We evaluated the effect of a diet containing insect meal and insect oil on nutrient utilization, tissue fatty acid profile and lipid metabolism of freshwater Atlantic salmon (Salmo salar). Insect meal and insect oil from black soldier fly larvae (Hermetia illucens, L.; BSF), naturally high in lauric acid (12:0), were used to produce five experimental diets for an eight‐week feeding trial. 85% of the dietary protein was replaced by insect meal and/or all the vegetable oil was replaced by one of two types of insect oil. A typical industrial diet, with protein from fishmeal and soy protein concentrate (50:50) and lipids from fish oil and vegetable oil (33:66), was fed to a control group. The dietary BSF larvae did not modify feed intake or whole body lipid content. Despite the high content of saturated fatty acids in the insect‐based diets, the apparent digestibility coefficients of all fatty acids were high. There was a decrease in liver triacylglycerols of salmon fed the insect‐based diets compared to the fish fed the control diet. This is likely due to the rapid oxidation and low deposition of the medium‐chain fatty acid lauric acid.

With the fast growth of today's aquaculture industry, the demand for aquafeeds is expanding dramatically. Insects, which are part of the natural diet of salmonids, could represent a sustainable ingredient for aquaculture feed. The aim of the current study was to test how a partial or total replacement of dietary fishmeal with insect meal affect gene responses involved in inflammation, the eicosanoid pathway and stress response in Atlantic salmon (Salmo salar L.) in isolated head kidney leukocytes after exposure to bacterial or viral mimic. Insect meal (IM) was produced from black soldier fly (BSF, Hermetia illucens) larvae. Seawater Atlantic salmon were fed three different diets for 8 weeks; a control diet (IM0, protein from fishmeal and plant based ingredients (25:75) and lipid from fish oil and vegetable oil (33:66); and two insect-meal containing diets, IM66 and IM100, where 66 and 100% of the fishmeal protein was replaced with IM, respectively. Leukocytes were isolated from the head kidney of fish (n = 6) from each of the three dietary groups. Isolated leukocytes were seeded into culture wells and added either a bacterial mimic (lipopolysaccharide, LPS) or a viral mimic (polyinosinic acid: polycytidylic acid, poly I: C) to induce an inflammatory response. Controls (Ctl) without LPS and poly I: C were included. The transcription of interleukins IL-1β, IL-8, IL-10 and TNF-α were elevated in LPS treated leukocytes isolated from salmon fed the three dietary groups (IM0, IM66 and IM100). The inflammatory-related gene expression in head kidney cells were, however, not affected by the pre-fed substitution of fish meal with IM in the diet of salmon. Gene transcriptions of PTGDS and PTGES were neither affected by LPS, poly I: C or the experimental diets fed prior to cell isolation, while salmon fed with IM showed a lower expression of LOX5. The gene expression of TLR22 and C/EBP-β were down-regulated by the LPS treatment in the cells isolated from salmon fed insect-based diets (IM66 and IM100) compared to fish fed the IM0. Similarly, the leukocytes challenged with LPS and isolated from fish fed with IM66 and IM100 down-regulated the expression of Mn-SOD, GPx1, HSP27 and HSP70 compared to salmon fed IM0. In general, these results suggested that replacement of fishmeal with IM in the diets of Atlantic salmon had no effect on the transcription of pro-inflammatory genes in the head kidney cells. There was, however, an effect of dietary IM on the transcription of antioxidant and stress related genes in the leukocytes.

A major challenge for development of sustainable aquafeeds is its dependence on fish meal and fish oil. Similarly, it is unwanted to include more plant ingredients which adds more pressure on resources like arable land, freshwater and fertilisers. New ingredients that do not require these resources but rather refine and valorise organic side streams, like insects, are being developed. Increasing evidence indicates that using insect ingredients in aquafeeds are a sustainable alternative and considerable progress has been made on this topic in the past years. The aim of this chapter is to present a comprehensive and systematic analysis of the data available on the impact of insects in aquafeeds. Systematic search, collection and selection of relevant literature from databases such as Web of Science and NCBI was performed. The literature search enabled 91 scientific papers from peer-reviewed journals, comprising a dataset of 415 experimental diets, including 35 different aquatic species and 14 insect species to be included in this meta-analysis, covering what we consider a close to complete representation of credible publications on this topic. Information on aquatic species, insect species, dietary composition (amino acids, fatty acids, proximate composition) and performance outputs (growth performance indicators and nutrient digestibility) were included in the construction of the dataset. Regression models and principal component analyses were performed on the meta-data. The results from the meta-analysis revealed a great degree of variation in the maximum threshold for insect inclusion in aquafeeds (from 4 to 37%) based on subgroups of trophic level of aquatic species, insect species used, statistical method and the output parameter. Overall, a maximum threshold of 25-30% inclusion of insects in aquafeeds for uncompromised performance is suggested. Reduction in protein digestibility, imbalanced amino acid profile and increasing levels of saturated fatty acid were identified as major factors limiting higher inclusion of insects in aquafeeds.

The production of food is an intensive source of environmental impact. In aquaculture, one source of impact is solid waste, which contains high concentrations of minerals, other nutrients, and metals. The larvae of Hermetia illucens are capable of consuming this material, but applying technology that is based on these larvae for managing waste streams, like those from aquaculture, requires careful examination of safety risks. A study is performed examining the growth performance of larvae that were fed on solid aquaculture waste. Subsequently, a thorough analysis of safety risks from inorganics, with detailed the results on microelements that have previously received little attention in the literature, is performed to serve as a guideline for how to assess the safety of waste streams such as these. Findings confirm existing results in the literature that Cd is bioaccumulative, but also that other elements, including Hg, Mn, and especially K, are bioaccumulative. To the authors’ knowledge, this is the first research where the accumulation of Ag is also tested. The results of these tests are explained within the context of regulations in various countries where Hermetia illucens is cultivated, serving as a reference for practitioners to rigorously screen out high risk feed streams that they may consider using as feed sources. It is intended that these references and the demonstrated accumulation of a range of elements motivate comprehensive industry safety practices when evaluating new feed sources.

Insect protein has the potential to become a sustainable feed ingredient for the rapidly growing aquaculture industry. In the European Union, insect derived protein is placed under the same legislation as processed animal proteins (PAP). It is therefore of interest to develop methods for regulatory use, which unambiguously identify the species origin of insect-based ingredients. We performed (i) total protein quantification of insect samples using the traditional nitrogen-to-protein conversion factor of 6.25 and the sum of anhydrous amino acids, (ii) quantitative amino acid profiling and (iii) high-throughput tandem mass spectrometry to describe and differentiate 18 different commercial-grade insect meal samples derived from Hermetia illucens (8), Tenebrio molitor (5), Alphitobius diaperinus (3) and Acheta domesticus (2). In addition, we investigated and compared different protein extraction and digestion protocols for proteomic analysis. We found that irrespective of sample preparation, shotgun proteomics in combination with direct spectral comparison were able to differentiate insect meal according to their taxonomic classification. The insect specific spectral libraries created in the present work can in future be used to develop more sensitive targeted methods of insect PAP identification and quantification in commercial feed mixtures.

Although the correlation between polyunsaturated fatty acids (PUFA) and the production of pro- and anti-inflammatory metabolites is well documented, little is known about the simultaneous effect of different PUFA on the production of cyclooxygenase and lipoxygenase metabolites. The present research examines the association between different omega-3 (ω-3) and omega-6 (ω-6) PUFA and the release of four cyclooxygenase and six lipoxygenase metabolites in cell medium by human umbilical vein endothelial cells (HUVEC). The different combinations of ω-3 and ω-6 PUFA were prepared according to a full 2⁴ factorial design that enables studying not only the main effects but also the different interactions between fatty acids. In addition, interactions diagrams and principal component analysis were useful tools for interpreting higher order interactions. To the best of our knowledge, this is the first report addressing the combined effect of ω-3 and ω-6 PUFA on the signaling of prostaglandins, prostacyclins, leukotrienes and resolvins by HUVEC.