Life on a piece of cake: performance and fatty acid profiles of black soldier fly larvae fed oilseed by-products

Abstract

The oilseed crops Crambe abyssinica and Camelina sativa produce oils rich in erucic acid and n-3 polyunsaturated fatty acids (PUFA), respectively. After pressing the oil, a seed cake remains as a protein-rich by-product. Edible insects may convert this seed press cake and the defatted seed meal produced from it into insect biomass suitable for animal feed. Black soldier fly larvae (BSF, Hermetia illucens) can grow on a wide range of organic waste types, but may be hindered by excess protein or the plant toxins characteristic for these two oilseed crops, i.e. glucosinolates and their breakdown products. We tested the effects of 25, 50 and 100% oilseed by-product inclusion in the diet on survival, development, biomass production and fatty acid composition of BSF larvae. Larval performance on diets with up to 50% camelina by-product or 25% crambe by-product was similar to performance on control diet (chicken feed), and decreased with higher inclusion percentages. Larval fatty acid profiles differed significantly among diets, with larvae fed press cake more distinct from control than larvae fed seed meal. Larvae fed camelina press cake had more α-linolenic acid, whereas larvae fed crambe contained most oleic acid. The n-6:n-3 PUFA ratio decreased with increasing proportion of by-product, especially on camelina diets. Lauric acid content was highest in larvae fed 100% camelina meal or 50% crambe meal. These results indicate that BSF larvae can be successfully grown on diets with camelina or crambe oilseed by-products, and that the resulting larval n-6:n-3 PUFA ratio is favourable for animal feed. However, the fate of glucosinolates and their derivatives remains to be determined, to guarantee chemical safety of camelina- or crambe-fed BSF larvae for animal feed.