Growth performance, feed utilization, and body composition of Nile tilapia (Oreochromis niloticus L.) fed with differently heated soybean-meal-based diets

This study was undertaken in order to determine the effect of feeding heat-treated, defatted soybean meal (SBM) on growth, feed utilization, and body composition of Nile tilapia (Oreochromis niloticus). A control diet (SBM0) of 378 g kg(-1) crude protein with 18.4 kJ g(-1) gross energy was formulated, and three diets identical to the basal diet were autoclaved for 10, 20, or 30 min. The autoclaved diets were named SBM10, SBM20, and SBM30, respectively. Each diet treatment was applied to triplicate groups of 30 fish (2.45 +/- A 0.03 g) per tank (120 l). The fish were hand fed to satiation four times daily for 45 days. At the end of the feeding trial the fish fed with the SBM30 diet had significantly (P < 0.05) higher weight gain and protein efficiency ratio than those fed with the other diets. No feed-related mortality was observed during the whole experimental period. Heating SBM for 30 min reduced trypsin inhibitor activity (TIA) and increased apparent protein digestibility (APD), and indicated significant differences (P < 0.05) among various treatments. No significant differences were found in carcass moisture, lipid, and ash of fish fed with different experimental diets. An increase in the body protein content of fish fed with diet SBM30 was significantly (P < 0.05) higher than in all other experimental groups. The results of this study seem to indicate that autoclaving the SBM for 30 min improved its nutritional value in practical feeds for Nile tilapia fingerlings.