Replacement of Fish Meal by Defatted Yellow Mealworm (Tenebrio molitor) Larvae in Diet Improves Growth Performance and Disease Resistance in Red Seabream (Pargus major)

Effects of four types of natural bait on water quality, feeding, growth, and antioxidant enzyme activity of Monopterus albus in a recirculating aquaculture system

Monopterus albus is one of China's renowned and superior aquaculture species, with its seedlings mainly sourced from wild capture. One of the bottlenecks in M. albus aquaculture is the high mortality rate and low feeding initiation rate from stocking wild fry to the initiation of feeding. In production, trash fish is commonly used to wean M. albus juveniles onto feeding. In this study, we introduced three other natural feeds, earthworms (EW), yellow mealworms (YMW), and fly maggots (FM), with frozen trash fish (TF) serving as the control group, to evaluate the effects of these four natural feeds on the survival rate, feeding initiation, antioxidant enzymes activity, and body composition of M. albus juveniles under recirculating water aquaculture conditions. The experiment comprised four treatments, each with three replicates. Each replicate consisted of stocking 150 M. albus juveniles weighing 10.02 ± 0.89 g in size, raised for 5 weeks. The survival rate of the YMW group was 73.33%-85.33%, which was significantly higher than that of the other three bait groups (p < 0.05). The four bait groups showed no significant differences in final body weight and specific growth rate (SGR) (p > 0.05). The EW group showed the highest final body weight, with an average SGR of 2.73, whereas the YMW group had an average SGR of 1.87. The average daily feeding amount was significantly higher in EW and YMW groups than in the other two groups (p < 0.05). The percentage of feeding amount to fish weight in the EW group reached 7.3% in the fifth week. After 5 weeks of cultivation, NO2 --N content was significantly higher in the waters of the TF and EW groups than in the waters of the FM and YMW groups (p < 0.05), there was no significant difference in TAN content among the treatment groups (p > 0.05). Liver malondialdehyde content was significantly higher in the TF group than in the other bait groups (p < 0.05). GSH-Px activity was significantly higher in the EW group than in the FM group and YMW group. No significant differences in SOD and CAT activity and T-AOC were observed among the bait groups (p > 0.05). The increase in crude protein content was significantly higher in the TF group than in the FM group, but the increase in crude ash content was significantly lower in the TFgroup. In conclusion, Tenebrio molitor could potentially serve as one of the alternative feeds during the initial stages of M. albus juveniles stocking.

Dietary Black Soldier Fly (Hermetia illucens)-Dipterose-BSF-Enhanced Zebrafish Innate Immunity Gene Expression and Resistance to Edwardsiella tarda Infection

Dietary management using immunostimulants to protect fish health and prevent bacterial infection is widely practiced. Many insect species possess various bioactive substances that can improve animal health. We previously identified several bioactive polysaccharides derived from insects, including dipterose-BSF from black soldier fly (Hermetia illucens) larvae; this can stimulate innate immunity in mammalian macrophage RAW264.7 cells. However, the effect of dietary dipterose-BSF on the immune system of teleosts remains unclear. Here, we analyzed the immune status of zebrafish (Danio rerio) after 14 days of dietary inclusion of dipterose-BSF (0.01, 0.1, and 1 µg/g), followed by an immersion challenge using Edwardsiella tarda. To identify changes in the transcriptional profile induced by dipterose-BSF, we performed RNA-sequencing analyses of the liver and intestine. Differentially expressed genes were investigated, with both organs showing several upregulated genes, dominated by nuclear factor and tumor necrosis factor family genes. Gene Ontology analysis revealed several terms were significantly higher in the experimental group compared with the control group. Challenge tests suggested that dietary dipterose-BSF had some positive effects on disease resistance in fish, but these effects were not pronounced.

Dietary Replacement Effect of Fish Meal by Tuna By-Product Meal on Growth and Feed Availability of Red Sea Bream (Pagrus major)

The effect of substituting fish meal (FM) by tuna by-product meal (TBM) on growth and feed availability of red sea bream (Pagrus major) was investigated. Six experimental diets were crested to be isonitrogenous (51.5%) and isolipidic (14.5%). The control (Con) diet contained 55% FM. FM substitution in the Con diet was made in increments of 20 percentage points (20, 40, 60, 80, and 100%), named as the TBM20, TBM40, TBM60, TBM80, and TBM100 diets, respectively. Juvenile red sea bream were stocked into 18, 300 L flow-through tanks (50 fish/tank). Red sea bream were hand-fed with each diet until satiation for 8 weeks. No statistical differences in weight gain, specific growth rate (SGR), and feed consumption were found among red sea bream fed the Con, TBM20, and TBM40 diets. Furthermore, feed utilization of fish fed the TBM20, TBM40, TBM60, and TBM80 diets was comparable to red sea bream fed the Con diet. The biological indices, biochemical composition, and hematological parameters of fish were not statistically altered by dietary FM replacement with TBM. The greatest economic profit index was achieved in the TBM40 diet. In conclusion, the replacement of 40% FM with TBM in red sea bream diet appears to be the most recommendable approach without producing retarded growth and feed availability, but maximizing EPI to farmers.

Microplastics contamination in fish feeds: Characterization and potential exposure risk assessment for cultivated fish of Bangladesh

Fish feed is becoming an increasingly vital source of nourishment for farmed fish, which are mainly coming from marine fish and agricultural sources. Anthropogenic particles, such as microplastics, are abundant in both marine fish and agricultural byproducts that are utilized to make fish feed. This study investigated whether fish feed could be a source of microplastic contamination, and revealed that a 20 weeks adult farmed tilapia fish might consume up to 268.45 ± 1.438 microplastic particles via fish feed where finisher type feeds were found to be mostly contributory in this number. The microplastics were initially observed with a stereomicroscope and FESEM-EDS. Polymeric composition of microplastics was determined to be polypropylene (PP), nylon-6 (NY-6), polyethylene terephthalate (PET), polystyrene (PS), polyvinyl alcohol (PVA), polyethylene (PE), high- and low-density polyethylene (HDPE, LDPE), ethylene vinyl acetate (EVA), polycarbonate (PC), poly vinyl acetate (PVAc), poly urethane (PU) and polyvinyl chloride (PVC) by FTIR. Results also revealed that the size of microplastic particles in all fish feed ranged from 14 μm to 4480 μm, with 550 ± 45.45 to 11,600 ± 56.1 microplastic particles/kg of fish feed. The FESEM-EDS data demonstrated to overlook the microplastic surface along with attachment of heavy metals onto that surface such as Pb, Ni, and Co in finisher type feed that could create additional health risks.

Breeding Substrate Containing Distillation Residues of Mediterranean Medicinal Aromatic Plants Modulates the Effects of Tenebrio molitor as Fishmeal Substitute on Blood Signal Transduction and WBC Activation of Gilthead Seabream (Sparus aurata)

This work assesses the dietary use of two insect meals of Tenebrio molitor (TM) larvae reared in conventional (TM-10) or MAP-enriched substrates (MAP-TM-10) as fish meal replacements (10%) in the diets of gilthead seabream (Sparus aurata). Fish (n = 4500; 207.19 ± 1.47 g) were divided into three groups with triplicates: control (fed conventional diet), TM-10, and MAP-TM-10 groups. The fish were reared in floating cages for 12 weeks and the dietary effects on white blood cell activation, heat shock proteins, MAPKs, and apoptosis of the fish were evaluated. The MAP-TM-10 group exhibited the highest eosinophilic induction. Phosphorylated levels of p38 MAPK, p44/42 MAPK, HSP70, and HSP90 increased in the TM-10 and MAP-TM-10 groups. In terms of apoptosis, Bax levels were lower in the TM groups compared to the control, and the MAP-TM-10 group showed even lower levels than the TM-10 group. Bcl-2 levels increased in the TM-10 group compared to the control, and further increased in the MAP-TM-10 group. The Bax/Bcl-2 ratio, an apoptosis indicator, decreased in the TM groups, with the MAP-TM-10 group showing a further decrease compared to TM-10. These findings suggest that insects' breeding substrate being enriched with MAPs modulated the effect of TM on cellular stress and apoptosis.

Sustainable Fish Feeds with Insects and Probiotics Positively Affect Freshwater and Marine Fish Gut Microbiota

Aquaculture is the fastest-growing agricultural industry in the world. Fishmeal is an essential component of commercial fish diets, but its long-term sustainability is a concern. Therefore, it is important to find alternatives to fishmeal that have a similar nutritional value and, at the same time, are affordable and readily available. The search for high-quality alternatives to fishmeal and fish oil has interested researchers worldwide. Over the past 20 years, different insect meals have been studied as a potential alternate source of fishmeal in aquafeeds. On the other hand, probiotics-live microbial strains-are being used as dietary supplements and showing beneficial effects on fish growth and health status. Fish gut microbiota plays a significant role in nutrition metabolism, which affects a number of other physiological functions, including fish growth and development, immune regulation, and pathogen resistance. One of the key reasons for studying fish gut microbiota is the possibility to modify microbial communities that inhabit the intestine to benefit host growth and health. The development of DNA sequencing technologies and advanced bioinformatics tools has made metagenomic analysis a feasible method for researching gut microbes. In this review, we analyze and summarize the current knowledge provided by studies of our research group on using insect meal and probiotic supplements in aquafeed formulations and their effects on different fish gut microbiota. We also highlight future research directions to make insect meals a key source of proteins for sustainable aquaculture and explore the challenges associated with the use of probiotics. Insect meals and probiotics will undoubtedly have a positive effect on the long-term sustainability and profitability of aquaculture.

Effects of Yellow Mealworm (Tenebrio molitor) on Growth Performance, Hepatic Health and Digestibility in Juvenile Largemouth Bass (Micropterus salmoides)

This study investigated the effects of yellow mealworm meal (TM) on growth performance, hepatic health and digestibility in juvenile largemouth bass (Micropterus salmoides). The fish were fed with the basic feed and the test feed (70% basic feed and 30% raw materials) containing Cr₂O₃, and feces were collected for digestibility determination. The fish were fed with five isonitrogenous (47% crude protein) and isolipidic (13% crude lipid) diets, in which fishmeal (FM) was replaced with 0% (TM0), 12% (TM12), 24% (TM24), 36% (TM36) and 48% (TM48) TM. The fish were reared in cylindrical plastic tanks in a recirculating aquaculture system for 11 weeks. The apparent digestibility coefficients (ADC), of dry matter, crude protein and crude lipid, in largemouth bass of TM were 74.66%, 91.03% and 90.91%, respectively. The ADC of total amino acid (TAA) of TM in largemouth bass was 92.89%, and the ADC of essential amino acid (EAA) in TM in largemouth bass was 93.86%. The final body weight (FBW), weight gain rate (WGR) and specific growth rate (SGR) in the TM24 group were significantly higher than those in other groups. Similarly, the highest mRNA expression levels of hepatic protein metabolism genes (pi3k, mtor, 4ebp2 and got) and antioxidant enzyme (glutathione peroxidase, Gpx; catalase, Cat) activities were observed in the TM24 group. Moreover, the expression levels of anti-inflammatory factors (il-10 and tgf) in liver were up-regulated and the expression levels of pro-inflammatory factors (il-8 and il-1β) in liver were down-regulated. Quadratic regression model analysis, based on weight gain rate (WGR) against dietary TM level, indicated that the optimum level of dietary TM replacing FM in largemouth bass diet was 19.52%. Appropriate replacement levels (less than 36%) of FM by TM in the diets can enhance the antioxidant capacity and immunity of largemouth bass. However, high levels of FM substitution with TM (more than 48%) in the feeds can damage the liver health and inhibit the growth of largemouth bass. Notably, largemouth bass has high ADC and high utilization of TM, which indicates that it is feasible to use TM as feed protein source for largemouth bass.

Insect biorefinery: A circular economy concept for biowaste conversion to value-added products

With rapid growing world population and increasing demand for natural resources, the production of sufficient food, feed for protein and fat sources and sustainable energy presents a food insecurity challenge globally. Insect biorefinery is a concept of using insect as a tool to convert biomass waste into energy and other beneficial products with concomitant remediation of the organic components. The exploitation of insects and its bioproducts have becoming more popular in recent years. This review article presents a summary of the current trend of insect-based industry and the potential organic wastes for insect bioconversion and biorefinery. Numerous biotechnological products obtained from insect biorefinery such as biofertilizer, animal feeds, edible foods, biopolymer, bioenzymes and biodiesel are discussed in the subsequent sections. Insect biorefinery serves as a promising sustainable approach for waste management while producing valuable bioproducts feasible to achieve circular bioeconomy.

Defatted black soldier fly (Hermetia illucens) in pikeperch (Sander lucioperca) diets: Effects on growth performance, nutrient digestibility, fillet quality, economic and environmental sustainability

The use of insect meal in aquafeed formulations has recently gained attention. Detailed knowledge about the inclusion levels for pikeperch (Sander lucioperca), a promising candidate for intensive aquaculture in Europe remains, however, fragmented. In the present study, 4 isoproteic (45% dry matter) and isoenergetic (21 MJ/kg) diets were formulated, including a control diet (H0) containing 30% fishmeal (FM) on an as-fed basis and the other 3 diets in which FM protein was replaced by defatted black soldier fly (Hemetia illucens) meal (HIM) at 25%, 50%, and 100% (diet abbreviation H9, H18 and H36, corresponding to an inclusion level of 9%, 18% and 36%, respectively). The feeding trial was performed in triplicate groups of 50 juvenile pikeperch (mean weight, 68.7 g) fed with experimental diets for 84 d during which the growth performance, nutrient digestibility, fillet quality and economic and environmental sustainability of rearing pikeperch were evaluated. Our findings indicated that pikeperch in H0, H9, and H18 groups displayed better results regarding growth performance indices, except for survival rate where no significant difference among groups was recorded (P = 0.642). A significantly lower organ-somatic index, including hepatosomatic, viscerosomatic and perivisceral fat index, was found in fish in H18 groups than other groups (P < 0.05). Inclusion of HIM affected the digestibility of the nutrients and resulted in an almost linear reduction in the apparent digestibility coefficient of dry matter and protein. Concerning the fillet quality, dietary HIM negatively affected the protein and ash contents of the fish fillets, while the crude fat remained unchanged. Dietary HIM did not significantly modify total saturated, monounsaturated and polyunsaturated fatty acids in the fillets of fed pikeperch (P > 0.05) but did reduce total n-3 fatty acids (P = 0.001) and increased total n-6 (P < 0.001). Increasing inclusion levels of HIM reduced the environmental impacts associated with fish in-to-fish out ratio but entailed heavy burdens on energy use and eutrophication. Low and moderate inclusion levels of HIM did not negatively affect land use and water use compared to an HIM-free diet (P > 0.05). The addition of HIM at a level as low as 9% elicited a similar carbon footprint to that of the control diet. The economic conversion ratio and economic profit index were negatively affected at increased insect meal inclusion levels. This study has shown that the incorporation of HIM in feed formulations for pikeperch is feasible at inclusion levels of 18% without adverse effects on growth performance parameters. The feasibility also highlighted the environmental benefits associated with land use and marine resources required to produce farmed fish.

Effects of Replacing Fishmeal with Defatted Black Soldier Fly (Hermetia illucens Linnaeus) Larvae Meal in Japanese Eel (Anguilla japonica) Diet on Growth Performance, Fillet Texture, Serum Biochemical Parameters, and Intestinal Histomorphology

An 8-week feeding trial was conducted to investigate the effects of replacing fishmeal with defatted black soldier fly larvae meal (DBSFLM) in the diets of Japanese eel on their growth performance, fillet texture, serum biochemical parameters, and intestinal histomorphology. Six isoproteic (520 g kg^-1), isolipidic (80 g kg^-1), and isoenergetic (15 MJ kg^-1) diets were formulated with fishmeal replacement levels of 0% (R0), 15% (R15), 30% (R30), 45% (R45), 60% (R60), and 75% (R75). The growth performance, feed utilization efficiency, survival rate, serum liver function enzymes, antioxidant ability, and lysozyme activity of fish were not affected (P > 0.05) by DBSFLM. However, the crude protein and cohesiveness of the fillet in groups R60 and R75 significantly decreased, and the fillet hardness significantly increased (P < 0.05). Additionally, the intestinal villus length significantly decreased in the R75 group, and the goblet cell densities were significantly lower in the R45, R60, and R75 groups (P < 0.05). Overall, high levels of DBSFLM did not affect growth performance and serum biochemical parameters but significantly altered fillet proximate composition and texture and intestinal histomorphology (P < 0.05). The optimal fishmeal replacement level is 30% with 184 g kg^-1 DBSFLM.

Effects of the Replacement of Dietary Fish Meal with Defatted Yellow Mealworm (Tenebrio molitor) on Juvenile Large Yellow Croakers (Larimichthys crocea) Growth and Gut Health

Simple Summary

Fish meal is the most common protein source in aquatic feeds. The decline of fishery resources and the increased demand have led to a shortage of fish meal resources in recent years. To ensure the sustainable development of the aquaculture industry, it is crucial to find a low-price, high-quality protein source to replace fish meal. In this study, substituting fish meal of large yellow croakers (Larimichthys crocea) diets with defatted yellow mealworm (Tenebrio molitor) test was carried out. The results showed that the dietary fish meal could be replaced by 15% defatted yellow mealworm in feeds containing 40% fish meal without adversely affecting the growth of large yellow croakers, and to some extent improving the immunity of the organism. Substitution levels of 15% or more are beneficial for digestive enzymes. In addition, the moderate addition of defatted yellow mealworm improves intestinal health by improving the structure and microbial composition of the gut.

Abstract

This study was conducted to investigate the effects of Tenebrio molitor meal (TM) replacement for fish meal (FM) on growth performance, humoral immunity, and intestinal health of juvenile large yellow croakers (Larimichthys crocea). Four experimental diets were formulated by replacing FM with TM at different levels—0% (TM0), 15% (TM15), 30% (TM30), and 45% (TM45). Triplicate groups of juveniles (initial weight = 11.80 ± 0.02 g) were fed the test diets to apparent satiation two times daily for eight weeks. There was no significant difference in final body weight (FBW) and weight gain rate (WG) among TM0, TM15, and TM30, while TM45 feeding significantly reduced the FBW and WG. Compared with TM0, AKP activity in serum was significantly decreased in TM45, while the TM15 group remarkably increased LZM activity. TM30 showed significantly higher serum C3 levels compared to the TM0 group, while the TM addition groups decreased the C4 levels significantly in the serum. In terms of intestinal histology, the addition of TM increased the height and thickness of the intestinal villus and also increased the thickness of the intestinal muscles significantly. The addition of TM significantly reduced the serum DAO and D-lactate concentrations. The results of 16S rRNA gene sequencing showed that the addition of TM significantly enhanced the relative abundance of Bacilli and Lactobacillus and contributed to the decrease in the relative abundance of Plesiomonas. In addition, the TM30 and TM45 groups significantly reduced the abundance of Peptostreptococcaceae. Overall, our results indicated that TM could be a viable alternative protein source, 6.7% TM supplantation (replacing 15% FM) in large yellow croaker feed improved humoral immunity and intestinal health with no adverse effects on growth. Furthermore, the replacement of FM with 30% and 45% TM adversely affects growth and humoral immunity.

Recent advances in the utilization of insects as an ingredient in aquafeeds: A review

The aquafeed industry continues to expand in response to the rapidly growing aquaculture sector. However, the identification of alternative protein sources in aquatic animal diets to replace conventional sources due to cost and sustainability issues remains a major challenge. Recently, insects have shown tremendous results as potential replacers of fishmeal in aquafeed. The present study aimed to review the utilization of insects in aquafeeds and their effects on aquatic animals' growth and feed utilization, immune response and disease resistance, and fish flesh quality and safety. While many insect species have been investigated in aquaculture, the black soldier fly (Hermetia illucens), and the mealworm (Tenebrio molitor) are the most studied and most promising insects to replace fishmeal in aquafeed. Generally, insect rearing conditions and biomass processing methods may affect the product's nutritional composition, digestibility, shelf life and required insect inclusion level by aquatic animals. Also, insect-recommended inclusion levels for aquatic animals vary depending on the insect species used, biomass processing method, and test organism. Overall, while an appropriate inclusion level of insects in aquafeed provides several nutritional and health benefits to aquatic animals, more studies are needed to establish optimum requirements levels for different aquaculture species at different stages of development and under different culture systems.

Potential of mealworms used in polyhydroxyalkanoate/bioplastic recovery as red hybrid tilapia (Oreochromis sp.) feed ingredient

Polyhydroxyalkanoates (PHAs) are bio-based polymers produced in bacterial cells to replace some petrochemical plastics. It has always been a challenge to commercialise PHA due in part to the costly recovery processes of the PHA granules from the bacterial cells. The biological approach of using mealworms, Tenebrio molitor, for the recovery of PHA from the bacterial cells is a newly established method that is at the scale-up stage. On the other hand, the aquaculture feed industry needs a low-cost mealworm meal as a protein source. We aimed at studying the nutritional value of the mealworms (which are by-products) used for the poly(3-hydroxybutyrate) (PHB) (the most common type of PHA) recovery from the bacterial and examining the effect of the mealworms on the growth performance, and feed utilization efficiency of red hybrid tilapia (Oreochromis sp.). The cells were fed to the mealworms to digest the proteinaceous cellular materials and excrete the PHB granules in the form of fecal pellets. The resulting mealworms were used as fishmeal replacement to formulate five isonitrogenous (35% crude protein) and isolipidic (8% lipid) diets at mealworm meal (MwM) inclusion levels of 0% (MwM0/control diet), 25% (MwM25), 50% (MwM50), 75% (MwM75) or 100% (MwM100). The results showed good nutritive value mealworms [high protein (75%), low-lipid (10%)] and up to 75% MwM inclusion diet was good in supplying satisfactory nutrients and energy to the red hybrid tilapia. This approach is beneficial in a way that minimal cost was involved in recovering kilograms of PHB and the proteins, lipids, and minerals from the bacterial cells do not end up as wastes but in turn, are used as nutrition by the larvae.

The Effects of Silkworm-Derived Polysaccharide (Silkrose) on Ectoparasitic Infestations in Yellowtail (Seriola quinqueradiata) and White Trevally (Pseudocaranx dentex)

The effect of silkworm-derived polysaccharide silkrose on fish ectoparasites was investigated. When juvenile yellowtail (Seriola quinqueradiata) fed diets containing silkrose were artificially infected with Benedenia seriolae, a fish ectoparasite, the numbers of parasitized B. seriolae were significantly lower compared to that in fish in the control group without silkrose treatment. Furthermore, when juvenile yellowtails were severely infected with B. seriolae, no mortality was observed in the silkrose-treated group, compared to more than 60% in the control group. In field studies carried out at a fish farm with yellowtail and white trevally (Pseudocaranx dentex), oral treatment with silkrose significantly reduced B. seriolae parasitism in yellowtail and Caligus longipedis and Neobenedenia girellae parasitism in white trevally. Silkrose treatment also reduced blood levels of cortisol, a stress hormone in both species. The changes in gene expression in the epidermis of yellowtail by silkrose treatment were also investigated, showing that the expression of various genes, including factors involved in immunity, stress response, and wound healing, was changed by the treatment. These findings indicate that silkworm-derived silkrose effectively prevents infection by external parasites in yellowtail and white trevally.

Effect of Feed Containing Hermetia illucens Larvae Immunized by Lactobacillus plantarum Injection on the Growth and Immunity of Rainbow Trout (Oncorhynchus mykiss)

Simple Summary

In this study, we evaluated the effect on the growth and immunity of rainbow trout of a feed formulated using Hermetia illucens with increased antimicrobial peptides expression by Lactobacillus plantarum infection (ImHIL). As a result, growth and immunological indicators improved, and therefore, ImHIL is expected to become a good feed source for rainbow trout aquaculture.

Abstract

We investigated the effects of a feed containing Hermetia illucens larvae injected with bacteria on the growth and immunity of Oncorhynchus mykiss. The feed was prepared by replacing fishmeal in feed with 25 and 50% nonimmunized (HIL25, HIL50) or immunized HIL (ImHIL25, ImHIL50), and its protein:fat:carbohydrate ratio was 45:15:18. ImHIL extracts showed inhibitory activity against fish pathogenic bacteria. Both red blood cell count and insulin-like growth factor-1 as the growth indicator were the highest among the groups at week 6 after feeding in the ImHIL50 group. As immune indicators, blood aspartate aminotransferase levels were lower in the ImHIL25 and ImHIL50 groups than in that of other groups at week 6 after feeding, and lysozyme content was significantly higher in ImHIL25 and ImHIL50. The above results demonstrate that ImHIL has a beneficial effect on the improvement of growth and immunity. Accordingly, we suggest that ImHIL has the potential to be a good feed source in aquaculture.

Growth of Yellowtail (Seriola quinqueradiata) Fed on a Diet Including Partially or Completely Defatted Black Soldier Fly (Hermetia illucens) Larvae Meal

Simple Summary

Insects which can be reared artificially, such as the black soldier fly, housefly or yellow mealworm are considered as promising feed sources for sustainable aquaculture. The present study is the first to reveal the potential of diets containing insect meal for juvenile yellowtail. The growth of fish fed diets in which fish meal was replaced by 10–30% partially defatted black soldier fly larvae meal was decreased in accordance with the content of the larvae meal. On the other hand, growth of fish with a diet including 20% completely defatted larvae meal was equivalent to that with a diet of the partially defatted larvae meal. Thus, the fat fraction of black solider fly larvae could cause growth retardation of yellowtail, and the defatting process of the insect meal may be important in the manufacture of black soldier fly larvae meal for yellowtail.

Abstract

Against a background of increased demand for fish meal (FM), black soldier fly larva is a promising alternative feed source for sustainable aquaculture. Yellowtail, the most popular farmed fish in Japan, is a carnivorous fish; therefore, it requires a high proportion of FM in its diet. This study represents the first example of yellowtail fed on a diet including insect meal as a replacement for FM. Partially defatted black soldier fly meal (PDBM) comprised 49.0% crude protein and 23.2% crude fat, while completely defatted black soldier fly meal (CDBM) contained less than 10% crude fat, as the same level as FM was achieved with defatting PDBM using hexane. In feeding trials, growth of the fish was reduced in accordance with PDBM content: 10%, 20%, and 30% in their diet. Although a diet including 8% CDBM (with the same protein composition as 10% PDBM) also resulted in decreased fish growth, growth with a diet including 16% CDBM (with the same protein composition as 20% PDBM) was significantly higher than that of 20% PDBM, and equivalent to that of 10% PDBM. Therefore, even 10% of partially or completely black soldier fly larvae meal in diets inhibited growth in juvenile yellowtail, and we found that removal of the fat fraction could improve fish growth.

Effects of dietary silkrose of Antheraea yamamai on gene expression profiling and disease resistance to Edwardsiella tarda in Japanese medaka (Oryzias latipes)

We previously identified a novel acidic polysaccharide, silkrose-AY, from the Japanese oak silkmoth (Antheraea yamamai), which can activate an innate immune response in mouse macrophage cells. However, innate immune responses stimulated by silkrose-AY in teleosts remain unclear. Here, we show the influence of dietary silkrose-AY in medaka (Oryzias latipes), a teleost model, in response to Edwardsiella tarda infection. Dietary silkrose-AY significantly improved the survival of fish and decreased the number of bacteria in their kidneys after the fish were artificially infected with E. tarda by immersion. We also performed a microarray analysis of the intestine, which serves as a primary barrier against microbial infection, to understand the profiles of differentially expressed genes (DEGs) evoked by silkrose-AY. The dietary silkrose-AY group showed differential expression of 2930 genes when compared with the control group prior to E. tarda infection. Gene ontology and pathway analysis of the DEGs highlighted several putative genes involved in pathogen attachment/recognition, the complement and coagulation cascade, antimicrobial peptides/enzymes, opsonization/phagocytosis, and epithelial junctional modification. Our findings thus provide fundamental information to help understand the molecular mechanism of bacterial protection offered by insect-derived immunostimulatory polysaccharides in teleosts.

Effect of a Black Soldier Fly Ingredient on the Growth Performance and Disease Resistance of Juvenile Pacific White Shrimp (Litopenaeus vannamei)

Simple Summary

This study investigates the use of a Black soldier fly (Hermetia illucens) ingredient in juvenile shrimp (Litopenaeus vannamei) diets at various inclusion rates (4.5, 7.5, and 10.5%), monitoring both the growth performance and then health performance in the face of three separate challenges (White spot syndrome virus, Vibrio parahaemolyticus, and osmotic stress). This work showed that growth performance (measured through weight gain, feed conversion ratio, and specific growth rate) of L. vannamei was significantly improved in a linear trend with the inclusion of the Black soldier fly ingredient (p < 0.05), whilst health performance was not significantly altered. Overall, the Black soldier fly ingredient proves to be a promising additive for L. vannamei diets, impacting performance and sustainability positively.

Abstract

This study was performed as part of developing a functional feed ingredient for juvenile Pacific white shrimp (Litopenaeus vannamei). Here we assess the effects of dietary inclusion of a Black Soldier Fly Ingredient (BSFI) from defatted black soldier fly (Hermetia illucens) larvae meal on growth performance, tolerance to salinity stress, and disease resistance when challenged with Vibrio parahaemolyticus or a strain of white spot syndrome virus (WSSV). A control diet was used for comparison with three test diets including 4.5, 7.5, and 10.5% of BSFI (BSFI4.5, BSFI7.5, and BSFI10.5). After 28 days, all diets with BSFI had improved weight gain, feed conversion ratio (FCR) and specific growth rate (SGR) compared to control. Indeed, SGR was significantly improved from inclusion of 4.5% in the diet, whilst FCR was significantly improved at 7.5% (p < 0.05). During the growth trial, survival was not affected by diet. Shrimp health performance was not significantly affected by the diets across the disease and salinity challenges. Overall, the results indicate that the inclusion of BSFI from H. illucens improves the performance of juvenile L. vannamei.

The Use of Defatted Tenebrio molitor Larvae Meal as a Main Protein Source Is Supported in European Sea Bass (Dicentrarchus labrax) by Data on Growth Performance, Lipid Metabolism, and Flesh Quality

Objective

This study aims to determine the maximal inclusion level of defatted (d-) Tenebrio molitor larvae meal (TM) able to replace dietary fishmeal (FM) without compromising growth performance, general metabolism, and flesh quality traits in European sea bass, and to evaluate the major underlying physiological mechanisms.

Materials and Methods

Fish (55 ± 2 g) were fed with diets containing increasing levels of dTM: 0, 40, 80 and 100% (CTRL, TM40, TM80, and TM100, respectively) to replace FM. After 10 weeks of feeding, the growth performance, nutrient and energy balance, intestinal integrity, plasma metabolites and the expression of genes related to growth and nutrient metabolism, in liver and muscle were determined. The fatty acids (FA) profile, textural properties and color were also evaluated in muscle.

Results

Protein and lipids digestibility remained unaltered up to 80% dTM inclusion. Growth performance parameters were similar among dietary treatments. The dTM inclusion increased the hepatosomatic index in fish fed TM100. Muscle eicosapentaenoic acid, docosahexaenoic acid and n-3 long-chain polyunsaturated FA levels were maintained up to 80% dTM inclusion, but total cholesterol and non-esterified FA increased with dietary dTM inclusion. In liver, the expression of elongation of very long-chain FA protein 6 (elovl6) and FA desaturase 2 (fads2) did not change in fish fed TM40 and TM80, but elovl6 decreased whilst fads2 increased in fish fed TM100 when compared to those fed CTRL. The expression of cholesterol 7 alpha-monooxygenase (cyp7a1) decreased with dietary dTM inclusion. In muscle, the expression of myoblast determination protein-2 (myod2) decreased in fish fed TM80 and TM100.

Conclusion

It is feasible to substitute dietary FM by dTM up to 80% in European sea bass without detrimental effects on nutrient digestibility, growth performance and associated genetic pathways, whilst assuring fillet nutritional value for human consumption.

Black soldier fly (Hermetia illucens) larvae meal in diets of European seabass: Effects on antioxidative capacity, non-specific immunity, transcriptomic responses, and resistance to the challenge with Vibrio alginolyticus

Black soldier fly larvae meal (BSFLM) has been successfully demonstrated as a promising fish meal (FM) replacer in diets of several fish species including European seabass (Dicentrarchus labrax). However, its impacts on antioxidant capacity, and immune responses of treated fish are still poorly understood. A 60-day feeding trial was carried out to evaluate the effects of partial substitution of FM with different levels of dry BSFLM on the antioxidative status, non-specific immunity, transcriptomic responses, and resistance of European seabass to the challenge with Vibrio alginolyticus. Four isoproteic (45%) and isolipidic diets were formulated by replacing 0.0%, 25%, 35%, and 50% of the dietary FM. Each diet was randomly assigned to four fish groups (in triplicates) (initial mean body weight, 12.1 ± 0.21 g) (20 fish per aquarium) (n = 240). Fish were fed three times daily to the apparent satiation. At the end of the feeding trial, serum antioxidant biomarkers such as malondialdehyde levels, and catalase, superoxide dismutase, and glutathione peroxidase enzyme activities were significantly increased in all BSFLM groups in a dose-dependent manner compared to the control group (P < 0.05). The non-specific immune indices, including phagocytic activity, phagocytic index, serum lysozyme and respiratory burst activities were significantly elevated in BSFLM groups compared to those in the control group (P < 0.05). Significant upregulation of the mRNA expression levels of hepatic heat shock protein 70, interleukin-1beta and interleukin-10 genes were observed in all BSFLM groups compared to the control group (P < 0.05). Additionally, after the challenge with V. alginolyticus, the relative percent of survival was significantly elevated in fish groups fed on diets containing graded levels of BSFLM over the control group (P < 0.05). Conclusively, the present study suggests the potential efficacy of partial replacement of dietary FM protein for up to 50% by BSFLM without negative effects on fish health with possible potentiation of the antioxidative status, and the immune responses of the European seabass.

The Feasibility of Using Yellow Mealworms (Tenebrio molitor): Towards a Sustainable Aquafeed Industry

Simple Summary

The expansion of the aquaculture industry depends mainly on aquafeed availability at reasonable prices. The common ingredients of aquafeed (e.g., fish and soybean meals) are not sustainable due to a lack of resources and increasing prices. Seeking alternative non-traditional ingredients is among the choices of nutritionists to produce high-quality feed at a feasible cost. Yellow mealworms (Tenebrio molitor) (TM) have been introduced to the feed industry as protein sources of a circular economy. Many studies have investigated the possibility of including T. molitor meals as a substitute for fish and soybean meals in aquafeed. Thus, this review exclusively presents an assemblage of the literature on the possibility of including T. molitor in aquafeed as a suggestion for the sustainability of the aquaculture industry.

Abstract

The success of the aquafeed industry mainly depends on the availability of raw ingredients with high nutritional value, such as fishmeal (FM). However, the increased demand for FM elevates its prices and leads to high feed costs. Thus, there is an urgent need to find suitable alternatives for FM in fish diets to achieve sustainability in aquaculture. Currently, attention is being paid to the possibility of using insect meals as FM substitutes in aquafeed because of their relatively high nutritional quality. TM is one of those insects that can be regarded as a unique candidate because of its relatively high nutritional value. TM are rich sources of essential amino acids (methionine), lipids, and fatty acids, which vary based on the developmental stage of the worms. Although TM have an abundant amount of chitin as a fiber source and other anti-nutritional factors, numerous studies have investigated the efficacy of partial or complete substitution of FM by T. molitor in fish diets. In this context, we reviewed the current research findings on the achievable inclusion levels of T. molitor versus FM substitution in the diets of several finfish and shellfish species. We discussed the potential use of T. molitor as an FM substitute in fish diets and evaluated its effects on growth, biometric indices, and body composition. Besides, the hematological parameters, immunological responses, antioxidative efficacy, intestinal health status, and sensory criteria of fish fed T. molitor-based diets were also assessed.

'Insects as Food and Feed: If You Can't Beat Them, Eat Them!'-To the Magnificent Seven and Beyond

The objective of this special issue is to highlight the current state of research in the field of insects as food and feed, but also other aspects on the exploitation of insect farming. In this editorial, we make a short introduction of the topic of the special issue, briefly present the contributions that are collected in it and offer some thoughts on the future research priorities and challenges that should be addressed. Regarding insect farming, there are additional applications, such as fertilizer, health-promoting products, and cosmetics, that can be produced and utilized, that go far beyond food and feed production.

Effects of full replacement of dietary fishmeal with insect meal from Tenebrio molitor on rainbow trout gut and skin microbiota

Background

Aquaculture must continue to reduce dependence on fishmeal (FM) and fishoil in feeds to ensure sustainable sector growth. Therefore, the use of novel aquaculture feed ingredients is growing. In this regard, insects can represent a new world of sustainable and protein-rich ingredients for farmed fish feeds. Accordingly, we investigated the effects of full replacement of FM with Tenebrio molitor (TM) larvae meal in the diet of rainbow trout (Oncorhynchus mykiss) on fish gut and skin microbiota.

Methods

A feeding trial was conducted with 126 trout of about 80 g mean initial weight that were fed for 22 weeks with two isonitrogenous, isolipidic, and isoenergetic extruded experimental diets. Partially defatted TM meal was included in one of the diets to replace 100% (TM 100) of FM, whereas the other diet (TM 0) was without TM. To analyse the microbial communities, the Illumina MiSeq platform for sequencing of 16S rRNA gene and Qiime pipeline were used to identify bacteria in the gut and skin mucosa, and in the diets.

Results

The data showed no major effects of full FM substitution with TM meal on bacterial species richness and diversity in both, gut mucosa- and skin mucus-associated microbiome. Skin microbiome was dominated by phylum Proteobacteria and especially by Gammaproteobacteria class that constituted approximately half of the bacterial taxa found. The two dietary fish groups did not display distinctive features, except for a decrease in the relative abundance of Deefgea genus (family Neisseriaceae) in trout fed with insect meal. The metagenomic analysis of the gut mucosa indicated that Tenericutes was the most abundant phylum, regardless of the diet. Specifically, within this phylum, the Mollicutes, mainly represented by Mycoplasmataceae family, were the dominant class. However, we observed only a weak dietary modulation of intestinal bacterial communities. The only changes due to full FM replacement with TM meal were a decreased number of Proteobacteria and a reduced number of taxa assigned to Ruminococcaceae and Neisseriaceae families.

Conclusions

The data demonstrated that TM larvae meal is a valid alternative animal protein to replace FM in the aquafeeds. Only slight gut and skin microbiota changes occurred in rainbow trout after total FM replacement with insect meal. The mapping of the trout skin microbiota represents a novel contribution of the present study. Indeed, in contrast to the increasing knowledge on gut microbiota, the skin microbiota of major farmed fish species remains largely unmapped but it deserves thorough consideration.

Mealworm (Tenebrio molitor Larvae) as an Alternative Protein Source for Monogastric Animal: A Review

Simple Summary

Tenebrio molitor (T. molitor) larvae, known as mealworm, have been considered a good protein source for monogastric animals. They have a high quantity and quality of protein content and amino acid profile. The inclusion of T. molitor larvae in broiler diets improved the growth performance without having negative effects on carcass traits and blood profiles in broiler chickens, or had no influence on the growth performance and carcass yield of broiler chickens. The supplementation of T. molitor larvae improved the growth performance and protein utilization of weaning pigs. Furthermore, the replacement of fishmeal with T. molitor larvae resulted in no difference in the growth performance and nutrient digestibility of weaning pigs. However, there are some challenges regarding biosafety, consumer’s acceptance, and price for the use of T. moiltor larvae in animal feed. Consequently, T. molitor larvae could be used as an alternative or sustainable protein source in monogastric animal feed.

Abstract

Edible insects have been used as an alternative protein source for food and animal feed, and the market size for edible insects has increased. Tenebrio molitor larvae, also known as mealworm and yellow mealworm, are considered a good protein source with nutritional value, digestibility, flavor, and a functional ability. Additionally, they are easy to breed and feed for having a stable protein content, regardless of their diets. Therefore, T. molitor larvae have been produced industrially as feed for pets, zoo animals, and even for production animals. To maintain the nutrient composition and safety of T. molitor larvae, slaughtering (heating or freezing) and post-slaughtering (drying and grinding) procedures should be improved for animal feed. T. molitor larvae are also processed with defatting or hydrolysis before grinding. They have a high quality and quantity of protein and amino acid profile, so are considered a highly sustainable protein source for replacing soybean meal or fishmeal. T. molitor has a chitin in its cuticle, which is an indigestible fiber with positive effects on the immune system. In studies of poultry, the supplementation of T. molitor larvae improved the growth performance of broiler chickens, without having negative effects on carcass traits, whereas some studies have reported that there were no significant differences in the growth performance and carcass yield of broiler chickens. In studies of swine, the supplementation of T. molitor larvae improved the growth performance and protein utilization of weaning pigs. Furthermore, 10% of T. molitor larvae showed greater amino acid digestibility than conventional animal proteins in growing pigs. However, there are some challenges regarding the biosafety, consumer’s acceptance, and price for the use of T. moiltor larvae in animal feed. Consequently, T. molitor larvae could be used as an alternative or sustainable protein source in monogastric animal feed with a consideration of the nutritional values, biosafety, consumer’s acceptance, and market price of T. molitor larvae products.

Ontogenic Development of Digestive Enzymes in Mealworm Larvae (Tenebrio molitor) and Their Suitable Harvesting Time for Use as Fish Feed

Mealworm larvae (Tenebrio molitor) are edible insects consumed in feed and food. In the current study, the optimal harvesting time of mealworm larvae for use as aquafeed was investigated during the ages of 30-90 days after hatching (DAH). Development of digestive enzymes, proximate composition, and in vitro protein digestibility using digestive enzymes from African catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus), were used as criteria. The specific activities of pepsin and trypsin significantly decreased with age (p < 0.05) from the first harvesting time until 50 and 45 DAH, respectively, while steadiness in these enzyme activities was observed onwards. Chymotrypsin specific activity appeared constant across all harvesting times. The specific activity of amylase significantly decreased in the later stages of development, while cellulase exhibited a different pattern suggesting it has a major role in dietary fiber utilization relative to starch. Regarding proximate compositions of the mealworm larvae, the moisture and ash contents decreased significantly with age, while the protein content exhibited the opposite trend with the highest contents from 60 to 90 DAH. Crude lipid was generally fairly constant, but its lowest value was observed in the earliest stage. In vitro protein digestibility was not significantly different across all harvesting times for both fish species, except for the significantly decreased digestibility value at 65 DAH relative to 30 and 35 DAH for Nile tilapia. However, based on the economic benefits of time for growth increment and proximate chemical composition, approximately 60 DAH is proposed as suitable for harvesting mealworm larvae to be used in fish feed.

Defatted Tenebrio molitor Larva Fermentation Extract Modifies Steatosis, Inflammation and Intestinal Microflora in Chronic Alcohol-Fed Rats

This study examined the effects of defatted mealworm fermentation extract (MWF) on alcoholic liver injury in rats. The rats were fed either a Lieber-DeCarli control (Con) or alcohol liquid diet (EtOH). The alcohol-fed rats were administered MWF (50, 100, or 200 mg/kg/day) and silymarin (200 mg/kg/day) orally for eight weeks. MWF prevented alcohol-induced hepatocellular damage by decreasing their serum aspartate transaminase, alanine transaminase, and gamma-glutamyl transpeptidase levels significantly compared to the EtOH group. MWF effectively reduced the relative hepatic weight, lipid contents, and fat deposition, along with the down-regulation of transcriptional factors and genes involved in lipogenesis compared to the EtOH group. It also enhanced the antioxidant defense system by elevating the glutathione level and glutathione reductase activity. MWF attenuated the alcohol-induced inflammatory response by down-regulating hepatic inflammation-associated proteins expression, such as phosphorylated-inhibitor of nuclear factor-kappa B-alpha and tumor necrosis factor-alpha, in chronic alcohol-fed rats. Furthermore, sequencing analysis in the colonic microbiota showed that MWF tended to increase Lactobacillus johnsonii reduced by chronic alcohol consumption. These findings suggest that MWF can attenuate alcoholic liver injury by regulating the lipogenic and inflammatory pathway and antioxidant defense system, as well as by partially altering the microbial composition.

Fish Oil and Fish Meal Production from Urban Fisheries Biomass in Japan

Finding an alternative feed source for the replacement of fish oil (FO) and fish meal (FM) produced from whole fish has been an important issue for realizing sustainable aquaculture. In this study, fishery by-products generated in the distribution phase, known as urban fisheries biomass (UFB), were focused on. The quality parameter and nutrient components of FO and FM from UFB were analyzed. Although crude FO produced from UFB showed relatively poor quality properties, the refinement process made an improvement of the quality to make it comparable to commercially available FO. There is no big variation in several samples in fatty acid profiles of FO and amino acid profiles of FM, and they seem to be able to replace FO and FM from whole fish in the diet for cultured fish. The utilization of UFB should be promoted in economic and ecologic aspects; however, in use of the FM, there remains a risk of intra-species recycling that might lead to transmissible spongiform encephalopathy. Furthermore, we must take into consideration the possibility of contamination of fishery products from at-risk species and illegal, unreported, and unregulated (IUU) fisheries due to the lack of regulations in Japan.

Partially Defatted Tenebrio molitor Larva Meal in Diets for Grow-Out Rainbow Trout, Oncorhynchus mykiss (Walbaum): Effects on Growth Performance, Diet Digestibility and Metabolic Responses

Simple Summary

The current developments in the aquaculture sector have highlighted the need to find sustainable ingredients to replace fishmeal as a protein source in fish feeds. The use of insect meals may be a valid option, due to their good nutritional values and low ecological footprint. In this study, we evaluated the effects of a progressive fishmeal substitution with increasing concentrations of a partially defatted yellow mealworm meal in rainbow trout diets. We observed that the total substitution of fishmeal with insect meal is feasible and that there are no negative effects on fish growth or on the digestibility of most nutrients. The activities of hepatic enzymes involved in the amino acid metabolism and lipid synthesis were also evaluated. The enzymatic activities were not negatively influenced by insect meal inclusion in the diets. These results are of practical application for feed manufacturers and farmers, as they support the inclusion of insect meals in fish diets to obtain sustainable feeds that able to support an increase in aquaculture production.

Abstract

Insect meals are good candidates to replace fishmeal as new protein sources in aquafeeds. This study evaluated the effects of fishmeal replacement with different dietary inclusion levels of a partially defatted Tenebrio molitor (L.) larva meal (TM) on rainbow trout (Oncorhynchus mykiss Walbaum) growth, diet digestibility, and hepatic intermediary metabolism. A 154-day growth trial was performed with 252 rainbow trout (78.3 ± 6.24 g) randomly divided into twelve tanks and fed four experimental diets containing increasing levels of TM: 0% (TM0), 25% (TM25), 50% (TM50), and 100% (TM100) of fishmeal substitution, corresponding to TM dietary inclusion levels of 0%, 5%, 10%, and 20%, respectively. A digestibility trial was performed feeding 180 rainbow trout (94.6 ± 7.31 g) with the experimental diets used in the growth trial. The growth parameters were not affected by TM dietary inclusion. Regarding the evaluated apparent digestibility coefficients (ADC), only the ADC of crude protein was affected, showing the following trend: TM0 = TM25 > TM50 > TM100. The activities of key hepatic amino acid catabolic and lipogenic enzymes were not affected by the dietary composition. The results suggest that a partially defatted TM could totally replace fishmeal in commercial rainbow trout diets without negative effects on fish performance.

The Dipterose of Black Soldier Fly (Hermetia illucens) Induces Innate Immune Response through Toll-Like Receptor Pathway in Mouse Macrophage RAW264.7 Cells

In our study, a novel bioactive polysaccharide was identified in the larvae of the black soldier fly (BSF) (Hermetia illucens) as a molecule that activates the mammalian innate immune response. We attempted to isolate this molecule, which was named dipterose-BSF, by gel-filtration and anion-exchange chromatography, followed by nitric oxide (NO) production in mouse RAW264.7 macrophage cells as a marker of immunomodulatory activity. Dipterose-BSF had an average molecular weight of 1.47 × 10⁵ and consisted of ten monosaccharides. Furthermore, in vitro assays demonstrated that dipterose-BSF enhanced the expression of proinflammatory cytokines and interferon β (IFNβ) in RAW264.7 cells. The inhibition of Toll-like receptor 2 (TLR2) and 4 (TLR4) significantly attenuated NO production by dipterose-BSF, indicating that dipterose-BSF stimulates the induction of various cytokines in macrophages via the TLR signaling pathway. This observation was analogous with the activation of nuclear factor kappa B in RAW264.7 cells after exposure to dipterose-BSF. Our results suggest that dipterose-BSF has immunomodulatory potential through activating the host innate immune system, which allows it to be a novel immunomodulator for implementation as a functional food supplement in poultry, livestock, and farmed fish.

Housefly (Musca domestica) Larvae Preparations after Removing the Hydrophobic Fraction Are Effective Alternatives to Fish Meal in Aquaculture Feed for Red Seabream (Pagrus major)

Insects are an attractive alternative to fish meal (FM) as a sustainable protein source in aquaculture feed that does not negatively impact the marine ecosystem. Despite housefly (Musca domestica) larvae having adequacy of amino acid profiles, they have sometimes been reported to be inferior to FM, especially for marine carnivorous fish species. Here, we report that the removal of the hydrophobic fractions from housefly larvae enables significant replacement of FM in the diet of the red seabream (Pagrus major). In a feeding trial, housefly (HF) larvae that had the hydrophobic fraction removed as a complete substitution for 70% FM produced satisfactory growth. However, HF larvae that were supplemented with the hydrophobic fraction resulted in significant growth reduction. Growth recovery was incomplete by supplementation of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) to undefatted HF larvae, being equivalent to that of fatty acid content with a control diet. Moreover, fish with a dietary intake of catechol identified from the hydrophobic fraction of the HF showed growth reduction and morphological alterations in the intestine. Our findings indicate that the hydrophobic fraction from HF larvae contains a negative factor for fish growth and eliminating the fraction from HF larvae is thought to be an important process for sustainable aquaculture.

Replacing Fish Meal with Defatted Insect Meal (Yellow Mealworm Tenebrio molitor) Improves the Growth and Immunity of Pacific White Shrimp (Litopenaeus vannamei)

Recently, ecological and economic issues have affected fish meal (FM) supply, the main source of protein for shrimp. This triggered a search for alternative dietary protein sources for shrimp production. We studied the consequences of replacing FM with a defatted insect meal, ŸnMealTM (YM), comprised of yellow mealworm (Tenebrio molitor). Growth and immune parameters of juvenile Pacific white shrimp (Litopenaeus vannanmei) were compared after an eight-week feeding trial. Shrimp were kept in aquaria with densities of 60 and 40 shrimp/m2 and fed one of five diets in which a proportion of FM was replaced by YM. All diets were isoproteic, isoenergetic, and balanced in lysine and methionine. After the feeding trial, shrimp were challenged with pathogenic bacteria (Vibrio parahaemolyticus). Growth and feed conversion parameters improved when YM was included in shrimp diets; with the highest weight gain and best food conversion ratio (FCR) achieved when 50% of FM was replaced by YM versus the control diet that contained no YM (initial weight: 1.60 g/shrimp; growth: 5.27 vs. 3.94 g/shrimp; FCR 1.20 vs. 1.59). In challenged shrimp, mortality rates were significantly less among groups that received YM, with a 76.9% lower mortality rate in the 50% FM replacement group versus the control.