Over the last year, the BSF group has conducted exciting experiments as part of the Happy Salmon project. We received big batches of two species of macroalgae (Ulva and Saccharina) for the Nordic SeaFarm in Dingle, to be used as feed substrate for rearing BSF larvae. The algae was mixed with brewery spent grains, provided by Train Station Brewery in Knivsta and vegetable waste, ensuring a nutritiously balanced diet for the larvae. Interestingly, the larvae grew quite well in this blend substrate and achieved a high body protein (40%), while the fat content was considerably lower than our larvae usually are (< 15%), making this larval biomass a good feed ingredient.
The frass fertilizer obtained in these experiments also had interesting properties, having > 80% of organic matter and a NPK ratio of 3/1/3. However, the most exciting results regarding this frass fertiliser was the composition of beneficial microorganisms, stimulated by the presence of the algae in the larval diet. Moreover, the frass container plant hormones, including auxins, gibberellins and cytokinins, which are important regulators of plant growth and metabolism. These novel results are being investigated and assessed now to see how different plant species can benefit from frass when it is applied in the soil.
As a next step, the larvae produced with the macroalgae and brewery spent grains are being pressed and defatted, and then used as a nutritious feed ingredient for the production of fish feed. Skretting, a global leader in sustainable aquaculture nutrition, in Norway will use this feed in salmon growth trials. We believe that this BSF larvae-derived ingredient can be considered a more sustainable feed ingredient for aquaculture. Fingers crossed for interesting results to come!