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The effects of fish meal (FM) replacement with graded level of soybean meal (SBM) on growth performance, feed utilization, survival rate and body composition were investigated in juvenile tiger grouper, Epinephelus fuscoguttatus (initial body weight 13.9 ± 0.65 g). Six experimental diets were formulated to contain 50% crude protein, 16% crude lipid and 365.8 kcal/100g feed with SBM replacing FM protein at 0% (SM 0), 10% (SM 0), 20% (SM 20), 30% (SM 30), 40% (SM 40) and 20% with phytase (SM 20P) replacement levels. At the end of the ten-week feeding trial, there were no significant differences detected in terms of growth performances (weight gain and specific growth rate), feed conversion ratio (FCR) and survival rates of fish fed with the control diet (SM 0), SM 20, SM 30 and SM 20P. Net protein utilization of fish fed SM 20P was higher than those fed with other diets suggesting an improved utilization of nutrients with phytase addition in the diet. Replacements of FM protein with SBM at 10% and 40% have resulted in significantly lower growth and poorer FCR than other replacement levels. Survival rates remain high (≥90%) throughout the trial. Whole-body proximate composition of the fish was significantly affected by the inclusion of SBM in the diets. It can be concluded that 20% -30% of FM protein replacement with SBM is recommended and addition of phytase in the SBM-based diet should be considered to improve nutrient utilization of tiger grouper juvenile.

The present study was conducted as a continuation of our previous study on the effects of fish meal replacement with soy bean meal, SBM in the diets of tiger grouper, Epinephelus fuscoguttatus which revealed the possible level of fish meal protein replacement of 30% with positive effect of phytase supplementation in one of the test diet. In the present study, all experimental diets with SBM inclusion (10%, 20%, 30%, 40% replacement levels) were supplemented with phytase and fed to juvenile tiger grouper with initial body weight of 44.57 ± 0.28 g for eight weeks. Apart from the effects on growth performance, diet utilization and fish whole-body composition, apparent digestibility coefficient of diets was also measured. Similar findings to our previous experiment were observed in the present study. Diet SM40P (40% replacement level) had produced the poorest growth performance and feed conversion ratio (FCR). However, it was observed that FCR of SM40P was improved when compared to SM40 (without phytase) in our previous experiment. Other than that, SBMbased diets were performed as good as the control diet in terms of growth, feed utilization and survival rate. Replacement of fish meal did not significantly influence body composition, except for whole body lipid content in SM40P. In general, dry matter and protein apparent digestibility coefficients (ADC) of the test diets were influenced by SBM inclusion in the diets. However, crude lipid ADC was very high in all dietary treatments indicating efficient utilization of dietary lipid by juvenile tiger grouper. The findings of the present study confirmed that SBM can be used to replace FM at a level of up to 30% and supplementation of phytase in SBMbased diets is recommended to improve the diet performance.

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The aquaculture of decapod crustaceans is expanding continuously to supply protein source for human consumption. Therefore, intensive research is necessary to improve the quality of the feeds in decapod crustacean farming. Decapod crustaceans are slow feeders, and dietary inclusion of plant proteins reduces their intakes on the feeds. Dietary supplementation of chemoattractants (CA) (to reduce food searching duration) and feeding stimulants (FS) (to stimulate ingestion) is therefore necessary to