Effects of fish oil on growth kinetics and lipid accumulation in black soldier fly larvae

The main purpose of this study is to characterise how substrate lipid content affects growth kinetics of black soldier fly (BSF) larvae. Growth curves of larvae were characterised in substrates composed of chicken feed supplemented by 0-30% fish oil, and lipid content and fatty acid composition of the prepupae were quantified to examine up-take and assimilation of fish oil by the larvae. Increasing contents of fish oil resulted in reduced specific growth rates, reduced weight of the prepupae, and increased mortality. The prepupae had similar lipid contents at 0-20% fish oil, while 30% fish oil increased the lipid content of prepupae. In contrast, the fatty acid composition of the prepupae showed a strong dependency on substrate fish oil content, indicating that the larvae increased their uptake of fish oil with increasing fish oil content. C16-C22 fatty acids were bioaccumulated from the fish oil, but particularly C20 and C22 fatty acids were apparently also shortened or further metabolised. Microbial fermentation products rapidly accumulated in the substrates, and substrate lipids and carbohydrates were preserved and remained available for the larvae throughout their growth period. These results point out that although BSF larvae can utilise high contents of substrate lipids, it may be at the expense of reduced growth performance, and with limited effects on the composition of their biomass.

Automated summary

The main purpose of this study is to investigate how substrate lipid content affects the growth kinetics of black soldier fly larvae. The results show that increasing fish oil content in the substrate leads to reduced growth rates, decreased weight of the prepupae, and increased mortality. Although the larvae can utilize high levels of substrate lipids, it may negatively impact their growth performance and have limited effects on the composition of their biomass.