Enrichment of polyunsaturated fatty acids in black soldier fly larvae (Hermetia illucens) fortified with squid liver oil

Abstract

Black soldier fly larvae (BSFL; Hermetia illucens) are known as an alternative feed for livestock, but their lack of polyunsaturated fatty acids (such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) makes it less valuable. To overcome these problems, BSFL substrate (chicken feed) was fortified with squid liver oil (SLO) at five different concentrations (0, 2.5, 5, 10, and 20%). The growth rate, feed conversion, and nutritional content of BSFL were evaluated at day 15 of rearing. Of the five concentrations, SLO 5% showed the highest growth increase (25.82-fold) among the other treatments (20.63-22.98-fold; P<0.05). The fortification of SLO 5% did not result in differences in survival and feed conversion of larvae compared to larvae fed the control substrate. By rearing BSFL in a substrate containing SLO 5%, the lipid content of the larvae was 32% higher than that of larvae fed the control substrate (P<0.05). The accumulation of lipids was faster in the substrate containing SLO 5% (33.20% for 8 days) than in the control substrate (24.36% for 15 days). The control group of BSFL contained no DHA or EPA, but after rearing on the SLO 5% fortified substrate, the larvae contained DHA at an average level of 2.99 g/100 g lipid and EPA was 2.68 g/100 g lipid. Harvested larvae from SLO 5% treatment was within safe levels of Pb, Cd, As, and Hg (840, 370, 860, and 26.7 μg/kg, respectively), under the EU threshold for animal feed. Based on our results, it concluded that BSFL enriched with PUFAs, DHA and EPA can be considered as important nutritional components of animal feed without excessive heavy metals accumulation by feeding SLO in an appropriate amount.