Effects of protein and lipid sources on the growth and survival of red sea bream Pagrus major and Japanese flounder Paralichthys olivaceus receiving micro-bound diets during larval and early juvenile stage

The effects of dietary protein and lipid sources on growth and survival of the red sea bream Pagrus major (30-days old) and Japanese flounder Paralichthys olivaceus (15-days old) were examined using four zein-microbound diets (MBD) containing the following nitrogen and lipid sources: MBD-1, SBP-1000 (soybean peptides with molecular weights of about 1000) + fish oil calcium soap (FOCS); MBD-2, SBP-3000 (molecular weights of about 3000) + FOCS; MBD-3, soybean protein isolate (SPI) + FOCS; MBD-4, SBP-1000 + stearoyl calcium lactate (SCL). Six groups of the test fish were maintained on the following diets for 30 days; group 1, live food; group 2, 1/2 live food + 1/2 MBD-1; group 3, MBD-1; group 4, MBD-2; group 5, MBD-3; group 6, MBD-4. In the red sea bream, high performance in terms of total length (TL) and body weight gain (BWG) was obtained in groups 1, 2, 3 and 4. However, the fish receiving MBD-3 (group 5) and MBD-4 (group 6) had shorter TL and lower BWG than those receiving the other diets. Regarding the Japanese flounder, high performance in terms of TL, BWG, and survival rate (SR) was obtained in groups 1 and 2. Group 3 receiving MBD-1 gave the BWG and SR close to those of group 2 but lower than group 1. In contrast, groups 5 and 6 receiving MBD-3 or MBD-4 alone had significantly (P < 0.05) shorter TL and lower BWG than groups 1 and 2. The present study thus indicated that soybean peptides with molecular weights of 1000-3000 and FOCS are superior to SPI and SCL as nitrogen and lipid sources of MBD for the red sea bream and Japanese flounder at larval and early juvenile stage.