Bioconversion Potential of Agro-Industrial Byproducts by Tenebrio molitor—Long-Term Results

SIMPLE SUMMARY: Due to the forecasted overpopulation of the globe in the coming decades, the possibility of using nutrients (proteins, fats, vitamins) from sustainable sources such as insects has been discussed extensively. Although insects have been widely consumed in Asian and Latin American countries since ancient times, they are a novel food on the European continent. The first insect-based product that was allowed on the European market in early 2021 was powdered yellow mealworm (Tenebrio molitor), and later, in December 2021, frozen and dried mealworms. Agricultural byproducts are a valuable source of nutrients that can serve as a feed for insect rearing, contributing to better bioconversion of nutrients and promoting insects as a safe protein source. The present study has evaluated the bioconversion potential of yellow mealworm larvae grown on 13 diets composed of different agro-industrial byproducts. During the experiment, the larval weight gain and feed consumption were evaluated to calculate the feed conversion ratio and efficiency of ingested feed, as well as the larval development time. The results show that the best mixes for insect rearing were those that contained rapeseed meal and chicken feed, as they significantly improved the feed conversion ratio and efficiency of ingested larvae feed. ABSTRACT: The aim of this study was to compare the growth performance, feed conversion ratio (FCR), and efficiency of ingested feed (ECI) by larvae of the Tenebrio molitor beetle. The growth and development potential of the yellow mealworm was evaluated by using chicken feed (CF), rapeseed meal (RM), wheat bran (WB), and willowleaf sunflower (WS) to obtain inexpensive and various sources of feed. The results showed that the fastest growth with shorter larval development time (74.7 days) was found for insects fed a WB 100 diet. Regarding the final fresh weight of larvae, the highest values were found for larvae grown on WB diets. However, the lowest FCR (1.53 to 1.59) was found for larvae fed RM diets mixed with CF and on the control diet (CF 100). In most cases, it was found that byproduct diets mixed with CF improve the ECI of mealworms, thus contributing to an efficient bioconversion of byproducts into edible sources of nutrients. Thus, except for pure WS as a feed, these byproducts can be used to grow yellow mealworm larvae and may be added to the versatile list of substrates and feed used by small- and large-scale insect producers.