312 Extrusion quality and in vitro digestibility of insect-based feed blends.

Abstract Insects are rich in proteins. Therefore, substituting insects for soybean meal (SBM) in animal feed is a sustainable alternative. However, the effects of including insects in animal feed on the extrudability of the feed blends are not well studied. hence, the objectives of this study are to examine how inclusion of insects in animal feed blends affects (i) the technical quality of extrusion and (ii) in vitro digestibility of dry matter (IVD-DM) and crude protein (IVD-CP) before and after extrusion. To test this, a 3 x 2 factorial experiment was designed with 3 species of insects (Hermetia illucens, BSF; Tenebrio molitor, MW; and Zophobas morio, SW) included in the feed blend with or without SBM. The base feed blends were formulated as: (i) 50% corn meal, 25% insect, 25% dried carrots meal; (ii) 25% corn meal, 25% soybean meal, 25% insect, 25% dried carrots meal. Extrusion of feed blends was performed on a co-rotating, micro-conical twin screw extruder. This process allowed to use insects without or limited pre-drying process, that speed up their utilisation as feed ingredients. The technical quality of extrusion was studied in terms of torque value (TV) and physical characteristics of the extradite. Water removal (WR) was also used as marker of extrusion process. TV is the amount of energy required to move the screws in the extruder. The physical characteristics studied such as perimeter, roundness, form factor and solidity were obtained from stereomicroscope and image analysis software. In vitro digestibility experiments were performed according to the protocol for monogastric animals. Data were analysed using ANOVA in IBM SPSS Statistics for IVD and 2-way ANOVA on SAS for technical quality. The results show that TV remained under 2 Nm for all blends, indicating good extrudability. Neither insect species nor SBM affected the physical characteristics of the extruded feed blends. WR results indicated that the presence of SBM in the extruded blends seems to be able to reduce the water removal from the materials. Finally, the IVD-DM and IVD-CP were not different before and after the extrusion process. These results indicate that inclusion of insects in animal feed has minimal effects on the extrusion of feed and its digestibility, while the co-presence of SBM might be important. The next step is to increase the inclusion of insects beyond the levels used in this study and assess the quality of extrusion.