of soybean meals on the growth performance of juvenile Japanese seabass, Lateolabrax japonicus (Cuvier 1828)

The effect of partial substitution of dietary fish meal with a high-value soybean meal (HVS) and a commercial soybean meal (CSM) on the growth performance in juvenile Japanese seabass (8.3 +/- 0.2 g body weight) was determined. Nine isonitrogenous (crude protein 44%) and isoenergetic (20 kJ g-1) practical diets replacing 0 (the control), 15%, 30%, 45% and 60% fish meal protein by soybean meal protein (HVS or CSM) were formulated. Each diet was randomly assigned to four replicate cages (1.5 x 1.5 x 2.0 m). Fish were fed twice daily for 10 weeks. Growth was significantly reduced with increased soybean inclusion in fish fed both the soybean sources. Independent of the soybean source used, increased inclusion of soybean meal decreased the growth performance. When the substitution level was 45% or more in CSM and 60% in HVS, the specific growth rate (SGR) and the feed efficiency ratio (FER) were significantly lower compared with the control. These results indicated that CSM protein could substitute for 30% fish meal protein, while the substitution level of HVS protein could be 45%, which did not influence the growth of juvenile Japanese seabass. The higher substitution level for HVS compared with CSM was probably due to better nutritional values.