Insect-based feed blends : effects of extrusion on selected technological and nutritional features

The aims of this study were to examine the effect of extrusion process on Hermetia illucens (BSFL), Tenebrio molitor (YMWL) and Zophobas morio (SWL) blends with or without soybean meal (SBM) addition and to evaluate the impact of extrusion on the in vitro organic matter digestibility (IVD-DM) and in vitro crude protein digestibility (IVD-CP) in insect-based blends. Two blends, for each insect, have been formulated as follows: (i) 50% of corn meal, 25% of insect, 25% of dried carrots meal; (ii) 25% of corn meal; 25% of SBM, 25% of insects, 25% of dried carrots meal. The nutritional content of blends prepared for extrusion with and without SBM were 80 - 81% and 79 - 81% for dry matter; 4.7 - 6% and 3.2 - 4.2% for ash; while 20.8 - 22% and 9 - 11.6% for crude protein, respectively. All these results had no significant difference between the insect’s species. All insect-based blends were characterized by a “good” extrudability and torque value remained always under 2 Nm in all samples. Of note, torque value results seem to be higher when SBM was added to the blend, although this difference was not significant. In this study, at 100°C the highest water removal was in the sample YMWL-based and without SBM, while the lowest was obtained in the sample BSFL-based and with SBM, because as reported in other study, inclusion of plant protein, seems to increased the water- holding capacity. IVD-DM and IVD-CP digestibility had no significant difference before and after the extrusion process and also considering the addition of SBM. In conclusion, it’s possible to use extrusion technology with different insect’s species. The addition of SBM doesn’t have any effects on IVD-DM and IVD-CP, but seems to affect torque value and water removal, but further investigations are needed.