Fishmeal Alternative Protein Sources for Aquaculture Feeds

The Addition of Hermetia illucens to Feed: Influence on Nutritional Composition, Protein Digestion Characteristics, and Antioxidant Activity of Acheta domesticus

As sales have increased in recent years, enhancing production processes and quality has emerged as a significant challenge for the cricket industry. In this study, we investigated the impact of supplementing feed with black soldier fly larvae (BSFL) on the yield, nutritional characteristics, and protein digestibility of Acheta domesticus. In addition, the bioactivity of house cricket proteins was compared. The results demonstrated that incorporating BSFL into feed improved the yield and nutritional characteristics of house cricket, such as crude protein levels and total phenolic content. Alterations in amino acid and fatty acid profiles also enhanced their nutritional value. In addition, 5% BSFL and 10% BSFL were more readily digested, and the protein hydrolysate of the groups fed BSFL demonstrated stronger antioxidant activity. The findings of this study can offer valuable insights into house cricket farming, protein processing, and the development of new food products.

Defatted black soldier fly (Hermetia illucens) diets improved hemato-immunological responses, biochemical parameters, and antioxidant activities in Streptococcus iniae-infected Nile tilapia (Oreochromis niloticus)

BACKGROUND

Challenges of limited supply and increasing prices of fishmeal have driven the aquaculture nutritionists to seek alternative sustainable protein rich ingredients to keep manufacturing aquafeeds in a maintainable and cost-effective way. Black soldier fly, Hermetia illucenslarvae meal represent great potential as a sustainable alternative to fishmeal in aquafeeds.

METHODS

Three replacement diets for fishmeal were prepared at different levels of defatted black soldier fly (Hermetia illucens) meal (DBSFM): Diet 1 (0 g DBSFM /kg diet, control), 33% (DBSFM-33%, 66 g DBSFM /kg diet), and 100% (DBSFM-100%, 200 g DBSFM /kg diet) to investigate their effects on biochemical parameters, immuno-hematological responses, antioxidant activities, and inflammatory gene expression in Nile tilapia, Oreochromis niloticus, a total of 270 (40.0 ± 0.50 g) before and after challenge with Streptococcus iniae (S. iniae). The feeding trial lasted six weeks (pre-challenge) and two weeks (post-challenge).

RESULTS

The results showed a significant improvement in white blood cell count (P < 0.01), lymphocyte count (P < 0.01), serum lysozyme activity (P < 0.001), and phagocytic activity (P < 0.001), mostly in the DBSFM-100% group following the pre-challenge phase compared to the control group. Post-challenge phase exhibited significant increases in blood indices in the DBSFM-treated groups compared to the control group. Following pre- and post-challenge periods, both DBSFM-supplemented groups experienced significant increases (P < 0.01, P < 0.001), in serum total protein levels. Albumin and globulin levels also experienced similar increases (P < 0.05, P < 0.01), but only post-challenge. Total antioxidant capacity exhibited a significant increase in both DBSFM-supplemented groups following the post-challenge, as did superoxide dismutase, catalase, and glutathione peroxidase in the liver and spleen. Conversely, levels of glucose, cortisol, and malondialdehyde followed the opposite trend. DBSFM-100% inclusion revealed significant (P < 0.05) up-regulation of interleukin 1β (IL-1β) in the pre-challenge phase compared to control, but no significance (P > 0.05) was seen for other genes. Anti-inflammatory-related genes transforming growth factor-β and interleukin-10 mRNA expression levels were up-regulated in DBSFM-supplemented groups compared to the control post-challenge, but the opposite was seen for IL-1β and tumor necrosis factor- α.

CONCLUSION

These findings suggest that Nile tilapia challenged with S. iniae may experience significant enhancements in hemato-immunological parameters, antioxidant capability, and anti-inflammatory gene expression when fish meal is replaced with DBSFM up to 100%.

Exploring single cell microbial protein as a sustainable fishmeal alternative in yellowtail kingfish (Seriola lalandi) diets: impacts on health and gut microbiome

BACKGROUND

With the global expansion of aquaculture and the increasing demand for fish meal, identifying appropriate and sustainable alternative protein sources for aquafeeds has become essential. Single-cell protein (SCP), derived from methanotrophic bacteria, presents a promising alternative by converting methane into protein, potentially addressing both the need for alternative protein sources and reducing industrial greenhouse gas emissions. This study aimed to evaluate the effects of different levels of SCP inclusion (0%, 25%, 50%, and 75% fish meal replacement) on the health, gene expression, and gut microbiome of yellowtail kingfish (YTK, Seriola lalandi) following a 35-day growth trial.

RESULTS

The study found that SCP inclusion at the highest level of fishmeal replacement (75%) induced a mild inflammatory response in the hindgut of the fish. However, micromorphological assessments of the hindgut, serum biochemistry, and gene expression analyses revealed no significant detrimental effects from SCP replacement. Notably, there were indications of improved lipid digestibility with SCP. Furthermore, SCP inclusion significantly enhanced microbial richness and altered the composition of the gut microbiome, introducing beneficial bacterial taxa that may contribute to improved gut health and resilience.

CONCLUSIONS

This study highlights SCP as a viable and sustainable alternative to fish meal in YTK diets. The findings suggest that SCP can be included in YTK diets without adverse health effects at moderate levels and may even offer benefits in terms of lipid digestibility and gut microbiome diversity. These results contribute to the advancement of more sustainable aquaculture practices.

Using a blend of oilseed meals in the diets of Nile tilapia (Oreochromis niloticus): effects on the growth performance, feed utilization, intestinal health, growth, and metabolic-related genes

In this study, Nile tilapia were fed a blend of oilseed meals (BOM) that includes cottonseed meal (CSM), linseed meal (LSM), sesame meal (SSM), and sunflower meal (SFM) at a ratio of 1 CSM: 1 LSM: 1 SSM: 1 SFM. Six diets were formulated where the first diet included FM and SBM as protein sources and considered the positive control diet (FM). Another five FM-free diets were formulated, where SBM was substituted with BOM and included at 0, 100, 200, 300, and 400 g/kg diet. After 90 days, the FBW, WG, and PER were markedly increased while FCR decreased by FM-based diet and BOM at 0, 100, or 200 g/kg compared to fish-fed BOM at 300, and 400 g/kg (P < 0.05). The groups treated with BOM at 100-200 g/kg demonstrated considerable impairments, followed by those treated with BOM at 300 g/kg. Furthermore, fish given BOM at 400 g/kg had significantly less intestinal histological characteristics than the other groups. The relative expression of the IGF-1, GHR1, FABP, and CCK genes were downregulated in tilapia-fed BOM at 200, 300, and 400 g/kg compared to fish-fed FM-based diet (P < 0.05). The relative cost of feed per kg fish gain showed 4.42, 7.11, 8.14, 10.32, and 8.10% reduction rates in fish-fed SBM, or BOM at 100, 200, 300, and 400 g/kg. In conclusion, dietary BOM can be incorporated in Nile tilapia diets at up to 200 g/kg without affecting growth performance or feed utilisation. High inclusion levels (300 and 400 g/kg) may impair growth performance and feed utilisation by disrupting intestinal histological characteristics and reducing expression of growth and metabolic genes (GHR1, IGF-1, FABP, and CCK) in the liver.

The Biotechnological Potential of Crickets as a Sustainable Protein Source for Fishmeal Replacement in Aquafeed

As aquaculture production grows, so does the demand for quality and cost-effective protein sources. The cost of fishmeal (FM) has increased over the years, leading to increased production costs for formulated aquafeed. Soybean meal (SBM) is commonly used as an FM replacer in aquafeed, but anti-nutritional factors could affect the growth, nutrition, and health of aquatic organisms. Cricket meal (CM) is an alternative source with a nutrient profile comparable to FM due to its high protein content, digestibility, and amino acid profile. CM use in aquafeed influences growth and reproductive performance while modulating the gut microbiota and immune response of fish and shrimp. However, consistent regulation and scaling up are necessary for competitive prices and the marketing of CM. Moreover, the chitin content in CM could be an issue in some fish species; however, different strategies based on food biotechnology can improve the protein quality for its safe use in aquafeed.

Inclusion Impact of Jack Mackerel Meal in the Red Sea Bream (Pagrus major) Feeds Replacing Various Animal Protein Sources for Fish Meal

This study aims to elucidate manipulation impacts of jack mackerel meal (JMM) in the red sea bream (Pagrus major) feeds replacing various animal protein sources for different levels of fish meal (FM) on growth and feed availability. Two-way ANOVA experimental design was applied with three substitution sources: animal protein sources (tuna byproduct meal (TBM), chicken byproduct meal (CBM), and meat meal (MM)) and two FM substitution levels (25% and 50%). The control (Con) diet contained 60% FM. In the Con diet, 25% and 50% of FM were replaced with TBM, CBM, and MM, respectively, and then 24% jack mackerel meal (JMM) was included at the expense of FM, named as the TBM25, TBM50, CBM25, CBM50, MM25, and MM50 diets, respectively. Red sea bream juveniles averaging 11.8 g were distributed in 21 flow-through tanks (20 fish per tank) with triplicate. Fish were carefully hand-fed to apparent satiation for 8 weeks. At the end of the 8-week feeding experiment, the TBM-substituted diets produced significantly (P < 0.0001 for all) greater weight gain, specific growth rate (SGR), and feed consumption of fish than the CBM- and MM-substituted diets. Furthermore, dietary substitution of 25% FM achieved significantly (P < 0.0001, P < 0.0001, and P < 0.0003, respectively) greater weight gain, SGR, and feed consumption than dietary substitution of 50% FM based on two-way ANOVA analysis. Fish fed the TBM50 diet achieved the greatest weight gain, SGR, and feed consumption. Protein retention, biological indices, plasma and serum parameters, and the whole body chemical composition and amino acid (AA) profiles of red sea bream were not significantly influenced by dietary treatments. The TBM-substituted diets achieved significantly (P < 0.0001) greater economic profit index (EPI) than the CBM- and MM-substituted diets. Furthermore, dietary substitution of 25% FM achieved significantly (P < 0.002) greater EPI than dietary substitution of 50% FM. The TBM50 diet produced the greatest EPI. In conclusion, TBM and MM and CBM could replace 50% and 25% FM in the feeds with 24% JMM inclusion, respectively, without compromising the growth, feed utilization, plasma and serum parameters, chemical composition and AA profiles of red sea bream, and EPI. The TBM50 diet was the most desirable treatment in terms of the greatest growth performance of red sea bream and the highest economic return to farmer.

Improving Yellow Mealworm (Tenebrio molitor) Utilization with Sodium Butyrate in Nile Tilapia Diets: Effects on Growth Performance, Intestinal Histology, Antioxidative Response, and Blood Biomarkers

Yellow mealworm (Tenebrio molitor) meal was introduced to aquafeed as a suitable protein source to replace fish meal (FM) and soybean meal and, thereby, consistent aquaculture production. However, mealworms should be added at adequate levels due to the presence of antinutritional factors such as chitin. Consequently, sodium butyrate (SB) is suggested to improve feed quality and ensure aquatic animals' productivity and welfare. In this study, parallel with the protein source (T. molitor meal or FM), dietary supplementation of SB (1 g/kg) is involved as a factor in the 2 × 2 factorial study. The first and the second diets were formulated using FM as a protein source with or without SB, while the third and fourth diets were prepared by replacing FM with T. molitor meal with or without SB supplementation. After 60 days, fish fed with FM or T. molitor and SB showed improved final body weight and weight gain, while those fed with T. molitor without SB had a reduced protein efficiency ratio. Histological analysis revealed that dietary SB improved intestinal histological features by increasing the height and branching of intestinal villi and immune cell infiltration near intestinal crypts in Nile tilapia-fed FM or T. molitor. Furthermore, fish-fed FM or T. molitor and SB had higher Hb, red blood cells, PCV, total protein, and globulin levels than fish-fed respective test diets without SB supplementation. Dietary SB addition to FM or T. molitor-based diets also significantly enhanced blood lysozyme and phagocytic activities, catalase, superoxide dismutase, glutathione peroxidase, and reduced MDA levels. Our results demonstrate that T. molitor meal can replace FM without compromising Nile tilapia's growth performance and health status. Additionally, SB supplementation improved T. molitor meal utilization by Nile tilapia, thereby significantly enhancing the growth, digestion capacity, intestinal histological features, and antioxidative and immune responses. Consequently, dietary T. molitor meal reduces the reliance on FM and improves the sustainability and efficiency of Nile tilapia production.

Growth and Hepatopancreas Health of Juvenile Chinese Mitten Crab (Eriocheir sinensis) Fed Different Levels of Black Soldier Fly (Hermetia illucens) Larvae Meal for Fish Meal Replacement

A 56-day feeding trial assessed the effects of black soldier fly larvae meal (BSFLM) on the growth performance and hepatopancreas health of juvenile Eriocheir sinensis. Six isoproteic and isolipidic diets with 0% (FM), 10% (BSFLM10), 20% (BSFLM20), 30% (BSFLM30), 40% (BSFLM40), or 50% (BSFLM50) replacement of fish meal by BSFLM were formulated. Compared to FM, replacing 10%-40% of fish meal with BSFLM did not significantly affect the weight gain rate (WGR) or specific growth rate (SGR), while BSFLM50 significantly decreased the WGR and SGR. Crabs fed BSFLM50 had significantly lower T-AOC activity than those fed other diets, and crabs fed BSFLM30, BSFLM40, or BSFLM50 had significantly lower activities of antioxidant enzymes (SOD and GSH-Px) in the hepatopancreas than those fed FM or BSFLM10. Compared to FM, BSFLM10, BSFLM20, and BSFLM30 did not affect the relative expression of genes related to the nonspecific immunity, while BSFLM40 and BSFLM50 upregulated the relative expression of these genes. Furthermore, histological analysis showed that the hepatopancreas was deformed in the BSFLM50 group, with widened lumens and loss of basal membrane integrity. In summary, BSFLM replacing 50% of fish meal reduced growth and structural damage to the hepatopancreas. An immune response was activated when the replacement level was over 30%. Therefore, the replacement level of dietary fish meal by BSFLM is recommended to be not more than 30% of the juvenile E. sinensis feed.

The effects of dietary microbial 6-phytase on growth parameters, intestinal morphometric properties and selected intestinal genes expression in rainbow trout (Oncorhynchus mykiss, Walbaum 1876)

This study investigated the effects of dietary 6-phytase, produced by a genetically modified Komagataella phaffii, on growth performance, feed utilisation, flesh quality, villus morphometric properties, and intestinal mRNA expression in rainbow trout. Six iso-nitrogenous, iso-lipidic, and iso-caloric diets were formulated and fed to triplicate groups of juvenile rainbow trout weighing 32.57 ± 0.36 g (mean ± SD) for 90 days. The dietary treatments included two positive controls (PC), one formulated with 400 g/kg of fish meal named T1, and the other formulated with 170 g/kg of fish meal plus 1% avP derived from monocalcium phosphate named T2. The remaining dietary treatments consisted of a negative control (NC) formulated with 170 g/kg of fish meal (T3), NC+ 750, NC+ 1500, and NC+ 3000 OTU/kg levels of phytase designated as T4, T5, and T6 diets respectively. Compared to T1, weight gain (WG) increased by 16.29, 13.71 and 11.66% in T4, T5 and T6, respectively (p < 0.05). Feed conversion ratio (FCR) was lowered by 3.2 and 0.8% in T4 and T5 compared to T1 (p < 0.05). WG, feed intake (FI), FCR, final body length, bone ash, bone ash P, and intestinal morphometry were negatively affected in T3 fed fish (p < 0.05). Whole-body fish nutrient, bone ash, bone ash phosphorus (P) compositions and mucosal villus morphometric properties improved in rainbow trout fed diets supplemented with phytase dose ranging from 750-3000 OTU. Bone ash increased by 6.12% in T5 compared to T1 (p < 0.05). Phytase inclusion enhanced the profitability of feeding juvenile rainbow trout such diets as it reduced the feed price and economic conversion rate. Dietary inclusion of phytase down-regulated mRNA expression of genes responsible for fatty acid synthesis and lipogenesis in juvenile rainbow trout. Dietary phytase up-regulated the mRNA expression of genes (SLC4A11 and ATP1A3A) responsible for nutrient uptake and down-regulated intestinal expression of MUCIN 5AC-like genes (mucus secreting genes) in juvenile rainbow trout. Along with improving performance parameters, the inclusion of phytase in rainbow trout diet containing plant-based protein sources, can preserve intestinal morphology by regulating the mRNA expression of genes responsible for fatty acid synthesis, lipogenesis and nutrient uptake and transport.

Compared to Fishmeal, Dietary Soybean Meal Improves the Reproductive Performance of Female Yellow Catfish (Pelteobagrus fulvidraco) Broodstock

To investigate the effects of different dietary protein sources on the reproductive performance of female broodstock, yellow catfish (Pelteobagrus fulvidraco) were fed with three experimental diets using fishmeal (FM), soybean meal (SBM), and rapeseed meal (RSM) as main protein sources, respectively. Females (initial weight: 64.56 ± 0.45 g) were distributed into 9 net cages for feeding trial. Results indicated that 30% dietary SBM improved the reproductive performance for higher gonadosomatic index (GSI), relative fecundity, total egg production, egg diameter, and hatching rate. In addition, SBM and RSM diets resulted in higher estradiol (E2), vitellogenin (VTG), luteinizing hormones (LH), and lower follicle-stimulating hormone (FSH) and testosterone (T) in plasma (P < 0.05) of female broodstock. Dietary SBM and RSM also resulted in lower mesenteric fat index (MFI), plasma total cholesterol (TC), plasma total bilirubin (T-Bil) contents, and gonadal cortisol concentrations, while dietary SBM downregulated the transcription levels of steroidogenesis-related proteins by negative feedback (P < 0.05). The results demonstrated that dietary SBM and RSM could promote sex steroid hormone and VTG biosynthesis and showed hypocholesterolemic effects. Besides, 30% dietary SBM inclusion could improve the reproductive performance of female yellow catfish broodstock.

Inheritance of Two Traits With High Plasticity, Developmental Speed, and Body Size, in Tenebrio molitor (Coleoptera: Tenebrionidae)

The study of inheritance of quantitative traits of high plasticity in insects has been limited. The heritability of larval development time and body weight in Tenebrio molitor L. was determined using the method of parent-offspring regression. The parental group of adults obtained from a cohort from one day of oviposition from a stock colony was divided into 28 class groups according to their larval development time and pupal weight. The progeny resulting from these parental classes was grouped in experimental units and allowed to develop to the pupal stage. Means of larval development time and pupal weight of the progeny were compared with their parental class levels using linear regression. The selection of larval development time and pupal weight in the parental classes had a significant impact on the means of larval development time and pupal weight of the progeny. The regression coefficients for larval development time and pupal weight were 0.626 ± 0.02 and 0.408 ± 0.02, respectively. These values represent the proportion of genetic determination of these two traits based on the principles of the method of parent-offspring regression. The apparent independence of larval development time and pupal weight based on their poor linear correlation is discussed.

Black soldier fly full-fat meal in Atlantic salmon nutrition – Part A: Effects on growth performance, feed utilization, selected nutriphysiological traits and production sustainability in fries

Black soldier fly larva meal (BSFM) application as an innovative feed material has been developed in aquaculture nutrition. However, recent scientific literature is still lacking in the case of insect meal effects on different stages of salmonid fish, and the vast majority of research is focused on farmed Atlantic salmon. Therefore, the holistic approach was undertaken in the cycle of two studies carried out: on fries and pre-smolts. This study aimed to evaluate the effect of fish meal (FM) replacement by full-fat BSFM in Atlantic salmon fry diets on the growth performance, feed utilization, crude protein and crude fat digestibility, somatic indices, histomorphology of intestines, and environmental sustainability. Additionally, pellet quality was assessed. Two experiments were performed on 360 Atlantic salmon fries – each of which lasted 60 days. For the first experiment, 240 individuals were distributed to four experimental groups: six replicates (tanks) per group and 10 fish per tank. For the second experiment, 120 individuals were distributed to four experimental groups: three replicates (tanks) per group and 10 fish per tank were used. The following groups were applied: CON – without the addition of full-fat BSFM and with 39% FM; BSFM5 – with 5% addition of full-fat BSFM and 36.1% FM; BSFM10 – with 10% full-fat BSFM and 33.3% FM; BSFM15 – with 15% addition of full-fat BSFM and 30.3% FM. The present study showed satisfactory results of BSFM inclusion at the levels of 5% and 10% as a replacement for fish meal in feeds for Atlantic salmon fries. No negative effects on growth performance, feed utilization, protein and fat digestibility, or intestinal structure were recorded. Simultaneously, insect meal inclusion in Atlantic salmon diets significantly improved the environmental sustainability of the feed. In the case of BSFM15, decreases in body weight gain, protein lipid efficiency ratio, and lipid efficiency ratio, as well as increases in feed conversion ratio, were observed. Therefore, the use of shares higher than 10% of BSFM in Atlantic salmon fries may not be recommended.

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.

On the Compatibility of Fish Meal Replacements in Aquafeeds for Rainbow Trout. A Combined Metabolomic, Proteomic and Histological Study

The sustainable development of modern aquaculture must rely on a significant reduction of the fish meal (FM) used in aquafeed formulations. However, FM substitution with alternative ingredients in diets for carnivorous fish species often showed reduced nutrient absorption, significantly perturbed metabolisms, and histological changes at both hepatic and intestinal levels. In the present study, rainbow trout (Oncorhynchus mykiss) were fed three different experimental aquafeeds. A control diet with higher FM content (27.3%) than two test formulations in which FM was substituted with two more sustainable and promising alternatives: insect meal (Hermetia illucens larvae = 10.1%, FM = 11.6%) and poultry by-products meal (PBM = 14.8%; FM = 11.7%). Combined metabolomics and proteomics analyses of fish liver, together with histological examination of liver and intestine demonstrated that a well-balanced formulation of nutrients in the three diets allowed high metabolic compatibility of either substitution, paving the way for a deeper understanding of the impact of novel raw materials for the fish feed industry. Results show that the main metabolic pathways of nutrient absorption and catabolism were essentially unaltered by alternative feed ingredients, and also histological alterations were negligible. It is demonstrated that the substitution of FM with sustainable alternatives does not have a negative impact on fish metabolism, as long as the nutritional requirements of rainbow trout are fulfilled.

The first insight into full-fat superworm (Zophobas morio) meal in guppy (Poecilia reticulata) diets: a study on multiple-choice feeding preferences and growth performance

Insect meals are sustainable alternative protein sources in animal nutrition. However, the data in the topic of their application in petfood and ornamental fish nutrition are scarce. Thus the present study was undertaken to asses their usability in guppy (Poecilia reticulata) diets. The first experiment aimed to investigate the attractiveness of select insect meals for guppies, and the second in evaluation of superworm (Zophobas morio) meal monodiet effects. The first experiment (free-choice feeding test) lasted five days. Fish were given a choice between four attractants: fish meal, black soldier fly (Hermetia illuces) meal (HI), Madagascar cockroach (Gromphadorhina portentosa) meal (MC), and superworm (Zophobas morio) meal (ZM). The preliminary part of the study showed that the most frequently chosen attractant throughout the entire free-choice feeding test period was ZM. Based on the obtained results, the second part of the study was designed as a growth test with the use of a ZM monodiet compared to commercial feed. The experiment lasted 90 days, and 150 guppy fry were used. The fish were randomly divided into two groups (CON - commercial feed, ZM - Zophobas morio meal). No effects of dietary treatment were found in terms of survival rate, fish body length, or fish body length gain. The present study shows that ZM was the most preferred attractant and that a monodiet based on insect meal can be successfully applied in guppy fry nutrition.

Dietary inclusion of a partially defatted black soldier fly (Hermetia illucens) larva meal in low fishmeal-based diets for rainbow trout (Oncorhynchus mykiss)

Background

Recent investigations highlighted that Hermetia illucens (BSF) larva meal can be a valuable alternative protein source for aquafeed production. In this study, in substitution of fishmeal, we used increasing inclusion levels of a partially defatted BSF larva meal in low fishmeal-based diets for rainbow trout (Oncorhynchus mykiss Walbaum) and we evaluated the related implications in terms of growth performance, physical characteristics, proximate and fatty acid (FA) compositions of the fillets, gut and liver histology, and diet digestibility. In a 131-day trial, 576 fish (100.1 ± 9.29 g) were randomly allotted to 24 tanks (24 fish/tank, 4 replicates/treatment). Six experimental diets were produced to have partial replacement of fishmeal (0, 10%, 20%, 30%, 40% and 50%) by increasing levels of BSF meal (0% [BSF0], 3% [BSF3], 6% [BSF6], 9% [BSF9], 12% [BSF12] and 15% [BSF15] on as fed basis, respectively).

Results

No differences were observed among the treatments for all the considered growth performance parameters. The viscero and hepato-somatic indexes showed significant differences among the treatments, with the highest values observed in the BSF15 group. No differences were recorded in terms of fillet’s physical characteristics, dry matter (DM), crude protein (CP) and ether extract (EE) contents. Total saturated and monounsaturated FA increased, while polyunsaturated FA (particularly n-3 FA) decreased while increasing the HI meal inclusion in the diet. Histopathology of liver and gut was not affected, whereas, in posterior gut, villi were higher in BSF6 and BSF9 compared to BSF3 fish. The apparent digestibility of DM, CP, EE and gross energy did not vary among the treatments.

Conclusions

These results suggest that a partially defatted BSF meal could be included up to 15% in low fishmeal-based diets for rainbow trout with no adverse effects on growth performance, fillet’s physical characteristics, gut and liver health, and diet digestibility. On the contrary, the fillet FA composition worsened while increasing the level of BSF meal in the diet.

Minimizing marine ingredients in diets of farmed Atlantic salmon (Salmo salar): effects on liver and head kidney lipid class and fatty acid composition

Limited fish meal and fish oil supplies have necessitated research on alternatives for aquafeeds. Seven dietary treatments with different protein and lipid sources were formulated for farmed Atlantic salmon, and their effects on liver and head kidney lipid class, fatty acid, and elemental composition were studied. Fish meal, fish oil, and EPA + DHA content ranged from 5-35%, 0-12%, and 0.1-3%, respectively. Elemental analysis showed that the C to N ratio was higher in the head kidney than in the liver, which is consistent with higher content of total lipids in the head kidney compared with the liver. There was a greater susceptibility to dietary lipid alterations in the liver compared with the head kidney despite liver having a greater proportion of phospholipid and a much lower proportion of triacylglycerol. So long as fish oil levels were 5% or more of the diet, arachidonic acid (ARA) and docosahexaenoic acid (DHA) proportions were the same for each tissue as with feeding the marine diet with 12% fish oil; however, livers and head kidneys from fish fed the lowest amount of fish meal and fish oil had the lowest levels of eicosapentaenoic (EPA) and DHA and the highest ARA levels. Removal of fish oil and reduction of fish meal to 5% in diets of farmed Atlantic salmon affected elemental and lipid compositions of the liver and head kidney tissues potentially increasing susceptibility to inflammation. However, with 10% of the diet comprising fish meal and fish oil, lipid contents were comparable with fish fed marine-based diets.

Population Growth of Alphitobius diaperinus (Coleoptera: Tenebrionidae) on Various Commodities

The lesser mealworm, Alphitobius diaperinus (Panzer), is a serious pest, but at the same time has been authorized in European Union (EU) for feed in aquaculture. In this study, we investigated, in laboratory bioassays, the population growth of this species, on a wide variety of commodities. In four series of bioassays, we studied the development of A. diaperinus population on various intact cereal grains, on soft wheat grains with different percentages of cracked kernels, on non-grain amylaceous commodities and on a variety of non-amylaceous commodities. Briefly, 20 g of each commodity were put separately inside plastic cylindrical vials. Then, 20 A. diaperinus adults were placed inside each vial and all vials were incubated at 30°C and 55% r.h. After 30 d, the vials were opened and the progeny production was evaluated. Alphitobius diaperinus showed a clear preference in amylaceous commodities, but in contrast, poor development was recorded on the non-amylaceous commodities tested. Hence, it developed well in most of the cereal intact grains tested, with the hard and soft wheat being the most suitable. Additionally, most non-grain amylaceous commodities were suitable, to a various degree, for the population growth of A. diaperinus. The increase of the percentage of cracked wheat positively affected the population growth of A. diaperinus. To our knowledge, this is the first study that examined the suitability of a wide range of commodities for the population growth of A. diaperinus.

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.

Effect of dietary supplementation with insect fats on growth performance, digestive efficiency and health of rabbits

BACKGROUND

The present work aimed at evaluating the effect of the dietary replacement of soybean oil (S) by two types of insect fats extracted from black soldier fly larvae (H, Hermetia illucens L.) and yellow mealworm larvae (T, Tenebrio molitor L.) on growth performance, nutrient digestibility, blood parameters, intestinal morphology and health of growing rabbits.

METHODS

At weaning, 200 crossbred rabbits (36 days old) were allotted to five dietary treatments (40 rabbits/group): a control diet (C) containing 1.5% of soybean oil and four experimental diets where soybean oil was partially (50%) or totally (100%) substituted by H (H50 and H100) or T (T50 and T100) fats. Total tract digestibility was evaluated on 12 rabbits per treatment. The growth trial lasted 41 d and, at slaughtering (78 days old), blood samples were collected from 15 rabbits per treatment, morphometric analyses were performed on duodenum, jejunum and ileum mucosa, and samples of liver, spleen and kidney were submitted to histological evaluation.

RESULTS

No difference was observed between the control and the experimental groups fed insect fats in terms of performance, morbidity, mortality and blood variables. The addition of H and T fats did not influence apparent digestibility coefficients of dry matter, protein, ether extract, fibre fractions and gross energy. Gut morphometric indices and organ histopathology were not affected by dietary inclusion of H and T fats.

CONCLUSIONS

H and T fats are suitable sources of lipid in rabbit diets to replace soybean oil without any detrimental effect on growth performance, apparent digestibility, gut mucosa traits and health.