Modulation of nutrient composition of black soldier fly (<i>Hermetia illucens</i>) larvae by feeding seaweed-enriched media

<div><p>Black soldier fly (<i>Hermetia illucens</i>) larvae are a promising source of protein and lipid for animal feeds. The nutritional composition of the BSF larvae depend partly on the composition of the feeding medium. The BSF lipid profile in part mimics the feeding media lipid profile, and micronutrients, like minerals and vitamins, can readily accumulate in black soldier fly larvae. However, investigative studies on bioconversion and accumulation of nutrients from media to black soldier fly larvae are scarce. Here we show that inclusion of the brown algae <i>Ascophyllum nodosum</i> in the substrate for black soldier fly larvae can introduce valuable nutrients, commonly associated with the marine environment, into the larvae. The omega-3 fatty acid eicosapentaenoic acid (20:5n-3), iodine and vitamin E concentrations increased in the larvae when more seaweed was included in the diet. When the feeding media consisted of more than 50% seaweed, the larvae experienced poorer growth, lower nutrient retention and lower lipid levels, compared to a pure plant based feeding medium. Our results confirm the plasticity of the nutritional make-up of black soldier fly larvae, allowing it to accumulate both lipid- and water-soluble compounds. A broader understanding of the effect of the composition of the feeding media on the larvae composition can help to tailor black soldier fly larvae into a nutrient profile more suited for specific feed or food purposes.</p></div

Most abundant Non-Protein Nitrogen Compounds (μmole g^-1, dry matter) of black soldier fly larvae grown on increasing inclusions of brown algae in feeding media.

<p>Most abundant Non-Protein Nitrogen Compounds (μmole g^-1, dry matter) of black soldier fly larvae grown on increasing inclusions of brown algae in feeding media.</p

Mineral retention (% added minerals recuperated in larvae) of black soldier larvae grown on increasing inclusions of brown algae in feeding media.

<p>Mineral retention (% added minerals recuperated in larvae) of black soldier larvae grown on increasing inclusions of brown algae in feeding media.</p

Proximate-, amino acid- and fatty acid composition of feeding media used for the black soldier fly larvae growth trial.

<p>Proximate-, amino acid- and fatty acid composition of feeding media used for the black soldier fly larvae growth trial.</p

Fatty acid composition (area %) and total fatty acids (FA, % of dry weight) of black soldier fly larvae grown on increasing inclusions of brown algae in feeding media.

<p>Fatty acid composition (area %) and total fatty acids (FA, % of dry weight) of black soldier fly larvae grown on increasing inclusions of brown algae in feeding media.</p

EPA concentration and retention.

<p>The concentration of eicosapentaenoic acid (EPA, as % of lipid) in the black soldier fly larvae increased with increased concentrations of EPA in the feeding media, but the retention of EPA decreased dramatically with inclusion of more than 50% brown algae (BA) in the feeding media. Figures show (A) EPA concentrations (% of total fatty acids) of feeding media and black soldier fly larvae with 0–100% of a plant-based feeding media replaced with ground brown algae; and (B) percent of EPA in feeding medium retained by the insect larvae. The BA0 group is not included in the graphs or the calculations, as EPA levels in the larvae as well as in the feeding media was below limit of quantification (0.01 g kg^-1).</p

Growth of larvae.

<p>By increasing the inclusion of brown algae (BA) in the feeding medium, the black soldier fly larvae had reduced growth and feed intake. Figures are showing mean weight of individual larvae (wet weight) per crate by the end of the trial (A); kg larvae (wet weight) produced per crate during the trial (B) and total feeding media consumed/feed intake of the larvae (feeding medium added minus residue at end of trial) (C). BA: brown algae.</p

Total amino acid composition (% of crude protein) of black soldier fly larvae grown on increasing inclusions of brown algae in feeding media.

<p>Total amino acid composition (% of crude protein) of black soldier fly larvae grown on increasing inclusions of brown algae in feeding media.</p

Mineral- and sterol composition of feeding media used for the black soldier fly larvae growth trial (all results on dry matter basis).

<p>Mineral- and sterol composition of feeding media used for the black soldier fly larvae growth trial (all results on dry matter basis).</p

Proximate composition (%, dry weight) and dry matter of black soldier fly larvae (% wet weight) grown on increasing inclusions of brown algae in feeding media.

<p>Proximate composition (%, dry weight) and dry matter of black soldier fly larvae (% wet weight) grown on increasing inclusions of brown algae in feeding media.</p