ntroduction
Due to the increasing costs and environmental impacts of fish meal production, insects could prove to be a better raw material for fish feed manufacturing in the future.1 Their high protein content and low resource requirements are key factors in producing sustainable feed.2 With Brabender Instruments it is possible, to extrude fish feed on a small laboratory scale and to optimize the composition of the raw materials as well as the way of manufacturing by analyzing the rheological properties of the finished product.
Material and Methods
Fish Feed manufacturing:
Three batches of fish feed were produced by use of a Brabender twin screw extruder KETSE 20/40 (Table 1 + Figure 1). The fish meal fraction in the raw material blend was 15 %. This fraction was replaced by defatted black soldier fly (Hermetia illucens) larvae meal by 0, 50 and 100 %.
Procedure for the fish feeds digestibility related to its gelatinization properties:
The results of the MVAG measurements (Figure 3) show, that a higher concentration of insect meal increases the degree off cook of the starch, which is directly related to the fish’s digestibility
Conclusion
Trials showed that insect meal can be used as fish meal substitution for fish feed manufacturing. It should be noted, that there are significant influences concerning the extrusion process and that the change of the product properties.
With regard to further investigations, changing of process conditions e.g. variating the extruder screw speed, feed moisture or temperature profile might optimize the product properties as desired. Feeding trials are needed to evaluate the feed acceptance and the nutritional value of the product. Studies indicate, that the nutritional value of black soldier fly larvae meal is lower than fish meal.4 Therefore, higher quantities may be required for a proper diet. Further research is needed in order to improve the omega-three fatty acid spectrum of the fish free product. The addition of micro algae with high omega-three contents might be a solution.
However the extrusion process has to be adapted when fish meal is substituted by insect meal. Should black soldier fly larvae meal gets cheaper than fish meal, it could prove to be a viable option to reduce the environmental impact of aqua culture in the future.