The natural predispositions of Arctic charr (Salvelinus alpinus (Linnaeus, 1758)), a species associated to the Holarctic realm, to sustain and recover from extended periods of feed restriction and growth depression during the winter were cautiously explored in an aquaculture context. The degree to which a growth recovery is achieved upon refeeding is governed by the timing and the intensity of the restriction and the coping mechanisms occurring under the rearing conditions provided. Advantages for aquaculture are reduced labor, feed, and phosphorus load. We investigated the effect of (1) a pilot-scale cyclical restriction-refeeding sequence over three size classes (Pre-experiment) and (2) the inclusion of dietary nucleotides during recovery on growth and feeding metrics, and sustainable profitability value (Experiment). Despite a feed reduction of ∼30%, no clear effects on growth were observed, translating in savings of 1.84 CAD per kg of produced fish. Incorporation of dietary nucleotides during the recovery phase resulted in improved growth and feed conversion efficiency and created an upward shift of digestive organs allometries. Nucleotides exclusion after 60 days subsided all the above. Overall, feed restriction induced net positive outcomes that increased the sustainable profitability value of the feeding strategy. We suggest that severe restriction leading to low adiposity and nucleotide supplementation are required for the full expression of compensatory growth in Arctic charr.

The bioconversion of hatchery residues (HR; unmarketable chicks, eggs and eggshells) by black soldier fly larvae (BSFL) offers an alternative to conventional rendering. Fermentation of HR improves microbiological quality and odours but results in carbohydrate-deficient diets. This study assessed the potential of BSFL to bioconvert fermented and unfermented HR diets and evaluated the impact on resulting larvae and frass. Diets included a control (Gainesville), unfermented HR, and fermented HR (14 days, 0.3 % ferment, 25 % lactose, dry basis), with or without 13 % potato residues (dry basis) as a carbohydrate source. The BSFL (n = 800 5-day post-eclosion neonates) were reared in triplicate per treatment (0.6 g dry diet/larva). Microbiological analyses were performed on diets, larvae, and frass. Yield and bioconversion rate were significantly lower for unfermented (60 +/- 7 g; 5 %) and fermented HR (19 +/- 4 g; 2 %) than for the control (209 +/- 18 g; 14 %). Fermentation effectively reduced initial coliform loads to values (< 2 log cfu/g) below those of the control (4 log cfu/g) and unfermented HR (5 log cfu/g) but failed to control spore-forming Clostridium spp. (8 log cfu/g in diets; 9 log cfu/g in larvae). Larvae and frass from the control exhibited higher contamination with Salmonella spp. and Listeria monocytogenes (4-5 log cfu/g) than those from unfermented HR (3 log cfu/g). These findings indicate that HR can support BSFL rearing, though further composition and texture optimisation is required. While fermentation enhances initial substrate quality, post-harvest treatments of larvae remain essential to ensure microbial safety.

The conventional management of hatchery residues (HR) poses environmental issues and health risks for handlers. This study evaluates the potential of fermentation to reduce pathogens and odors in HR, enabling them to be recovered into feed using black soldier fly. This saprophagous edible insect is valued for its ability to efficiently bioconvert organic residues into high-quality biomass. Due to the low carbohydrate content of HR, whey permeate was added at lactose inclusion levels of 0, 5, 15, 25, and 35% (dry basis) to optimize fermentation. Using a commercial ferment starter culture (0.3%, wet basis), HR were fermented under semi-anaerobic conditions for two weeks. Fermentation metrics, including pH, microbiological loads (total aerobic mesophilic, presumptive lactic acid bacteria, coliforms, Escherichia coli), volatile fatty acids, and volatile organic compounds, were monitored at days 0, 3, 7, and 14. Optimal stabilization was achieved with lactose inclusion of 15 to 35% after 7 days, which reduced pH (<5.3), increased lactic (87.82 mg/g) and acetic (20.28 mg/g) acid production, and decreased coliform and Escherichia coli counts below detection limit (1.7 log cfu/g). The production of compounds associated with unpleasant odors was also limited. The use of a ferment did not result in a greater reduction of coliform counts, the initial loads of lactic acid bacteria (> 7 log cfu/g) being sufficient to initiate spontaneous fermentation. However, ferment was found to be efficient in heated HR. These findings demonstrate the effectiveness of fermentation for stabilizing HR, highlighting its potential for integration into insect bioconversion systems.

In fish, polyunsaturated fatty acids (PUFAs) are essential structural elements in cellular membranes, participate in pathway regulation and act as important energy storage sources for optimum growth performance. However, they are also highly susceptible to peroxidation and thus potential oxidative damage. Omega-3 fatty acid content can vary among individuals and populations of fish and can therefore modulate their health status or resistance to oxidative stress. Our objective was to modulate $ \Sigma $ omega-3 content in fish through different diets and estimate its impact on growth performance, overall fatty acid composition, oxidative stress parameters and antioxidant activity. We conducted experiments on juveniles (1+) of four salmonid groups: Arctic charr (Salvelinus alpinus), brook charr (Salvelinus fontinalis) and their reciprocal hybrids. We found that growth performance in the four groups was negatively affected by high dietary fatty acid content. The content of thiobarbituric acid reactive substances (TBARS, a marker of lipids peroxidation) significantly rose in Arctic charr when fed the omega-3-rich diet. It was also observed that individuals with high docosahexaenoic acid and low $ \Sigma $ omega-6 content had lower TBARS content. Consequently, high omega-3/omega-6 ratios were accompanied by lower oxidative stress levels. This supports the utilization of omega-3/omega-6 ratios as a marker of the ability of fish to modulate oxidative stress both in the wild and in an aquaculture context. This will further help to predict responses to environmental or nutritional modifications.

The extensive use of veterinary antibiotics in livestock production is a growing concern, particularly in terms of environmental sustainability and health security. This review presents the case of veterinary antibiotic use and regulations in Canada before exploring a potential novel avenue for agricultural antibiotics waste up-cycling. The impact of the widespread use of antibiotics in animal husbandry is reviewed, and the dissemination routes of antibiotic residues and antibiotic-resistant bacteria from farms to the environment are explored to identify potential weaknesses in the management of veterinary antibiotics. The presence of antibiotic residues in livestock products and manure poses significant challenges, as these residues contribute to the development of antibiotic-resistant bacteria, which poses a threat to both the environment and health. The review examines the fate of animal waste contaminated with antibiotics in the environment, exploring the impact of management practices on antibiotic degradation and their persistence in soil and water systems. Additionally, the potential risks to human and animal health are addressed, emphasizing the links between antibiotic residues in the environment and the rising threat of antimicrobial resistance. The last part of this review focuses on exploring how up-cycling veterinary antibiotic residues in insects for feed and fertilizers could contribute to mitigating these risks. Overall, this review calls for more integrated solutions that balance the need for antibiotics in animal agriculture with the prevention of environmental contamination and the antibiotic resistance threat, while meeting the rising demand for animal proteins, highlighting the need for more region-specific surveillance programs.

Hatchery residue valorisation through fermentation and black soldier fly larval bioconversion offers a promising alternative to conventional management. However, assessing the technical and economic feasibility of such systems is essential before implementation. While financial planning tools already exist, they require adaptation to specific production models, scales, and regional contexts. This study aimed to develop a feasibility assessment tool designed for a Quebec-based valorisation system. The tool incorporates two production models: centralised (110 tonnes per week (tpw)) and decentralised (10, 15, or 25 tpw), while evaluating the use of two fermentation co-products (dry or liquid whey permeate), two integration levels for reproduction (in-house or external supply of neonates), and two packaging options (bulk or retail). In total, 32 theoretical production scenarios were analysed. Infrastructure and equipment requirements were derived from supplier quotations and a pre-engineering report for black soldier fly processing facilities. The tool estimates operational costs, including labour, inputs, energy, and maintenance, as well as financial considerations such as loan repayments for capital expenditures. Revenues from the sale of dried larvae (pet food market) and composted frass (organic fertiliser) are included, enabling the calculation of annual profits based on the production model and site capacity. Although secondary processing scenarios are excluded, the tool provides a comprehensive overview of the costs associated with implementing and operating such a system. It considers regional factors, including the availability of inputs and the challenges posed by Quebec’s northern climate, making it a relevant tool for producers exploring alternative ways of managing hatchery residues.

Larval frass from insects which consists of larval excrement, exoskeleton, and undigested diet, is a rich source of organic material and microorganisms. Despite its potential value, research on frass valorisation in agriculture is limited. In this study, single-layer agar (SLA) and double-layer agar (DLA) in vitro bioassays were conducted to evaluate the effect of water-based black soldier fly larvae (BSFL) frass extracts from two different diets on the growth of six plant pathogens: Alternaria solani, Botrytis cinerea, Fusarium oxysporum, Phytophthora capsici, Rhizoctonia solani and Sclerotinia sclerotiorum. The results showed that frass extract from Gainesville house fly diet strongly or completely inhibited the growth of all tested plant pathogens in both SLA and DLA bioassays, while frass extract from fruit/vegetable/bakery/brewery diet strongly inhibited the mycelial growth of A. solani, B. cinerea, and S. sclerotiorum, and moderately inhibited the mycelial growth of P. capsici in both bioassays. For both diets and bioassays, 0.22 mu m microfiltered frass extracts which are free of microorganisms showed generally no effect on the growth of the pathogens indicating that growth inhibition is caused by frass-inhabiting microorganisms. Both SLA and DLA bioassays revealed strong antagonistic effect of microorganisms inhabiting BSFL frass against the plant pathogens B. cinerea, A. solani, R. solani, P. capsici, F. oxysporum and S. sclerotiorum. Moreover, the study showed the impact of the BSFL diet on the antagonistic effect of frass extract. In future work, the antagonistic effect of frass extracts against the above-mentioned pathogens will be tested in vivo. BSFL frass could eventually find applications for the control of plant diseases.

This review examines the use of insect meal (IM) as a substitute for fishmeal (FM) in fish feeds within the past decade. While global interest in this alternative is growing, research on its effects on fish digestibility, blood parameters, and economic performance has been limited. Meta-analysis on the apparent digestibility coefficient revealed a negative effect summary on dry matter (-0.92) and crude lipid (-0.51), although the difference between the two groups was relatively minor. However, a positive effect summary was reported in the apparent digestibility of crude protein (0.12), suggesting a potential advantage in the utilization of protein by fish fed with IM-containing diets. Whereas meta-analysis on fish blood parameters demonstrates varying effects summary, necessitating further research. Analysis of economic performance revealed an overall better economic performance in the IM diet with an effect summary of-0.08 for feed cost and 0.00 for the economic profit index. Overall use of IM in aquafeed shows promise in improving feed quality and fish performance, potentially becoming a sustainable alternative to traditional FM. Recommendations include exploring IM's impact on fish blood parameters through more investigations. Shifting focus from traditional measures to markers directly linked with fish health and immune response can provide more precise insights. Moreover, exploring various components of IM, such as lipids and functional elements like chitin, through simplified breakdown methods, can significantly enhance our comprehension of their nutritional value. Analyzing how each part influences fish health could pave the way for a sustainable and efficient alternative to FM in aquaculture.

The conventional management of hatchery residues is associated with greenhouse gas and unpleasant odor emissions, the presence of pathogens and high disposal costs for producers. To address these issues, on-farm alternatives like composting, fermentation, and insect valorization are promising approaches. This study aims to characterize hatchery residues and define critical quality thresholds to identify effective processes for their management. Hatchery residue samples were collected bi-monthly over a year (N = 24) and were analyzed for proximate composition (dry matter, ash, energy, crude protein, crude lipid, crude fiber, carbohydrates), pH, color (L*a*b*, Chroma) and microbiological loads (total aerobic mesophilic counts, coliforms, lactic acid bacteria). Volatile fatty acid composition was also measured (N = 8). Significant correlation coefficients were found between TAM and LAB loads and residue characterization (pH, chroma, crude fibers, carbohydrates, and temperature). On a dry matter basis, residues were high in energy (2498 to 5911 cal/g), proteins (21.3 to 49.4 %) and lipids (14.6 to 29.1 %), but low in carbohydrates (0 to 15.3 %) despite temporal fluctuations. Ash content varied widely (8.6 to 49.1 %, dry matter) and is influenced by eggshell content. Microbiological loads were high for total aerobic mesophilic bacteria (6.5 to 9.1 log cfu/g), coliforms (5.4 to 8.5 log cfu/g) and lactic acid bacteria (6.7 to 9.0 log cfu/g). Valorization of hatchery residues on the farm will depends on the optimization of effective upstream stabilization processes. The critical points are discussed according to the valorization potentials that could be implemented on the farm from composting to upcycling by insects.

This study investigated the effect of black soldier fly larvae (BSFL) frass derived from BSFL reared on a diet composed of fruit/vegetable/bakery/brewery residues (FVBB diet) and on the Gainesville diet (GV diet) on the development of tomato (Solanum lycopersicum) Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici (FOL). Tomato plants were grown in a substrate inoculated with FOL that was amended (10%, v:v) or not (control) with either a commercial compost, pasteurized (70 °C for 1 h) frass from BSFL reared on a FVBB diet, non-pasteurized frass from BSFL reared on a FVBB diet, pasteurized frass from BSFL reared on the GV diet, or non-pasteurized frass from BSFL reared on the GV diet. The results show that frass from BSFL reared on the GV diet, irrespective of pasteurization, inhibited FOL root colonization and reduced the severity of tomato Fusarium wilt to a far greater extent than frass from BSFL reared on a FVBB diet and commercial compost made of peat, seaweed, and shrimps. This study suggests that BSFL frass, depending on the larval rearing diet, has the potential to serve as a pasteurized or non-pasteurized soil amendment with prophylactic properties against FOL in tomato plants, opening new avenues of research for the valorization of BSFL frass.

Insect meals are promising alternative feed ingredients although their application is still not commonplace. Their inclusion requires the consideration of various factors to optimise growth, animal welfare, and feed costs. The insect meal form (whole or defatted) impacts the level of inclusion, in particular in feeds where low amount of lipids is needed (e.g. poultry). From a nutritional point of view, the factors that influence the insect meal characteristics include insect species, rearing substrates and production processes. Processing (drying, defatting) can dramatically influence the nutrient digestibility and availability that requires assessment through in vivo or in vitro trials, with differences being observed in relation to the entity of the defatting process as well. The inclusion of full-fat or defatted meal may impact the final product quality (fatty acid profile). Low digestibility of chitin is also a limiting factor. Studies to increase the digestibility of insect meals using additives are ongoing. For these reasons, when different insect protein suppliers are used for feed production, chemical analyses need to be performed. In addition to the nutritional aspect, in some species (i.e. fish), a physical evaluation of the feed is necessary. In particular, the high fat content of whole larvae meal may increase the mixture viscosity and decrease the pellet stability, resulting in nutrient loss. Palatability affects feed ingestion; though insect meals seem well accepted, some palatability issues have been reported at high inclusion levels. It is however not clear if these issues are due to the level of inclusion or to some intrinsic characteristics of the meal used. Finally, the crucial factor for the future practical incorporation of insect meals in animal feeds is the availability and consistency of the supply. Without large and consistent quantities, it will be difficult for feed producers to incorporate these alternative ingredients within their production processes.

There is a growing interest in the ability of black soldier fly ( Hermetia illucens ) larvae (BSFL) to convert low-value organic residues into high-value products. This leads to more publications with conversion data for various organic resources. However, these results are rarely comparable between laboratories due to differences in study protocols. This hinders comparisons among studies, the use of results in practice, and overall advancement in BSFL conversion research. Therefore, a standardised research protocol was developed for nursing, rearing and harvesting of BSFL for feed assessment. The utility of this protocol, was assessed via an international ring test with 9 partners. One batch of Gainesville diet (wheat bran (50%), alfa-alfa (30%) and maize (20%)) was produced and distributed among the partners to avoid dietary variations. Five-day-old BSFL larvae were used for the growth trial with six replicates per partner. Average larval weight was assessed after 3 days, 7 days, and harvest (>10% prepupae). Total yield and frass were recorded, and samples were chemically analysed to allow the quantification of the conversion efficiency. The results were used to calculate the within and between partner variability of the protocol. The results indicate that for the biological parameters (average weight, yield and density) the within partner variability was 24% and the between partner variability was 60%. For the assessed chemical parameters (N, fat, ash, P, K, pH), both the within and between variability was lower (respectively 9 and 28%). The results of this study give a first indication of the variability that can be expected within and between BSFL feeding experiments for different parameters and can therefore serve as guideline when developing a new experimental designs, assess standard operating procedures and other applications. The protocol can be used as first basis for future feed experiments, improving the comparability of results.

A range of issues related to sustainability in the agrifood industry have spurred interest in mass production of insects as human food and animal feed alternatives. This rapidly evolving sector addresses several challenges, including the management of food waste or agrifood by-products and the production of alternative animal proteins demonstrating low environmental impacts that improve sector circularity. The mass production of insects on agrifood processing wastes or by-products represents an opportunity to address these challenges. While the production of insects offers prospects for sustainable protein production, a major side stream is the production of frass or larval excrement including uneaten feed and chitin-rich exuviae (derived from multiple larval moults). The production of each tonne of edible insects generates 2 to 4 tonnes of frass with an interesting potential in agriculture versus traditional organic amendments (compost, manure, biochar). This review aims to demonstrate the characteristics of frass, its common harvest and conditioning methods, its optimal application rates for planting crops, the mechanisms by which it can protect plants against biotic and abiotic stresses and demystify the risks and potential associated with its application in agriculture. The characteristics of frass are compared with those of conventional fertilizers or other. This report also compiles the Canadian, US and European regulatory frameworks as a novel plant fertilizer and aims to pave the way for future research necessary for its valorization in plant production.

The larvae of the Black Soldier Fly ( Hermetia illucens ) provide numerous ecological benefits, leading to significant commercial advancements. These benefits include the bioconversion of low-value waste into high-value feed and soil amendments. Understanding how the bacterial and eukaryotic microbiota communities affect host performance becomes vital for the optimization and specialization of industrial-scale rearing. This study investigates H. illucens -associated microbiota taxonomic composition and dynamics across the developmental cycle (eggs, neonates, larvae, prepupae, and imago X0 to second generation X1) when reared on two substrates: (i) plant-based (Housefly Gainesville diet) and (ii) animal-based (poultry hatchery waste). By using the 16S gene amplicon metataxonomic approach, we found that the results revealed that bacterial microbiota inherited from parents reared on a different substrate may have induced dysbiosis in the progeny. Specifically, the interaction networks of individuals reared on hatchery waste showed a high prevalence of negative interactions and low connectivity. Proteobacteria (39–92%), Firmicutes (4–39%), Bacteroidota (1–38%), and Actinobacteria (1–33%). In animal feed-reared individuals, Firmicutes reached the highest relative abundance (10–80%), followed by Proteobacteria (6–55%), Actinobacteria (1–31%), and Bacteroidota (0–22%). The rearing substrate was the main driver of microbiota composition, while the developmental stage influenced only the whole individual's bacterial microbiota composition. Gut regions were associated with distinct bacterial composition and richness, with diversity decreasing along the digestive tract. For the first time, microeukaryotes of the microbiota other than Fungi were investigated using 18S genetic marker amplicon sequencing with novel blocking primers specific to the Black Soldier Fly. Microeukaryotes are a neglected part of multitrophic microbiota communities that can have similar effects on their hosts as bacterial microbiota. Microeukaryotes from seven orders were identified in black soldier flies, including potential pathogens (e.g., Aplicomplexa group). Nucletmycea were the dominant class throughout development, followed by Holozoa and Stramenophiles. The eukaryote microbiota was structured by developmental stages but not by gut regions. Insights from this study are a stepping stone toward the microbiological optimization of black soldier flies for industrial rearing, highlighting how a synthetic microbiota assembly should be tailored to the rearing environment of the larvae at a targeted developmental stage.

Black soldier fly larvae (BSF, Hermetia illucens) have gained much attention for their industrial use as biowaste recyclers and as a new source of animal proteins. The functional effect that microbiota has on insect health and growth performance remains largely unknown. This study clarifies the role of microbiota in BSF ontogeny by investigating the differential genomic expression of BSF larvae in axenic conditions (i.e., germfree) relative to non-axenic (conventional) conditions. We used RNA-seq to measure differentially expressed transcripts between axenic and conventional condition using DESeq2 at day 4, 12 and 20 post-hatching. Gene expression was significantly up or down-regulated for 2476 transcripts mapped in gene ontology functions, and axenic larvae exhibited higher rate of down-regulated functions. Up-regulated microbiota-dependant transcriptional gene modules included the immune system, the lipid metabolism, and the nervous system. Expression profile showed a shift in late larvae (day 12 and 20), exposing a significant temporal effect on gene expression. These results provide the first evidence of host functional genes regulated by microbiota in the BSF larva, further demonstrating the importance of host-microbiota interactions on host ontology and health. These results open the door to optimization of zootechnical properties in alternative animal protein production, biowaste revalorization and recycling.

Overwinter feed restriction followed by spring refeeding is proposed as a strategy to improve productivity and sustainability of Arctic charr production. A 257-day experiment was conducted with different feeding regimes to evaluate compensatory growth response in growth and physiological state of juvenile fish (150-200 g) reared under seasonal temperature and photoperiod. Five experimental groups in replicates were created based on frequency (C = continuous and P = periodic) and feed restriction level (0, 50 and 100%): C100%, P50%, C50%, P0% and C0%. After a period of acclimation of one month, two distinct phases of the growth trial were conceived: a restriction period (102 days) followed by a refeeding period (126 days). The growth (SGR's, organ indexes (HSI, CSI, ISI and VSI), FCE and FI) and pyloric caeca digestive (TRYP, CHY) and metabolic (LDH and CS) enzyme activity, stress levels (cortisol, HSP70 and hematocrit), morphometric traits (body mass, length and K) and muscle proximate composition were evaluated at different intervals. Our results indicate that 1) a limited period of food restriction (P0%) or a prolonged starving (C0%) enabled the observation of a complete growth compensation after 86 and 126 days post-refeeding respectively with improved feed conversion efficiency (FCE of 1.20 for P0% and C0% compared to 1.06 for the control); 2) Arctic charr under a fair level of food reduction applied either periodically (P50%) or continuously (C50%) can achieve similar growth than un-restricted fish; 3) during the refeeding period, lower variability in growth was successfully induced (C100% > P50% > C50% > P0% > C0%); 4) rapid size or mass adjustment of key digestive organs such as pyloric caeca and intestine is associated with feed restriction and refeeding (reduction and increase in relative size respectively); 5) enzymatic activities of TRY, LDH and CS measured at the last sampling of the restriction phase indicate some level of adjustments that quickly receded to levels similar to the control group (9 days post-refeeding); 6) lipid content value was significantly higher in fish from the C100% group in comparison to C50%, P0% and C0% groups at the end of the restriction phase, indicating that lipid depletion is a prerequisite to compensatory growth induction and 7) in comparison to the control un-restricted fish, the stress levels, as estimated by stress markers (cortisol, HSP70 or hematocrit) were not affected by the level of feed restriction. Feed restriction has been successfully used to promote compensatory and catch-up growth. Here we suggest that studies are however required to further explore to which extent feed-restriction could induce vulnerability of Arctic charr, during sub-optimal growth conditions. Finally, defining the best sequence of feed restriction and refeeding should ensure imple-mentation of production and benefit while maintaining optimal health conditions.

With the growth of the insect farming industry, increasing quantities of insect manure (called frass) must be upcycled. This research provides one of the first sources of information regarding the potential plant growth enhancement of Tenebrio molitor's frass on garden plants. It aims at demonstrating that frass is a promising fertilizer for plant production. Nine vegetables, one herb, and three flowers were planted on the roof of "La Centrale Agricole" in Montreal. Plants were grown in a 5% compost-enriched substrate (v/v) (control) and fertilized with 0.5% (v/v) frass (treatment 2) or an isonitrogen concentration of hen manure (treatment 3). Plant growth (germination, height, N flowers) and productivity (biomass) were assessed regularly throughout the growing season. Although beets and carrots' seedling emergence was inhibited by both manures, this did not lead to reduced edible biomass compared to the control (germination was unaffected for corn, radish, and arugula). Similar to hen manure, frass resulted in a 16-fold increase of the edible biomass as compared to the control. Frass-fertilized plants had larger and more numerous flowers than control plants. Our results confirm that insect manure should be recognized as a suitable fertilizer for multiple crops, and should be regulated like other manures.

https://doi.org/10.1093/af/vfad047 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. Copyright © 2023 American Society of Animal Science Feature Article The edible insect sector in Canada and the United States

Frass, the residual material resulting from the bioconversion of organic matter by black soldier fly larvae (BSFL), has gained attention as a sustainable alternative to conventional fertilizers due to its high nutrient content. Additionally, frass has been found to possess antifungal properties, which can help control plant pathogens affecting horticultural crops. In this study, frass from BSFL reared on the Gainesville diet, a universally employed reference/control diet, was investigated in vitro for its effect on the growth of seven important fungal/oomycete pathogens. Dual culture overlay assays clearly showed that fresh Gainesville diet extract, as well as BSFL frass extract derived from this diet, contained microorganisms producing compound(s) that strongly inhibit(s) the mycelial growth of fungal/oomycete plant pathogens. Fungi and bacteria were then isolated from the fresh Gainesville diet and BSFL frass using the serial dilution technique. Among the different fungi/bacteria isolated, the isolate GV1-11 in Gainesville diet and FGV15-6 in frass demonstrated strong antifungal/anti-oomycete activity. Both isolates were genetically identified by whole-genome sequencing as Bacillus velezensis, a bacterium used as a biocontrol agent, strongly suggesting that B. velezensis, which is present in the Gainesville diet, can survive the process of BSFL rearing and is one of the key factors contributing to the observed antifungal and anti-oomycete activity in the resulting frass. This work underlines the importance of the inherent microbial characteristics of feedstocks on the antifungal/anti-oomycete activity of frass and points out the possibility of exploiting frass to control plant pathogens affecting horticultural crops.

Increasing concerns related to the negative environmental impacts of food waste havemotivated the development of new solutions to complete the waste cycle of organic residues. One particular "waste" product, the solid digestate from anaerobic digestion, has been identified for further bioprocessing. Black soldier fly (BSF, Hermetia illucens) larvae are known for their great potential in the processing of organic waste. In this study, this potential was investigated to further process the digestate waste stream. Digestate is considered a low potential source of nutrients for larvae due to the presence of different fiber fractions. However, the lignocellulosic matter in this residue could be enzymatically hydrolyzed to release residual carbohydrates. For this study, digestate from a full-scale anaerobic digestion plant in Quebec (Canada) which processes a range of feedstocks (fruits, vegetables, garden wastes, sludge derived from dairy processing and wastewater treatment) was sourced. Digestate was treated with Accelerase® DUET enzyme complex to hydrolyze lignocellulosic matter and compared to a standard diet. For each treatment, 600 four-day old larvae were fed daily with 160 g (70% relative humidity) of diets for 6 days and harvested 3 days later. Although their growth and total biomass were significantly lower than the standard diet, larvae fed on hydrolyzed digestate were almost two times larger than the larvae fed on crude digestate. Furthermore, the content of organic matter, lipids and minerals in the diets and frass were analyzed. Finally, the feasibility of applying BSF treatment for digestate valorization is discussed. According to this study, enzyme-treated digestate does not allow efficient larval growth compared to the standard diet. The development of a more effective method of pretreatment is required for BSF larvae to become an eco-friendly solution for digestate valorization.