Insects as future food - nutrient requirements and manipulation of whole-body composition in Tenebrio molitor larvae

Black Soldier Fly Larvae (BSFL, Hermetia illucens), yellow mealworms (MW, Tenebrio molitor) and house crickets (HC, Acheta domesticus) are the most common production systems insects reared as an alternative protein source for human food or in livestock feeds. However, the nutrient composition, particularly of larval insects (BSFL and MW), varies significantly. This review will focus on the protein nutritional quality of these species, as well as describing how body composition of MW can be manipulated. These three insect species contain relatively high concentrations of protein (34-72%) and have reported digestibility which varies widely (48-99%). Digestible indispensable amino acid scores (DIAAS) for these three species are at best 75-92%, each with a different limiting indispensable amino acid. Both protein content and digestibility vary between species but also within species due to different feeds and product processing. The administration of exogenous Juvenile Hormone to MW feed causes a large and favourable increase in protein and decrease in fat content, thereby demonstrating the potential for MW nutrient composition to be manipulated to provide a higher value feed ingredient. A similarly agriculturally positive impact on MW nutrient composition, but also growth characteristics, can also be achieved by independently manipulating the individual macro- and micro-nutrient composition of MW's feed. This demonstrates use of feeds with varying nutrient content, could potentially be used to differentially alter protein to fat ratios in MW and increase the total yield of protein. This would represent an important step in improving the commercial viability of mealworms as an animal feed.