Abstract
This study evaluated the effects of diets containing Tenebrio molitor (TM) larvae meal on growth performances, somatic indexes, nutrient digestibility, dorsal muscle proximate and fatty acid (FA) compositions of rainbow trout. Three hundred sixty fish were randomly divided into three groups with four replicates each. The groups were fed diets differing in TM inclusion: 0% (TM0), 25% (TM25) and 50% (TM50) as fed weight basis. Weight gain was not affected by treatment. Feeding rate was significantly higher in TM0 than TM50. Feed conversion ratio was significantly higher in TM0 than TM25 and TM50, while an opposite trend was observed for protein efficiency ratio and specific growth rate. The survival rate was significantly lower in TM0 than TM25 and TM50. The apparent digestibility of protein was significantly lower in the TM50 group than the other groups, while the apparent digestibility of dry matter, organic matter and lipids was unaffected by treatment. If compared to control, the protein and lipid contents of fillets were respectively increased and decreased following TM inclusion in the diet. The Σn3/Σn6 FA ratio of fish dorsal muscle was linearly (TM0>TM25>TM50) reduced by TM inclusion in the diet. Results suggested that TM could be used during the growing phase in trout farming; however, additional studies on specific feeding strategies and diet formulations are needed to limit its negative effects on the lipid fraction of fillets.
Introduction
In aquaculture, the impressive growth of the use of fishmeal (FM) and fish oil (FO) in feeds for fish farming has jeopardized the sustainability of this production. About 61.3 and 9.9% of wild fish stocks worldwide are fully and under-fished, respectively (FAO, Citation2014). FM and FO productions seem therefore to have reached a maximum extent, cannot being able to fulfil the increasing world demand anymore (Shepherd and Jackson, Citation2013). The costs of FM and FO are influenced to a great extent by the available supplies of wild fish stocks, and, as a consequence, fish derivative products are currently the most expensive components of fish feed for aquaculture.
In the last twenty years, the price of FM has increased more than 400% and the trend is still increasing. Consequently, nowadays the main target of research studies in this field is to decrease the dietary level of fish derivative products, with potential associated benefits related to both the curtailment of feed costs and the face of global environmental issues.
The substitution of FM and FO by plant products is a common practice in fish aquaculture feeds (De Francesco et al., Citation2004; Palmegiano et al., Citation2005). Unfortunately, the use of plant products can lead to adverse effects, essentially attributable to their content of anti-nutritional factors and/or unpalatable compounds, inappropriate fatty acid (FA) profile, and shortage of essential amino acids (Gatlin et al., Citation2007; Gai et al., Citation2012).
The sustainability of insect production is also well documented; when the right farming temperature range is used, the feed conversion rate and the greenhouse gas production of insects are lower than those of other animals, since the former do not use energy to maintain their body temperature in a strict range. Consequently, the interest of researchers in the use of insect meal as aquaculture feed has been growing rapidly.
Recent reviews highlighted that meals derived from some insect larvae may provide adequate nutritional value for fish (Henry et al., Citation2015) as well as terrestrial animals (Makkar et al., Citation2014). Regarding fish, some trials have been carried out with various fish species to evaluate the use of diets containing different insect meals, often used as FM substitutes (Fasakin et al., Citation2003; St-Hilaire et al., Citation2007b; Sealey et al., Citation2011; Alegbeleye et al., Citation2012; Kroeckel et al., Citation2012; Oso and Iwalaye, Citation2014; Roncarati et al., Citation2015). The results of these trials confirm the possibility of insect meals inclusion in aquaculture feeds, even though there could be some limits related to both insect and fish species (Henry et al., Citation2015).
Tenebrio molitor (TM) belongs to the family of Tenebrionidae. It is currently mainly sold in the larvae stage for pet feeding and for fishing, but also as edible insects for humans (van Huis, Citation2013). TM is considered one of the most promising insect species suitable for mass production because it is easy to be bred and fed. Some studies have been performed using TM to feed poultry (Ramos-Elorduy et al., Citation2002; Bovera et al., Citation2015) and fish. In African catfish (Clarias gariepinus) Ng et al. (Citation2001) demonstrated that an inclusion up to 35% of TM meal (up to 80% replacement of the dietary fish meal component in the experimental diets) still maintained growth performances similar to those achieved using fishmeal diets. Nevertheless when fish have different nutritional requirements (i.e., for juveniles), the results may change, as noted by Roncarati et al. (Citation2015) who observed a reduction of weight growth and an increase of mortality in common catfish (Ameiurus melas) fingerlings fed TM larvae meal containing diets. In European sea bass (Dicentrarchus labrax) juveniles, data showed that an inclusion of 25% TM larvae meal did not affect growth performances while a higher inclusion level (50%) compromised the weight gain (Henry et al., Citation2015). Similar results were obtained in gilthead sea bream (Sparus aurata) juveniles (Henry et al., Citation2015) as, when the inclusion switched from 25 to 50%, weight gain, specific growth rate, feed conversion efficiency and protein efficiency ratio were compromised. To the author knowledge, no trials have been performed using TM in rainbow trout (Oncorhyncus mykiss) diets. The aim of this research was therefore to evaluate the effects of dietary inclusion of TM larvae meal on performance, nutrient digestibility and dorsal muscle proximate and FA composition of rainbow trout.
Materials and methods
Experimental diets
A commercial full-fat TM larvae meal purchased from Gaobeidian Shannong Biology CO. LTD (Shannong, China) was been used in this trial. Two diets, with different levels of TM inclusion (25% - TM25; 50% - TM50, as fed basis), were compared to a control diet (TM0). The three experimental diets were formulated to be nearly isoenergetic and isonitrogenous. Hence, with the increase of TM inclusion and the decrease of FM in the diets, some other dietary ingredients were also modified; in particular as cod liver oil has a high fat content, it was dramatically decreased in TM diets (80, 39 and 0 g kg–1 in TM0, TM25 and TM50, respectively). The grounded ingredients and the FO were thoroughly mixed; water was then added to the mixture to attain an appropriate consistency for pelleting, which was performed using a 3.5 mm die meat grinder. After pelleting, the diets were dried at 50°C for 48 h and stored in a fresh, dry and dark room until utilisation. The ingredients of the experimental diets are reported in .
Table 1. Tenebrio molitor proximate composition, and diets ingredients and proximate composition.
Fish and rearing conditions
A 90-day trial was carried out using and three hundred sixty mixed-sex rainbow trout. Fish were individually weighed (115.6±14.0 g) and randomly divided into twelve fiberglass tanks (W 0.5m; L 0.5m; H 0.4m). Artesian well water (constant temperature of 13±1°C) was supplied in open system (flow-throughout) with each tank having a water inflow of 8 L min–1. Dissolved oxygen (DO) was measured every fortnight and ranged between 7.6 and 8.7 mg L–1. Fish were fed to visual satiety twice a day per 6 days per week. To check growing rate, the biomass tanks were weighed in bulk every fortnight. Mortality was recorded daily.
Growth performance and somatic indexes
At the end of the trial, all fish were individually weighed and individual weight gain (WG) was calculated:
The following performance indexes were calculated for each treatment:
Two fish per tank (eight fish per treatment) were killed by over anaesthesia (MS-222) and dissected. Liver and gut were weighed to determine hepatosomatic (HSI) and viscerosomatic (VS I) indexes as follows:
Digestibility trial
An in vivo digestibility trial was performed in order to determine the apparent digestibility of diets nutrients. Forty-eight trout (mean weight 110±12 g) were divided in twelve 40-L cylindroconical tanks; DO (7.6÷8.7 mg L–1) and temperature (13±1°C) were checked weekly. After 14 days of acclimatization with the experimental diets, fish were fed by hand to visual satiety twice a day. The apparent digestibility coefficients were measured using the indirect acid-insoluble ash (AIA) method; 1% celite® (Fluka, St. Gallen, Switzerland) was added to the diets as an inert marker. The faeces were collected daily from each tank for three consecutive weeks, using a continuous automatic device, as described by Palmegiano et al. (Citation2006). The faeces were frozen (-20°C) until analyzed. The apparent digestibility coefficients of dry matter (ADCDM), organic matter (ADCOM), crude protein (ADCCP), and ether extract (ADCEE) were calculated following Palmegiano et al. (Citation2006).
Chemical analyses of feeds
Feeds were ground using a cutting mill (MLI 204; Bühler AG, Uzwil, Switzerland) and analyzed for dry matter (DM; AOAC# 934.01), crude protein (CP; AOAC# 984.13) and ash (AOAC# 942.05) contents according to AOAC (Citation2000); ether extract (EE; AOAC# Citation2003.05) was analyzed according to AOAC (Citation2003). The gross energy content was determined using an adiabatic calorimetric bomb (IKA C7000; IKA, Staufen, Germany). The proximate composition and energy level of the TM and of the experimental diets are shown in .
The FA composition of TM and of the experimental diets was assessed using the method described by Schmid et al. (Citation2009). Fatty acid methyl esters (FAME) were separated, identified and quantified on the basis of the chromatographic conditions reported by Renna et al. (Citation2014). Tridecanoic acid (C13:0) was used as internal standard. The results were expressed in absolute values as g 100 g-1 DM ().
Table 2. Fatty acid profile (g 100 g-1 dry matter) of Tenebrio molitor larvae meal and experimental diets.
All analyses were performed in duplicate.
Chemical analyses of fish dorsal muscle
At the end of the trial, the dorsal muscle of eight fish per treatment was collected, freeze-dried (Edwards MF 1000, Milan, Italy) and ground (cutting mill MLI 204; Bühler AG). Dry matter, crude protein, ether extract and ash contents of the fillets were determined according to the same procedures used for feed analyses (AOAC, Citation2000, Citation2003).
The freeze-dried and ground samples of fish muscles were also used to assess their FA composition, as reported by Schmid et al. (Citation2009). FAME were separated and quantified using the same analytical instruments and temperature programme previously described for the analysis of feed. The results were expressed as percentage of total detected FA. All analyses were performed in duplicate.
The atherogenicity (AI) and thrombogenicity (TI) indexes of fish muscles were calculated as reported in Palmegiano et al. (Citation2006):
where MUFA stands for monounsaturated fatty acids.
Statistical analysis
Data were analyzed by one-way ANOVA using IBM SPSS Statistics 20.0. Differences were evaluated by Turkey’s post-hoc test. Significance was declared at P≤0.05.
Results and discussion
The experimental diets were well accepted by the fish. The productive traits of the fish are summarized in . No significant differences were observed for individual FBW and growth WG. The trout of TM0 group showed significantly higher feed intake than those of TM50 group (FR: 1.40 vs 1.31%; P= 0.05); intermediate values were observed for TM25. Consequently, the TM0 group showed less favorable performance traits. In fact, FCR was significantly higher (1.20 vs 1.00 and 1.00 for TM0, TM25 and TM50, respectively), while PER (1.69 vs 2.06 and 2.04) and SGR (1.13 vs 1.30 and 1.27% day–1) were significantly lower (P= 0.01) in TM0 than TM25 and TM50. The survival rate observed in TM0 was significantly lower than that of TM25 and TM50 (P= 0.02), even if no specific pathological symptoms of disease were experienced. Moreover the TM0 group showed a significantly higher value of HSI than TM25 and TM50 (P≤0.01), while no significant difference was observed for VS I among groups.
Table 3. Growth performances, survival rate and somatic indexes of rainbow trout fed the experimental diets.
Such results indicate that the inclusion of 25 or 50% of TM in rainbow trout diets does not affect growth WG, but significantly ameliorates performance parameters. The effects on FCR, PER and SGR can be explained by the observed decreasing trend of voluntary intake for the TM diets, set at about -3.6% (TM25) and -6.4% (TM50) compared with the control diet.
Literature shows different responses to the use of insects in fish diets. Indeed, Ng et al. (Citation2001) observed a decrease in growth performances when insect meal exceeded the level of 40% of FM substitution in African catfish fingerlings. Similar results were also observed by Roncarati et al. (Citation2015) in fingerlings of common catfish. Moreover, some studies reported that the use of insects decreased growth performances and diet digestibility (St-Hilaire et al., Citation2007b; Kroeckel et al., Citation2012), while no differences were observed in other trials (Fasakin et al., Citation2003).
Our results confirm that the productive traits are not negatively affected by dietary inclusion of TM and that the latter seems to be able to reduce the fish voluntary intake, possibly due to the high quantity of fat and the type of fatty acids composing the fat. As reported in , the HSI decreased with the increasing dietary level of TM. This trend is similar to those observed in other studies, where FM was totally or partially substituted by insect meal or vegetable proteins (Sealey et al., Citation2011).
Among the considered apparent digestibility coefficients, only that of ADCCP was significantly lower for TM50 than TM25 and TM0 groups (90.1 vs 91.5 and 92.2%, respectively; P=0.05). No significant differences were observed for ADCDM, ADCOM and ADCEE among groups. Similarly to the results of St-Hilaire et al. (Citation2007b), our results showed an absolute high digestibility rate for lipids and protein. This occurred without significant differences for lipids apparent digestibility, but with a significant decrease in the protein apparent digestibility following increasing TM inclusion in fish diets. Nevertheless, even if protein digestibility decreased, the productive performances were not compromised and PER was improved. The reduction of ADCCP could be an effect of increasing quantity of chitin that reduces the apparent digestibility of dietary protein, mainly affecting Kjeldahl method to estimate protein content. Indeed, it has been shown that about 5-6% of nitrogen in TM is bound to chitin, and this leads to a protein overestimation of 1.1-1.3% on a fresh weight basis (Yi et al., Citation2013). The improvement of PER could instead be due to the increasing quantity of cysteine in the TM diets. It has to be mentioned that some studies showed how chitin could also interfere with lipid digestibility (Olsen et al., Citation2006; Kroeckel et al., Citation2012), but in the present study no differences were found for ADCEE.
The proximate composition of the trout dorsal muscle showed significant differences in DM, CP and EE contents, while the ash content remained unaffected by treatment (). The dietary inclusion of TM significantly decreased the DM and EE contents (P=0.01), contemporarily increasing the CP content (P=0.02). Similarly, a study conducted using black soldier fly (Hermetia illucens) showed a decrease in DM and EE in fish fillets with the inclusion of insect meal (Sealey et al., Citation2011).
Table 4. Proximate composition of the dorsal muscle of rainbow trout fed the experimental diets.
As reported in , the sum of octadecenoic acids (Σ C18:1=Σ Z18:1 t + C18:1 c 9 + C18:1 c 11), thanks to the high amount of oleic acid (C18:1 c 9), as well as linoleic acid (C18:2 n6) were the most represented FA in TM (7.58 and 6.97 g 100 g–1 DM, respectively). The Σ C18:1 and C18:2 n6 increased in the experimental diets with the increase of TM inclusion (for C18:1 c 9: 2.17, 3.24 and 4.24 g 100 g–1 DM, for TM0, TM25 and TM50 respectively). Therefore, the concentration of total MUFA and total PUFA increased, while the Σ n3/Σ n6 FA ratio decreased in the diets following the increase of TM inclusion. Very long chain n3 PUFA, such as eicosapentaenoic (EPA, C20:5 n3), docosapentaenoic (DPA, C22:5 n3) and docosahexaenoic (DHA, C22:6 n3) acids, were not detected in TM.
The FA composition of trout dorsal muscle was significantly altered by diet, showing significant differences for all individual FA and groups of FA except for C16:0 and total MUFA percentages (). The greatest differences were recorded for Σ C18:1 (Σ C18:1 t + C18:1 c 9 + C18:1 c 11) and C18:2 n6 that increased with the dietary inclusion of TM. Conversely, EPA, DPA and DHA significantly decreased as a consequence of both increase of TM and reduction of FM and FO in the diets. The atherogenicity and thrombogenicity indexes showed significant differences among treatments with opposite trends (a decrease for AI and an increase for TI) at the increase of TM inclusion in fish diets.
Table 5. Fatty acid composition (% of total fatty acids) of the dorsal muscle of rainbow trout fed the experimental diets.
It is well known that the FA profile of diets significantly affects the FA profile of fish tissues. In particular, in the current trial linoleic acid was increased in the dorsal muscles of trout fed diets containing TM, with the highest value recorded in the TM50 group, where cod liver oil was absent. In the same way, a reduction of EPA, DPA and DHA was recorded in fish fed TM. Even though the three experimental diets contained the same concentration of alinolenic acid (ALA), a reduced amount of ALA was observed in the dorsal muscle of trout belonging to both the TM25 and TM50 groups (-26.5% and -51.0% if compared to control diet, respectively).
The data reported in the present trial differ from what described by Sealey et al (Citation2011) who found increasing levels of ALA in dorsal trout muscles even if fish were fed diets containing similar ALA content. St-Hilaire et al. (Citation2007b) found that fatty acids were affected by diets with proportionally less ALA, EPA, and DHA in fish fed the hermetia illucens diets. These results are in agreement with those reported in the present study, as a decreasing of EPA and DHA in diets led to a consistent reduction of the same FA in fillets.
In fish fed increasing level of FM substitution, fillets showed consistent increase and decrease of Σ n6 and Σ n3 FA, respectively. This led to a significant reduction of the Σ n3/Σ n6 FA ratio, which ranged from 2.31 (TM0) to 0.41 (TM50) (P≤0.01), thus negatively affecting the nutritional value of the fillets. Palmegiano et al. (Citation2006) reported a similar trend for the Σ n3/Σ n6 FA ratio in muscle of rainbow trout fed diets containing increasing levels of a plant concentrate protein source. As far as the health indices are concerned, AI improved with increasing levels of TM inclusion, due to increasing percentage of Σ n6 PUFA, while TI worsened, due to the lower Σ n3 PUFA percentage. Nevertheless, the values are lower than those registered for other food products derived from terrestrial animals (Palmegiano et al., Citation2006).
Evidence from the present study indicates that FM can be partially substituted in trout diets using different inclusion levels of TM, without modifying growth performance. The inclusion of TM in the trout diets significantly decreased the relative fat quantity but also led to modifications of the dorsal muscle lipid profile. To balance the negative effects of diets poor in Σ n3 PUFA, and overcome the worsening of fillets FA profile, a finishing feeding strategy (i.e., period of starvation, followed by a short Σ n3 rich diet period at the end of the rearing period), might be applied, as already reported in previous trials (Zoccarato et al., Citation1994; Gause and Trushenski, Citation2013). Another solution would be to increase the Σ n3 FA concentration of insect meals by means of a modification of the insect rearing substrate, as already shown (St-Hilaire et al., Citation2007a).
Conclusions
T. molitor meal is an innovative raw material and seems to be promising to be used as alternative feedstuffs to FM in trout diets. Further research on specific feeding strategies and diet formulations is still needed to limit the negative effects of TM on the nutritional value of the lipid fraction of trout fillets.
Acknowledgements
This research was supported by the University of Turin (ex 60%) grant (Es. fin. 2014). The authors would like to thank Mr. Dario Sola, Dr. Paolo Montersino and Mr. Mario Colombano for fish care.
References
- AlegbeleyeW.O. Obasa S.O. Olude O.O. Otubu K. Jimoh W., 2012. Preliminary evaluation of the nutritive value of the variegated grasshopper (Zonocerus variegatus L.) for African catfish Clarias gariepinus (Burchell. 1822) fingerlings. Aquac. Res. 43:412–420.
- AOAC, 2000. Official methods of analysis of AOAC International, 16th ed. Association of Official Analytical Chemists, Gaithersburg, MA, USA.
- AOAC, 2003. Official methods of analysis of AOAC International, 17th ed. Association of Official Analytical Chemists, Gaithersburg, MA, USA.
- BoveraF. Piccolo G. Gasco L. Marono S. Loponte R. Vassalotti G. Mastellone V. Lombardi P. Attia Y.A. Nizza A., 2015. Yellow mealworms larvae (Tenebrio molitor, L.) as a possible alternative to soybean meal in broiler diets. Brit. Poultry Sci. 56:569–575.
- De Francesco M. Parisi G. Médale F. Lupi P. Kaushik S.J. Poli B.M., 2004. Effect of long-term feeding with a plant protein mixture based diet on growth and body/fillet quality traits of large rainbow trout (Oncorhynchus mykiss). Aquaculture 236:413–429.
- FAO, 2014. The state of world fisheries and aquaculture 2014. Food and Agriculture Organization, Rome, Italy.
- FasakinE.A. Balogun A.M. Ajayi O.O., 2003. Evaluation of full-fat and defatted maggot meals in the feeding of clarid catfish Clarias gariepinus fingerlings. Aquac. Res. 34:733–738.
- GaiF. Gasco L. Daprà F. Palmegiano G.B. Sicuro B., 2012. Enzymatic and histological evaluations of gut and liver in rainbow trout, Oncorhynchus mykiss, fed with rice protein concentrate based diets. J. World Aquacult. Soc. 43:218–229.
- GatlinD.M. Barrows F.T. Brown P. Dabrowski K. Gaylord T.G. Hardy R.W. Herman E. Hu G. Krogdahl A. Nelson R. Overturf K. Rust M. Sealey W. Skonberg D. Souza E.J. Stone D. Wilson R. Wurtele E., 2007. Expanding the utilization of sustainable plant products in aquafeeds: a review. Aquac. Res. 38:551–579.
- GauseB.R. Trushenski J.T., 2013. Sparing fish oil with beef tallow in feeds for rainbow trout: effects of inclusion rates and finishing on production performance and tissue fatty acid composition. N. Am. J. Aquacult. 75:495–511.
- HenryM. Gasco L. Piccolo G. Fountoulaki E., 2015. Review on the use of insects in the diet of farmed fish: past and future. Anim. Feed Sci. Tech. 203:1–22.
- KroeckelS. Harjes A.G.E. Roth I. Katz H. Wuertz S. Susenbeth A. Schulz C., 2012. When a turbot catches a fly: evaluation of a pre-pupae meal of the Black Soldier Fly (Hermetia illucens) as fishmeal substitute. Growth performance and chitin degradation in juvenile turbot (Psetta maxima). Aquaculture 364-365:345–352.
- MakkarH.P.S. Tran G. Heuzé V. Ankers P., 2014. State of the art on use of insects as animal feed. Anim. Feed Sci. Tech. 197:1–33.
- NgW.K. Liew F.L. Ang L.P. Wong K.W., 2001. Potential of mealworm (Tenebrio molitor) as an alternative protein source in practical diets for African catfish, Clarias gariepinus. Aquac. Res. 32:273–280.
- OlsenR. Suontama J. Langmyhr E. Mundheim H. Ringo E. Melle E. Malde M. Hmere G., 2006. The replacement of fish meal with Antarctic krill, Euphausia superba in diets for Atlantic salmon, Salmo salar. Aquac. Nutr. 12:280–290.
- OsoJ.A. Iwalaye O.A., 2014. Growth performance and nutrient utilization efficiency of Clarias gariepinus juveniles fed Bombyx mori (mulberry silkworm) meal as a partial replacement for fishmeal. Brit. J. Appl. Sci. Tec. 4:3805–3812.
- PalmegianoG.B. Agradi E. Forneris G. Gai F. Gasco L. Rigamonti E. Sicuro B. Zoccarato I., 2005. Spirulina as nutrient source in diets for growing sturgeon (Acipenser baeri). Aquac. Res. 36:188–195.
- PalmegianoG.B. Daprà F. Forneris G. Gai F. Gasco L. Guo K. Peiretti P.G. Sicuro B. Zoccarato I., 2006. Rice protein concentrate meal as a potential ingredient in practical diets for rainbow trout (Oncorhynchus mykiss). Aquaculture 258:357–367.
- Ramos-ElorduyJ. Gonzalez E.A. Hernandez A.R. Pino J.M., 2002. Use of Tenebrio molitor (Coleoptera: Tenebrionidae) to recycle organic wastes and as feed for broiler chickens. J. Econ. Entomol. 95:214–220.
- RennaM. Gasmi-Boubaker A. Lussiana C. Battaglini L.M. Belfayez K. Fortina R., 2014. Fatty acid composition of the seed oils of selected Vicia L. taxa from Tunisia. Ital. J. Anim. Sci. 13:308–316.
- RoncaratiA. Gasco L. Parisi G. Terova G., 2015. Growth performance of common catfish (Ameiurus melas Raf.) fingerlings fed insect meal diets. J Insects Food Feed 1:233–240.
- SchmidA. Collomb M. Hadom R., 2009. Fatty acid composition of Swiss cooked sausages. Fleischwirtschaft 89:101–104.
- SealeyW.M. Gaylord T.G. Barrows F.T. Tomberlin J.K. McGuire M.A. Ross C. St-Hilaire S., 2011. Sensory analysis of rainbow trout, Oncorhynchus mykiss, fed enriched black soldier fly prepupae, Hermetia illucens. J. World Aquacult. Soc. 42:34–45.
- ShepherdC.J. Jackson A.J., 2013. Global fishmeal and fish-oil supply: inputs, outputs and markets. J. Fish Biol. 83:1046–1066.
- St-HilaireS. Sheppard C. Tomberlin J.K. Irving S. Newton L. McGuire M.A. Mosley E.E. Hardy R.W. Sealey W., 2007a. Fish offal recycling by the black soldier fly produces a foodstuff high in omega-3 fatty acids. J. World Aquacult. Soc. 38:309–313.
- St-HilaireS. Sheppard C. Tomberlin J.K. Irving S. Newton L. McGuire M.A. Mosley E.E. Hardy R.W. Sealey W., 2007b. Fly prepupae as a feedstuff for rainbow trout, Oncorhynchus mykiss. J. World Aquacult. Soc. 38:59–67.
- van Huis A., 2013. Potential of insects as food and feed in assuring food security. Annu. Rev. Entomol. 58:563–583.
- YiL. Lakemond C.M.M. Sagis L.M.C. Eisner-Schadler V. Huis A.V. BoekelM.A.J.S.V., 2013. Extraction and characterisation of protein fractions from five insect species. Food Chem. 141:3341–3348.
- ZoccaratoI. Benatti G. Bianchini M.L. Boccignogne M. Conti A. Napolitano R. Palmegiano G.B., 1994. Differences in performances, flesh composition and water output quality in relation to density and feeding levels in rainbow trout Oncorhynchus mykiss (Walbaum) farming. Aquac. Fish. Manag. 25:639–647.