Soybean meal improves the physical quality of extruded fish feed

Partial replacement of FM with either SBM or WF improved the physical quality of feed ill terms of breaking force and durability, bulk density was elevated and radial expansion reduced. Inclusion of WF increased the motor load, die pressure and SME of the WF1 diet compared to the FM and SBM diets, resulting in significantly longer pellets and higher bulk density. Extrusion of the WF2 diet with a less shearing screw configuration in combination with reduced screw rotation gave SME comparable to the energy consumption used during the production of the FM and SBM diets. The new processing conditions caused a significant reduction in length and diameter. and hence increased bulk density. Breaking force corrected for the diameter of the pellet was significantly higher for the WF2 diet produced with lower shear and screw rotation compared to the other three feeds produced under the same extruder conditions. The overall conclusion from the experiment was that durability and breaking force of extruded fish feed was significantly improved by inclusion of soy, regardless of previous heat treatment of this feed ingredient. (C) 2008 Elsevier B.V. All rights reserved.