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A 2 · 3 factorial design with triplicates examined the interaction between dietary inorganic phosphorus (IP) and phytase on growth, mineral utilization and phosphorus (P) mineralization in juvenile red sea bream. The treatments were three levels of dietary IP supplementation at 0, 2.5 and 5 g kg )1 , either without or with phytase supplementation [2000 FTU kg )1 ; phytase unit is defined as the amount of enzyme activity which liberates 1 micromol of inorganic phosphorus per minute at pH 5.5 and 37°C at a substrate concentration (sodium phytate) of 5.1 mmol L )1 ]. Juvenile red sea bream (IBW = 1.3 g ± 0.1) were stocked twelve fish per tank and fed for 50 days. Growth and feed efficiency were significantly (P < 0.05) enhanced by both dietary P and phytase supplementation. Feed intake and survival rate were not significantly affected by the dietary treatments. Both dietary IP and phytase supplementation significantly increased plasma IP and Mg levels. Concentration of vertebral mineral and scale P was significantly increased by both dietary treatments. A skeletal malformation syndrome of scoliosis occurred in fish fed both non-IP and non-phytase supplemented diet. Interaction between main dietary effects was detected for vertebral Zn, scale P and whole-body ash and Mg content. With regard to growth and other examined productivity traits, phosphorus requirement of juvenile red sea bream can be met if supplemented with 2000 FTU phytase kg )1 or in the absence of phytase, by dietary inclusion of 2.5-5 g kg )1 of IP.

A feeding trial was conducted to evaluate the influence of dietary supplementation of Undaria pinnatifida fucoidan on growth performance and immunological response of juvenile Marsupenaeus japonicus. Four semipurified diets supplemented with graded levels of fucoidan (0.0, 100, 500, and 1000 mg/kg diet) were fed to juvenile shrimp for 8 wk. Each diet was fed to three replicate groups of shrimp. At the end of the feeding trial, enhanced growth performance was generally observed in shrimp fed the fucoidan‐supplemented diets when compared with the shrimp fed the control diet. Significantly higher weight gains, specific growth rates, protein retentions, and lower feed conversion ratios were observed in treatment groups fed the 500 and 1000 mg/kg dietary fucoidan supplementation when compared with the treatment groups receiving 100 mg/kg fucoidan supplementation and the control diet. Total hemocyte counts, phenol oxidase activity, and serum antibacterial activity were also significantly enhanced in shrimp fed diets supplemented with 500 and 1000 mg/kg fucoidan supplementation. These results suggest that U. pinnatifida fucoidan at a dose of 500 mg/kg diet could be used as an immunostimulant and a growth‐promoting dietary supplement for juvenile M. japonicus.

An experiment was carried out to evaluate fermented soybean meal and squid by‐product blend (1:1) (FP) as replacement of fishmeal (FM) for Japanese flounder, Paralichthys olivaceus. Five isocaloric (19 kJ g−1) diets were prepared by replacing 0 (FP0), 12 (FP12), 24 (FP24), 36 (FP36) and 48% (FP48) FM protein with FP. Triplicate groups of juveniles (mean weight of 3.9 g) were delivered the test diets for 8 weeks in a flow‐through sea water system. The results showed that there were no significant differences (P > 0.05) among the growth rates of fish fed FP0, FP12, FP24 and FP36 diets. Growth and nutrient utilization parameters were significantly reduced in fish fed FP48 diet. Although, whole body proximate composition of fish were not significantly affected by the dietary treatments compared to the control; methionine and phenylalanine contents were significantly decreased in FP48 group. Protein retention was also significantly decreased in the similar group of fish. Dietary treatments did not alter most of the plasma metabolites, while some of the health parameters were improved in the replacement groups. Results suggested that FP is a potential candidate for alternative protein ingredient in aquafeed and can replace 36% FM protein in the diet of Japanese flounder.

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