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Extruded soybean meal(ESBM) was evaluated as a protein source for partial replacement of fish meal(FM) in diets of juvenile Litopenaeus vannamei. In the control diet(Diet 1), FM protein was replaced with increasing dietary levels of ESBM(4.28%, 8.40%, 12.62%, 16.82%, and 25.26%) at 10%, 20%, 30%, 40%, and 60% levels(Diets 2 to 6, respectively). An eight-week feeding trial was conducted on 720 juvenile shrimp(0.67 g ± 0.01 g mean initial weight), and nutrient digestibility of the six diets was determined. ESBM could replace 20% of FM without causing a significant reduction in growth of shrimp, but other dietary treatments strongly affected whole body composition. Crude protein content of the whole body fed Diet 6 was significantly lower than that fed Diet 2(P < 0.05), while crude lipid content of the whole body fed Diet 5 or 6 was significantly higher than that fed Diet 2(P < 0.05). Protein digestibilities of Diets 5 and 6 were significantly lower than that of Diet 1(P < 0.05). Digestibility of lipids ranged from 96.97% in Diet 6 to 98.34% in Diet 3, whereas dry matter digestibility decreased with increasing replacement level. This study indicates that 20% FM replacement with ESBM in the basic diet containing 40% protein and 30% FM is optimal for juvenile L. vannamei.
In the control diet (Diet 1), the FM protein was replaced with increasing dietary levels of ESBM (4.28%) was used as a protein source for partial replacement of fish meal (FM) in diets of juvenile Litopenaeus vannamei , 8.40%, 12.62%, 16.82%, and 25.26%) at 10%, 20%, 30%, 40%, and 60% levels (Diets 2 to 6, respectively) ESBM could replace 20% of FM without causing a significant reduction in growth of shrimp, but other dietary treatments strongly affected whole body composition. Crude protein content of the whole body fed Diet 6 was significantly lower than that fed Diet 2 (P <0.05), while crude lipid content of the whole body fed Diet 5 or 6 was significantly higher than that fed Diet 2 (P <0.05) . Protein digestibilities of Diets 5 and 6 were significantly lower than that of Diet 1 (P <0.05). Digesti bility of lipids ranged from 96.97% in Diet 6 to 98.34% in Diet 3, but dry matter digestibility decreased with increasing replacement level. This study shows that 20% FM replacement with ESBM in the basic diet containing 40% protein and 30% FM is optimal for juvenile L. vannamei.