Potential of pre-pupae meal of the Black Soldier Fly (Hermetia illucens) as fish meal substitute: effects on growth performance and digestibility in European sea bass (Dicentrarchus labrax)

Potential of pre-pupae meal of the Black Soldier Fly (Hermetia illucens) as fish meal substitute: effect on growth performance and digestibility in European sea bass (Dicentrarchus labrax) MASTER THESIS STUDENT: Antonio Sánchez López ACADEMIC DIRECTOR: Silvia Martínez Llorens UNDER SUPERVISIÓN OF: Aires Oliva-Teles Helena Peres SEPTEMBER, 2015 D./Dña.: Antonio Sánchez López con D.N.I. nº 48509514F y como autor del Trabajo Fin de Master titulado: Potential of pre-pupae meal of the Black Soldier Fly (Hermetia illucens) as fish meal substitute: effect on growth performance and digestibility in European sea bass (Dicentrarchus labrax). Directora Académica El/La alumno/a Fdo: Silvia Martínez Llorens Fdo: Antonio Sánchez López Valencia a, ........... de .................................. de 2015 ABSTRACT In the present study a 62-day feeding trial was carried out in recirculating aquaculture system (RAS) by replacing fish meal protein subsequently by Hermetia illucens meal (HM), in practical diets for European sea bass (Dicentrarchus labrax L. 1758) to examine the effect on growth and nutrient digestibility. A control diet without insect meal and three experimental diets were formulated with an inclusion level of 6.5 %, 13% and 19.5% of HM. The diets were fed to triplicate groups of sea bass with an initial weight of 49.50 ± 0.5 g twice a day, six days per week, by hand until apparent satiation. The different replacing level of fish meal to insect meal in the three experimental diets did not affect to growth parameters (WG, FI, FCR, FE, SGR and DGI). The apparent digestibility coefficients (ADC) between groups were not affected by the inclusion of insect meal in diets until 19.5%. In general, our study shows that the incorporation of HM protein in European sea bass diets is possible as an alternative protein resource instead of the fish meal, more expensive and less sustainable. Further researches on HM meal processing to increase nutrient utilization are needed. Key words: European sea bass, Dicentrarchus labrax, fish meal, replacement, insect meal, Hermetia illucens, growth, digestibility. RESUMEN En el presente trabajo se llevó a cabo un ensayo de nutrición durante 62 días en un sistema de recirculación acuícola (RAS), en dietas para lubina (Dicentrarchus labrax L. 1758) con sustitución proteíca de harina de pescado por harina de insecto (HM), de la especie Hermetia illucens, para examinar los efectos sobre el crecimiento y digestibilidad de nutrientes. Se formularon una dieta control sin harina de insecto y otras tres dietas experimentales con un nivel de inclusión de 6,5%, 13% y 19% de harina de insecto. Cada grupo por triplicado, con un peso inicial medio por pez de 49, 50 ± 0,5 g, fueron alimentados a mano dos veces al día, seis días por semana, hasta saciedad. El nivel de sustitución de harina de pescado por harina de insecto en las tres dietas experimentales no afectó a los parámetros de crecimiento (WG, FI, FCR, FE, SGR y DGI). Los coeficientes de digestibilidad aparente (ADC) entre los diferentes grupos tampoco fueron afectados por la inclusión de harina de insecto en dietas hasta 19,5%. En general, nuestro estudio demuestra que la incorporación en dietas para lubinas de harina de insecto es posible como fuente de proteína alternativa al uso de harina de pescado, menos sostenible. Se deben llevar a cabo más investigaciones sobre el adecuado procesamiento de la harina de insecto para poder aumentar los niveles de utilización de nutrientes. Palabras clave: lubina, Dicentrarchus labrax, harina de pescado, sustitución, harina de insecto, Hermetia illucens, crecimiento, digestibilidad. MAIN OBJECTIVES  Evaluation of the potential of insect meal inclusion in different levels in diets for European sea bass juveniles on: Growth performance, voluntary feed intake, feed utilization (including protein, lipid and energy budgets).  To measure the digestibility coefficients for juvenile of European sea bass fed diets with different levels of fish meal substitution by insect meal, in order to adequate the optimum level of fish meal replacement. 1. INTRODUCTION The global population is increasing and in order to maintain at least the current level of per capita consumption, the world will require an additional 23 millions tonnes of aquatic food by 2030, which must come from aquaculture. Although the discussion on the availability and use of aquafeed ingredients often focused on fishmeal and fish oil resources (including trash fish), considering the past trends and future predictions, sustainability of the aquaculture sector is more likely to be closely linked with the sustained supply of terrestrial animal and plant proteins, oils and carbohydrate sources for aquafeeds. On these grounds, the tremendous challenge of feeding our planet while safeguarding its natural resources for future generations has gained increasing importance in recent decades (FAO, 2014). Intensive aquaculture production of fish, particularly carnivorous fish, is still base on high quality fish meal and fish oil. The steady decline in catches of wild fish and the increased demands for livestock and aquaculture feeds have resulted in a rapid decrease in the availability of fish meal (FM) and fish oil (FO) and in their concurrent price increase (FAO, 2014). Nevertheless, the use of these commodities aquafeeds has been decreasing (Karapanagiotidis, 2014), due to a higher demand of fisheries products, world limited availability, market supply fluctuations and raising prices, which have stimulated research on the use of more sustainable alternative feedstuffs (Gatlin et al., 2007). For carnivorous fish diets protein is the largest component, the optimal dietary levels vary with species. It is known that European sea bass juveniles have a high dietary protein requirement, ranquing from 45% to 50% (Peres and Oliva-Teles, 2006). For this reason a search of a sustainable ingredient for substituting the abusive use of fish meal, is nowadays a challenge for the nutrition area in aquaculture, because the cost of aquaculture feeds represents 40-70% of the cost of the fish produced (Rana et al., 2009; Wilson, 2002) and is a limited resource. So, development and use of alternatives to fish meal and fish oil in aquaculture diets continue a high priority (Glencross et al., 2007) in order to aquaculture production would allow to remain economically and environmentally sustainable over the long term (Barroso et al., 2014). In the last decade, the use of vegetable protein rich ingredients in practical diets of carnivorous fish species, has focused much attention in order to wider the amount and diversity of plant ingredients of aqua feeds (Messina et al., 2013). Soya and other terrestrial plants rich in proteins and lipids have been introduced into diet of aquaculture fish to replace FM and FO (Hardy, 2002; Espe et al., 2006; Gatlin et al., 2007). However, the presence of anti-nutritional factors in plant meals (Tacon, 1993; Francis et al., 2001; Ogunji, 2004; Collins, 2014), the potential problems of the inflammation of the digestive tract (Merrifield et al., 2011) and the decreased palatability of the meal (Papatyphon and Soares, 2001) are of concern. Also, plant feedstuffs have lower protein contents and essential amino acids (EAA) imbalances, and they are often deficient in Lys and Met. Such deficiencies can primarily lead to an increase in feed intake (FI), because the fish eat more to cover its basics needs. In this context, insects are part of the natural diet of both freshwater and marine fish (Howe et al., 2014; Whitley and Bollens, 2014), and in general, edible insects were found to be good sources of proteins, fat, energy, vitamins and minerals (Rumpold, 2013). In comparison to conventional livestock in general, insects have a higher feed conversion efficiency, need less amount of feed for the production of 1 kg biomass, have a higher fecundity (Nakagaki and Defoliart, 1991) and leave a small ecological footprint (no needs for arable land, low need for energy and water) (Oonincx and de Boer, 2012). It has to be investigated more in detail whether insects have the potential to replace or at least decrease the amount of fish meal and fish oil in fish feed considering the lack of polyunsaturated omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the fatty acid profiles of insects. Nowadays the studies of the replacement of fishmeal with insects in the diet of fish have emerged and the promising results have encouraged further research. In general, the AA patterns of insects are taxon-dependent (Barroso et al., 2014), most of insects tested in fish diets, show a good correlation with fish requirement values (Hasan, 2001; NRC, 2011; The experimental design system consisted of a thermo-regulated recirculation water system equipped with twelve fiberglass tanks of 60 litres water capacity, each one with a faces settling column connected to the outlet designed according Cho et al (1982), provided with a thermostatic control and regulation of water temperature. The effluent of each tank flowed into a common drainage channel which led to the biological filter composed of two square tanks of 500 l capacity full filled with bio-balls and mechanical sand-filter. During the trial, the system ensured nearly constant and optimal water quality to fishes: water-flow was established at about 4´5 L/min per each tank, constant water temperature 26ºC, salinity 36 g l-1 and dissolved oxygen was kept above 80% of saturation. The experimental fish were subjected to a 12h light/12h dark artificial photoperiod regime. One hundred and twenty European sea bass were used. Ten fishes with an average weight per fish of 49.4 ± 0.5 g were established in each tank with an initial density of 0.499 kg m-3. The diets were randomly assigned to triplicate groups of fish like the next Table 4 show. Table 4. Assignation of tank for each experimental diet. DIET TANK TANK TANK HM 0 2 4 9 HM 6.5 3 6 8 HM 13 10 11 12 HM 19.5 1 5 7 After one week to acclimate to the experimental conditions the fishes were hand-fed until they start to refused the pellets, twice a day with the correspondent experimental diets per each tank during morning and afternoon, with minimum 6 hour between each fed, 6 days per week, over a period of 62 days. Thirty minutes after the afternoon fed, each tank and settling columns where thoroughly cleaned to remove excess of feed and faeces, with a partial water renovation from the filter cleaning. During this period the actual feed intake per tank was recorded every 15 days. The first 7 days were used for adaptation to the feed and no faeces were collected, after that, faeces accumulated in each settling column were daily collected before the morning meal during 20 days and centrifuged at 5000 rpm for 10 minutes, discarded the supernatant, and stored at -20ºC until analysis. 2.3. Chemical analysis Chemical analysis of ingredients, diets and faeces were conducted as follows: dry matter, by drying the samples at 105°C until constant weight; ash, by incineration in a muffle furnace at 450°C for 16 hours; protein (N x 6.25) by the Kjeldahl method following acid digestion, using Kjeltec digestion and distillation units (Tecator Systems, Höganäs, Sweden; models 1015 and 1026, respectively); lipids in ingredients and diets by extraction with petroleum ether using a Soxtec system (Tecator Systems, Höganäs, Sweden; extraction unit model 1043 and service unit model 1046), and in faeces by a gravimetric method (Folch et al., 1957) due to the limited amount of faeces sample; gross energy, by direct combustion of samples in an adiabatic bomb calorimeter (PARR Instruments, Moline, IL, USA; PARR model 1261); chromic oxide by acid digestion according to Furukawa and Tsukahara (1966). 2.4 Tissue sampling A pooled sample of 10 fish at the beginning of the trial was stored at -20ºC for future whole body analysis. On day 62 of the experiment the total number of fish were individually body weighed from each tank to know the final weight per treatment. At the end of the growth trial 3 fish per tank were randomly sampled from each group 4 hours after the morning meal. Individual blood samples were withdrawn from caudal vessels using heparinized syringes. Plasma samples were obtained by centrifugation at 3000 rpm for 15 min using a high-speed microcentrifugation and kept at -70ºC for future analysis. Viscera with liver were dissected out from that three fish in each replicate tank, weighted and then, only liver was weighted to get viscerosomatic index (VSI) and hepatosomatic index (HSI) respectively. Another 3 fish from each tank were sampled for whole wet weight and length and stored at -20ºC for future composition analysis. 2.5 Evaluation of growth performance parameters At the end of the trial, following variables per tank were evaluated: Weight gain (% IBW) = (final weight − initial weight) × 100 / initial weight. Weight gain (g kg ABW-1 day-1) (WG) = ((FBW-IBW) x 1000) / (ABW x 62 days). Specific growth rate (SGR %, day−1) = {(Ln (final weight) − Ln (initial weight)) / duration (62 days)}×100. Survival (%) = 100 × (final number of fish/ initial number of fish). Feed intake (g kg ABW-1 day-1) (FI) = ((feed intake (g dry matter / fish) x 1000) / (ABW x 62 days) Daily growth index (DGI) = 100 x [(final weight)1/3 – (initial weight)1/3] x (day-1) Feed conversion ratio (FCR) = live weight gain (g) / dry feed intake (g). Food efficiency (FE) = Weight gain (g) / Total intake (g) Protein efficiency ratio (PER) = live weight gain (g) / dry protein intake (g). 2.6 Evaluation of Apparent digestibility coefficients (ADCs) Apparent digestibility coefficients (ADCs) of protein, lipids, dry matter, and energy of the diets were determinate by the following formulas: ADC Protein (%) = 100 x 100 [(Cr2O3 in diet/ Cr2O3 in faeces) x (Crude protein in faeces/Crude protein in diet)]. ADC Lipids (%) = 100 x 100 [(Cr2O3 in diet/ Cr2O3 in faces) x (Lipids in faeces/Lipids in diet)]. ADC Energy (%) = 100 x 100 [(Cr2O3 in diet/ Cr2O3 in faeces) x (Energy in faeces/Energy in diet)]. ADC DM (%) = 100 x (1Cr2O3 in diet/ Cr2O3 in faeces). 2.7. Statistical analysis Data of growth and digestibility were checked for normal distribution and homogeneity of variances. Means were then compared by one-way ANOVA followed by Tukey test at a significance level of 5%. All analyses were made using Statgraphics Centurion XVI (Statpoint technologies Inc.). 3. RESULTS 3.1. Evaluation of growth performance parameters After 62 days the results on growth and feed utilization of European sea bass fed with the experimental diets are presented in Table 4. During experiment no mortality of the fish was recorded. Growth performance results of fish in all the dietary treatments in the present experimental condition were satisfactory due to all fish accepted the experimental diets which were not strongly influenced by dietary formulation. The different levels of replacing of fish meal to insect meal in the three experimental diets did not affect final wt, WG, FI, FCR, FE, SGR and DGI in European sea bass (P>0.05). Just PER obtained in the control diet (HM0) showed higher level than the experimental diet with 19.5% of insect meal inclusion (HM19.5). Table 4. Growth performance, feed efficiency and survival of European sea bass feed experimental diets with increasing levels of insect meal. HM0 HM6.5 HM13 HM19.5 SEM* Initial wt1 (g) 50 50 50 50 0.13 Final wt2 (g) 123 131 132 127 2.47 Survival (%) 100 100 100 100 WG3 (g) 733 816. 825 778 24.86 WG (g/kg/day) 13 14 14 14 0.24 WG (% IBW) 146 163 165 155 5.03 FI4 (gDM/kg/day) 22.49 23.75 23.84 22.88 0.44 FCR5 1.65 1.64 1.64 1.62 0.02 FE6 0.61 0.61 0.61 0.62 0.008 SGR7(% / day). 1.46 1.56 1.57 1.51 0.04 DGI8 2.09 2.26 2.28 2.18 0.05 PER9 1.38 a 1.34 ab 1.29 ab 1.27 b 0,01 1In wt: initial weight. 2 Fn wt: final weight. 3 WG: percent weight gain. 4 FI: Feed Intake 5 FCR: Feed conversion ratio 6 FE: Feed efficiency ratio 7 SGR: Specific growth rate 8 DGI : Daily growth index 9 PER: Protein efficiency ratio * Standard error of the mean. Values are means of triplicate groups. Within a row, means with differentletters are significantly different (P>0.05). 3.2 Digestibility of the diets and raw material The apparent digestibility coefficients (ADC’s) of the four diet groups were high, with ADC’s of protein around 91-93%, lipids 89-92%, energy 78-83% and dry matter 6674% (Table 5). No significant differences (P<0.05) were found between the four groups in any of the ADC’s results. Table 5. Apparent digestibility coefficients (ADC) of the four experimental diets. Diet HM0 HM 6.5 HM 13 HM 19.5 SEM* ADC DM 66.16 74.48 71.35 69.84 3.64 ADC Protein 91.29 93.44 92.33 91.58 1.11 ADC Energy 78.28 83.69 81.93 81.39 2.64 ADC Lipids 89.51 91.46 92.64 92.30 1.82 * Standard error of the mean. Data shown as mean ± SD (n=3). Figures in the same row with different letters indicate a significant difference (P < 0,05). 4. DISCUSION The results obtained from the present study in growth parameters showed that the insect meal can be included successfully up to 19.5% without negative effects on growth and fish performance. Like in our study, Zhang et al., 2014 shown that in yellow catfish, 25% replacement of fishmeal by black soldier fly larva powder produced no significant difference in the growth index and immunity index when compared with those in control group without insect meal. The results that we obtain could be explained for the addition of Taurine in the four experimental diets. Taurine is an abundant non-proteic amino acid involved in numerous physiological processes (Divakaran, 2006), also is recognized as a potent antioxidant, having an oxygen free radical scavenger effect, leading to a reduction of lipid peroxidation, reduction of membrane permeability, and reduction of membrane permeability, and reduction of intracelular oxidation and so protecting tissue form oxidative injury (Hagar, 2004; Parvez et al., 2008; Yu and Kim, 2009; Zeng et al., 2010). The taurine appear to have beneficial proprieties on the performance and wellbeing of carnivorous fish (El-Sayed, 2013). In fish, under normal nutritional conditions, taurine is synthesized from methionine and cysteine metabolism, but the limited capacity to synthesize may impose the requirements for methionine and cysteine, such as during early life stage or when the dietary intake of this AA is insufficient (Buñuelos-Vargas et al., 2014). Apart from insect meal, the experimental diets of this trial have some partial plant feedstuffs, and some plant feedstuffs have negligible taurine levels, so fish meal replacement by these ingredients may compromise dietary levels (El-Sayed, 2013), but little information has been reported about the role of taurine on the metabolic pathway and antioxidant status of carnivorous fish, particularly its effects when supplemented in plant protein based diets (Buñuelos-Vargas et al., 2014). The increasing inclusion of insect meal in the experimental diets maybe could compromise the optimum levels of taurine, therefore we decided to supplement all diets with extra taurine. So in fact, this taurine extra supplementation may explain that no statistical differences were found for this growth trial between any experimental groups. Another experiment of Salze et al. (2010) also indicated that supplementation of methionine and lysine in addition to taurine is imperative for the complete replacement of fish meal with alternative protein sources from the diets of cobia. In this study amino acids were not added to the experimental diets so that maybe explain the significant results between the control diet (HM0) and experimental diet with an inclusion of 19.5% of insect meal (HM19.5), the decreasing levels of fish meal became deficient diets in certain amino acids such as methionine which compromise the correct use of the remaining amino acids, for that reason the lowest values of PER appeared in the experimental diet HM19.5. Also these results shown that the feed intake between groups was the same, so no negative effects (less palatability or imbalance of amino acid) of this fish meal substitution appear with the inclusion of insect and plant proteins. However, the amino acid and palatability issue could also be overcome with amino acid supplementation or appropriate feed formulation (Kader et al., 2010) or also by adding natural attractants. In this case all the diets, including the highest inclusion of insect meal (19.5%) instead of fish meal, were found effective for European sea bass. The results differ when vegetable proteins are used, in the studies carry out by Kaushik et al. (1995) in rainbow trout (Oncorhynchus mykiss) and Salze et al. (2001) in cobia (Rachycentron canadum), with substitution of fish meal by soybean shown a lower feed intake with higher inclusion levels of soybean protein in diets, something that also had detrimental effects on the performances of fish. Another factor that could affect feed intake is the presence of chitin in black soldier meal (Kroeckel et al., 2012). In this case, no evidence of that factor had been reported but there are several study that reported a reduce of growth and feed intake, for example in rainbow trout with levels of 10% chitin in diets (Lindsay et al., 1984). The palatability is an important factor to measure the feed intake on fish, in this case the inclusion of insect meals without any difference in the feed intake between groups showed no effect on the acceptability of the diet with less fish meal (HM6.5, HM13, HM19.5) but sometimes the fish meal substitution reduces the palatability so is important in that cases to correct that. Kader et al. (2010) investigate the effect of supplementation of small amount (10%) of crude ingredients such as fish soluble (FS), squid meal (SM) and krill meal (KM) in high soy protein concentrate based diets was effective to achieve similar performance of the red sea bream as with the control diets group diet based with fishmeal. Supplementation of FS, SM and KM acted as natural feeding attractants as well as being effective in balancing amino acids and masking the unpalatable substances in diet with soy protein concentrate (Abdul Kader et al., 2012). In other study from St-Hilaire et al (2007a) that they evaluated the use of black soldier fly in feed for rainbow trout (Oncorhynchus mykiss), the weight gain of fish was less for fish fed with 50% of insect meal substitution, but any significant different appear between the fish fed with diets of 25% of insect meal and the control diet without insect meal in weight gain and feed conversion ratio, the present study showed the same results for those parameters. Lock et al. in 2014, obtained an increased in feed conversion efficiency in diets with black soldier meal for Atlantic salmon (Salmo salar), and also any differences between any dietary groups (25%, 50% and 100%) and sensory testing of fillets were found. The method of preparation of insect meal might impact on the results. In juveniles of turbot (Psetta maxima L.), a marine carnivorous flatfish, Kroeckel et al. (2012) discovered that growth performance decreased, generally, as the percentage of insect meal in test diets increased, showed that higher specific growth rate and final body weight with the fish fed with the control diet, without insect meal, than those fish fed with any of the experimental diets containing insect meal. In terms of feed conversion, significantly higher values were obtained in the fish groups fed with higher percentage of insect meal (49%, 64% and 76%), being a negative result for the use of this alternative meal. Also like in our study the protein efficiency ratio (PER) were affected by dietary treatment and decreased significantly according increasing levels of insect meals. The authors of that study concluded that juveniles turbot could have some troubles in digesting chitin, and only a limited percentage of insect meal from black soldier fly can replace the fish meal in commercial diet for turbot. Carnivorous fish can potentially adapt to a plant-based diet after a few generations of artificial selection (Le Boucher et al., 2011, 2012) so is important to continue with research like this one in the feeding area preference of fish to study the fish are able to adapt after several generation of exposure of this insect meal diets against the commercial fish meal diets. In the specie used, European sea bass, there are some studies that suggest that almost total replacement of fish meal by vegetable ingredients in diet does not affect fish growth or feed utilisation (Kaushik et al., 2004). On the other hand, Gomez-Requeni et al. (2004) found that a total substitution of fish meal reduced growth performances by about 30%. Several experiments have shown that black soldier fly larvae inclusion in diets could partially or fully substitute for fishmeal in fish diets. However, additional trials as well as economic analyses are necessary because reduced performance has been observed in some cases, and the type of rearing substrate and the processing method affect the utilization of the larvae by fish. (Makkar et al., 2014). Digestibility is the main factor in evaluating the suitability of feed ingredients for a target fish species. Usually does not vary significantly with the amount of ingested food, the number of meals (Choubert et al., 1984), environmental factors such as temperature and salinity, or biotic factors, such as age (Cho and Kaushik, 1990). But according with species, extrusion process of feedstuffs and factors intrinsic to the feed and the ingredients that compose it, the digestibility coefficients could vary. Regarding to our results, in the present study we observed relatively high ADC values for lipids (8992%) and proteins (91-93%), suggesting a potential for these insect proteins as partial replacement for fish meal in European sea bass diets. On the other hand, lower and less homogeneous results for ADC of dry matter (66-74%) and energy (78-83%) were reported between diet groups , but not statistical differences appear. Chemical composition of insect meal is very variable and highly dependent on processing technology and the nutritional composition of insect diet (Makkar et al., 2014), so this will be affect to the digestibility coefficient parameters in fish. The nutritional value and nutrient content of insect meal may be greatly affected by quality of the species of insect. Accordingly to the insect specie used in this case, black soldier fly (Hermetia illucens), in a trial done by Kroeckel et al. (2012) in juveniles of turbot (Psetta máxima), the calculated ADC´s for Hermetia meal were lower than this trial for all the parameters: 45.2% for organic matter, 63.1% for crude protein, 78.0% for crude lipid, and 54.5% for gross energy. Lipids, particularly fatty acids, are the preferred source of digestible energy for fish (Tocher 2003; Lim et al., 2011). Insect meal used in this study had a lipid content of 5.47 % which was lower than the content in fish meal (11.3%). However, the ADC’s of lipids did not showed any significantly difference between the control diet with 100% of fish meal with the rest diet with increasing levels of substitution, so all lipid sources were effectively digested (>89 %). The results of lipids ADC were similar to the results obtained by Kroeckel et al. (2012) for turbot juveniles. In that study the results of control diet comparing to our control diet was higher, 98.7% due to 89.51% in the present study. But the results for 33% of insect meal comparing to ours with 19.5% of insect meal replacement were in both cases around 92 % of ADC for lipids. The digestibility of lipids can be related with functional changes in the intestinal level induced lipids, as it known that the inclusion of vegetables oils in the diet of carnivorous fish can adversely affect the process of digestion and absorption, this can immediately notice that the inclusion up to 22.5% non-affected the digestive process (Santigosa et al., 2011). Also a modifications of enterocyte membranes were also described in fish fed with vegetable oils (Sitjà-Bobadilla et al., 2005) and this can compromise the intestinal function, thus reducing lipid digestibility (Geurden et al., 2009). In plant protein-based diets reduced lipid digestibility was ascribed to the soybean meal (Øverland et al., 2009), maybe related to a result of physiological changes in secretion of bile acid (Yamamoto et al., 2007), caused by the alcohol-soluble substance of soybean meal (Yamamoto et al., 2008). In this study all diets were supplemented with taurine so that may explain that there was no statistical difference between the four different groups in de lipids ADC as taurine has been reported to increase the nutrient absorption, particularly the lipid fraction, through the strict dependence on taurine for bile acid conjugation and through the normalization of the intestinal morphology (Buñuelos-Vargas et al., 2014). In the present study, we observed relatively high ADC values of protein for all experimental diets, something that suggested the high potential for insect meal as partial replacement for fish meal in European sea bass diets, in concordance with the reported ADC’s of crude protein for fish meal in this specie, as around 90% (da Silva and OlivaTeles, 1998). In comparison to other studies done with alternative animal protein sources Davies et al. (2009) in turbot, very low result were reported for lipid and energy digestibility for poultry meat meal (ADC lipid: 54.6% and ADC energy: 45.2%), spray-dried haemoglobin meal (ADC lipid: 34.6% and ADC energy: 35.6%) and hydrolysed feather meal (ADC lipid: 37.1% and ADC energy: 21.7%) comparing to the results obtained in the present study (ADC lipid:89-92% and ADC energy:88-90%). That low results were a result of the short digestive tract and low metabolic rate of the specie selected. In other hand, an insect experiment done by Ogunji et al. (2009) for determinate the ADC’s of the use of horsefly maggot meal in diets for carp (Cyprinus carpio) was really successful with high values of ADC’s (ADC lipid: 96.8%, ADC protein: 84.9%, ADC energy: 74.9%) and also close to results of this study of European sea bass. In the same study they determinate also the ADC,s in Nile tilapia with lower results than for carp (ADC lipid: 86.1%, ADC protein: 57.7%, ADC energy: 58.1%).That results are maybe explained for the presence of chitin, it has been reported that a low lipid utilization and small lipid retention at high black soldier meal inclusion levels can be attributed to the presence of chitin and its negative influence on lipid digestibility (Kroeckel et al., 2012). In this study the ADC levels for lipids apparently no signs that the lipid utilization was affected by the presence of chitin in the diets. The relative low ADC’s of energy (78-83%) and dry matter (66-74%) of this trial using insect meal is most certainly related to the high fibre content, as it is known that fish, specially carnivorous species, poorly digest complex carbohydrates (Enes et al., 2011). Indeed, non-digestible carbohydrates, present in high quantity in a diet, may also impair digestibility of other nutrients by reducing gut-retention time of feed and time available for nutrients absorption (Stone, 2003; Fountoulaki et al., 2005; Enes et al., 2011). The results of ADC for dry matter were the lowest comparing to the rest of ADC’s, 6674%, but no significant differences between groups were found. The control diet and the other three experimental diets contain Soybean meal, wheat meal, wheat gluten and corn gluten so may be the low results are related to the presence in the vegetable feedstuff of effect on digestion and nutrient absorption in gilthead sea bream (Sparus aurata L.). Aquac Res. 42, 962-974. 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