Jaana M. Sorjonen

As insect farming is becoming more popular in Europe and in the US, the use of food industry by-products in insects’ feed is drawing more attention. However, it is still unclear how to maximise the use of by-products in the feeds while meeting the nutritional requirements and maintaining profitable rearing yields with the current production technology. In this study, we conducted an experiment in Finnish small-scale cricket farming and laboratory conditions to determine whether five diet treatments, including by-product diets with barley mash and turnip rape, modify the overall fresh yield (kg), development time and feed conversion rate of the house crickets (Acheta domesticus). We discovered that the diets differed in the overall fresh cricket yield (kg) but not in the development time or the feed conversion rate of the crickets. The diets with a high proportion of by-product decreased the price of the feed but at the same time reduced the yield. Based on our results, complex by-product diets with the by-product proportion of 20-41% are the most suitable for house cricket rearing.

The use of food industry by‐products in insect feeds has gained increasing attention recently. However, the understanding of how well the economically valuable edible insect Ruspolia differens (Serville) (Orthoptera: Tettigoniidae) can grow and develop with plant‐based by‐product feeds is currently lacking. It is important to determine the nutritional requirements, especially protein demand, of this species before developing artificial feeds for mass‐rearing. We reared R. differens with four control diets and 12 plant‐based by‐product diets in which the major protein source came from food industry by‐products, including potato‐protein, barley mash, barley feed, turnip rape, a mix of broad bean and pea, and a mix of potato, carrot, and apple. We asked whether the performance (development time, survival, and weight), feed conversion, and fatty acid composition and content differed among diet treatments. Furthermore, the 12 experimental by‐product diets were designed to reach six protein levels. We found that R. differens can be reared with various by‐product diets, but development time, survival, and weight differed among diets. Barley feed, barley mash, and potato protein diets seem to be good options for rearing, and potato glycoalkaloids do not affect the performance of R. differens. Individuals fed on the various by‐product diets also differed in their fatty acid composition and content. Increasing protein levels in diet up to 17% enhanced growth, development time, and survival, but no further enhancements were seen when fed diets with protein levels higher than this. The high protein levels decreased feed conversion rate. Our results can be valuable for designing feeds for insect mass‐rearing technology. The use of food industry by‐products in the diets for R. differens could increase the re‐use of local resources and enhance circular economy.

Edible insect rearing could provide one alternative for protein production by having a smaller environmental impact than traditional livestock farming due to insects’ ability to convert organic side streams. Currently, the insect rearing industry utilizes soybeans as a major source of protein in the feeds. Protein-rich by-products of food industry could be used to replace them in insect feeds, but it is not known if they also meet the insects’ nutritional requirements. Our study evaluated the growth performance of two widely used edible cricket species, Acheta domesticus and Gryllus bimaculatus (Orthoptera: Gryllidae), on 18 experimental diets. The experimental diets included commercial chicken feeds and cricket diets, where soybean was partly and completely replaced with by-products from food industry: potato protein, barley mash, barley feed, compressed leftover of turnip rape and mix of broad bean and pea on three levels of protein. We found that the high- and medium-protein turnip rape and barley mash diets produced the highest yield and an increase in all performance variables. Overall, the high- and medium-protein diets produced the highest yield, growth and fastest development. Our results showed that by-products of food industry could be utilized as a part of the cricket feeds and thus advance the goals of circular economy.