October 16, 2023 - Insects are a natural part of the diets of wild salmon when they are in rivers. Insects are also making their way into the diets of farmed salmon. When Nofima scientists wanted to test the species of insect called black soldier fly in salmon feed, it was therefore natural to measure the effects on salmon parr, which are young, freshwater salmon.
Using the whole insect in feed
Currently, not all of the insect is used in feed. The larvae are processed into the three fractions of oil, meal and stick water. It is the latter two fractions that were tested in feed for juvenile fish. The meal is rich in protein, and stick water is thought to be rich in bioactive components. The properties these fractions have in fish meal are already well known. From a bio economic perspective, it is therefore desirable to test and utilise this resource from insects in salmon feed.
Nofima scientists and a master's student at NMBU measured the effect on digestion and growth in juvenile fish during the growth phase from approximately 20 to 85 grams.
At Nofima in Bergen, feed technologists produced trial feed in which they added 10 percent insect meal and different levels of stick water from insects. The insect ingredient was compared in feed with similar protein content and replaced half of the fish meal in a control diet. The feeds were given to salmon parr held in trial tanks at Nofima's Sunndalsøra research station.
The goal was to find any differences in digestion and growth in fish that were fed feed based on insects with an increasing content of stick water.
Grew just as well
The trials showed that salmon grew just as well and had just as good digestion when their diet contained stick water from insects. With 10 percent insect meal in the feed, the fish also grew just as well as fish that received the control feed.
"The trial shows that there is no problem in salmon having at least 10 percent insect meal in their feed. Based on the positive effects of the stick water fraction from fish meal, we cannot rule over that this fraction from insects would have had a positive effect under other conditions. In any case, it is an important side stream to safeguard for optimal utilisation of insects as feed for fish", says Nofima's Andre Sture Bogevik.
In the project, the level of the mineral manganese was also investigated. The EU has threshold values for the content of manganese in the finished feed for farmed fish, and insects contained naturally high levels of this. The trial showed that the fish excrete the mineral and do not absorb more in the body than if the meal did not contain high levels of manganese. Nor did the mineral lead to any deformities or have a negative impact on growth.
Aqua director at Innovated, Elon Kvamme, is satisfied with the result:
"We are delighted to observe results aligned with the internal research we have carried for the past years at Innovafeed. The growth results pave the way for the widespread use of insect protein in the salmon industry, as a sustainable traceable and performing ingredient".
Research on low-trophic raw materials
The research was conducted in the Millennial Salmon project, which is funded by the Research Council of Norway. The research is published in the master's thesis of Erika Marie Hanson at the Norwegian University of Life Sciences (NMBU) from 2022 entitles 'effects on growth and welfare of Atlantic salmon parr, feed diets with 10 percent BSFL meal, with different inclusions of BSFL stick water.'
Nofima senior scientist Katerina Kousoulaki is the project manager for the Millennial Salmon project, which focuses on optimising and using heterotrophic micro algae and insect meal as replacements for large parts of fish oil and sot in salmon feed.
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