Insect-based aquafeeds modulate the fatty acid profile of zebrafish: a comparison on the different life stages

Insects are considered as an alternative and sustainable ingredient for feed production. In this study, Hermetia illucens (Hi) prepupae (fed on coffee roasted by-product added with 10% Schyzochytrium sp., a marine protist rich in polyunsaturated fatty acids) was processed into meal and included at graded levels in five experimental diets to replace dietary fish meal (0, 25, 50, 75, 100%) offered to zebrafish (Danio rerio) as experimental model. The fatty acids (FAs) profile of fish larvae (20 days), juveniles (2 months, deprived of the viscera) and adults (6 months, male and female, deprived of the viscera) specimens was investigated to evaluate the impact of dietary FM replacement with full-fat Hi prepupae meal. For the first time, the quantification of FAs in Danio rerio, performed by gas chromatography-mass spectrometry, was computed in absolute terms (mg 100g-1 dw), identifying the real variation in the content of any single FA. In fish, quantified total FAs in larvae, juvenile, adult male and adult female were 134±2, 235±8, 266±3 and 266±8 mg g-1 dw, respectively. With respect to zebrafish fed the control diet, specimens fed diet with increasing level of Hi prepupae meal showed significantly higher content of saturated and omega6 FAs, and significantly lower content of poly-unsaturated and omega3 FAs, reflecting partially the FAs composition of the administered diets. At the same time, the docosahexaenoic/eicosapentaenoic acid ratio increased significantly. Moreover, adult female showed a higher content of PUFA with respect to adult male, which could be justified by the needs of physiological reproductive processes. The principal component analysis demonstrated that the FAs composition in Danio rerio depends on both the life stage and the diet

Application of laboratory methods for understanding fish responses to black soldier fly (Hermetia illucens) based diets

A major challenge for development of sustainable aquafeeds is its dependence on fish meal and fish oil. Replacement with more sustainable, nutritious and safe ingredients is now a priority. Over the last years, among several alternatives proposed, insects have received great attention as possible candidates. In particular, the black soldier fly (Hermetia illucens; BSF) represents a concrete example of how the circular economy concept can be applied to fish culture, providing a valuable biomass rich in fat and protein valorising organic by-products. In the last decade, several studies have been published about the use of different BSF dietary inclusion levels for various fish species including experimental models. Varying and encouraging results have been obtained in this research field using a plethora of laboratory methodological approaches that can be applied and coupled to obtain a comprehensive view of the BSF-based diets effects on fish physiology, health, and quality. The present review aims to explore some of the most promising laboratory approaches like histology, infrared spectroscopy, gut microbiome sequencing, molecular biology, fish fillets’ physico-chemical and sensory properties, essential for a better understanding of fish welfare and fillet quality, when BSF is used as aquafeed ingredient. In particular, great importance has been given to European finfish species and experimental models.publishedVersio

Evaluation of Growth Performance and Environmental Impact of Hermetia illucens Larvae Reared on Coffee Silverskins Enriched with Schizochytrium limacinum or Isochrysis galbana Microalgae

Hermetia illucens is a promising insect due to its ability to convert low-value substrates as food chain by-products into highly nutritious feed. Its feeding and nutrition are important issues. The aim of this work was to investigate the effect of different substrates consisting of coffee silverskin, a by-product of the roasting process, enriched with different inclusions of microalgae (5%, 10%, 20%, and 25%), Schizochytrium limacinum, and Isochrysis galbana, combined with the assessment of environmental sustainability by LCA. In general, the addition of microalgae led to an increase in larval growth performance due to the higher content of protein and lipids, although S. limacinum showed the best results with respect to larvae fed with coffee silverskin enriched with I. galbana. A higher prepupal weight was observed in larvae fed with 10%, 20%, and 25% S. limacinum; shorter development times in larvae fed with 25% of both S. limacinum and I. galbana; and a higher growth rate in larvae fed with 25% S. limacinum. The 10% S. limacinum inclusion was only slightly different from the higher inclusions. Furthermore, 10% of S. limacinum achieved the best waste reduction index. The greater the inclusion of microalgae, the greater the environmental impact of larval production. Therefore, the addition of 10% S. limacinum appears to be the best compromise for larval rearing, especially considering that a higher inclusion of microalgae did not yield additional benefits in terms of the nutritional value of H. illucens prepupae

Growth and Welfare Status of Giant Freshwater Prawn (Macrobrachium rosenbergii) Post-Larvae Reared in Aquaponic Systems and Fed Diets including Enriched Black Soldier Fly (Hermetia illucens) Prepupae Meal

Due to the limited application of insect meal in giant freshwater prawn (Macrobrachium rosenbergii) culture, the present study aimed to (i) produce spirulina-enriched full-fat black soldier fly (Hermetia illucens) prepupae meal (HM) and (ii) test, for the first time, two experimental diets characterized by 3% or 20% of fish meal and fish oil replacement with full-fat HM (HM3 and HM20, respectively) on M. rosenbergii post-larvae during a 60-day feeding trial conducted in aquaponic systems. The experimental diets did not negatively affect survival rates or growth. The use of spirulina-enriched HM resulted in a progressive increase in α-tocopherol and carotenoids in HM3 and HM20 diets that possibly played a crucial role in preserving prawn muscle-quality traits. The massive presence of lipid droplets in R cells in all the experimental groups reflected a proper nutrient provision and evidenced the necessity to store energy for molting. The increased number of B cells in the HM3 and HM20 groups could be related to the different compositions of the lipid fraction among the experimental diets instead of a nutrient absorption impairment caused by chitin. Finally, the expression of the immune response and stress markers confirmed that the experimental diets did not affect the welfare status of M. rosenbergii post-larvae

An experimental study on the effects of breeder diets on newborn seahorses (Hippocampus guttulatus)

Póster.-- VIII Congreso ibérico de Ictiología, realizado telemáticamente del 15 al 19 junio 2020Aquaculture represents a valid alternative to wild captured seahorses but ex-situ production still needs to face several biological and technical challenges (Cohen et al., 2016; Planas et al., 2017). Low spawning quality and juvenile survival rates are the most critical factors for optimizing commercial seahorse production. Reproduction represents a key aspect in breeding success, and broodstock nutrition is one of the most important factors in reproductive achievements. Even though the growth of adult Hippocampus guttulatus fed on Artemia may be satisfactory, mysidaceans have been considered an excellent prey for the on-growing and breeding of some seahorse species (e.g. H. abdominalis and H. hippocampus) (Olivotto et al., 2011). In this study, we assessed the effects of Artemia and mysidaceans in newborn. We addressed the following questions: (1) How experimental diets are reflected in general features and biochemical composition of H. guttulatus newborn?, (2) Do mixed diets perform better than monospecific diets?, and (3) Does H. guttulatus follow a mixed income-capital breeding strategy? The main objectives of the study were (1) to propose a breeder’s diet enhancing reproduction performance in the species, and (2) to ascertain when and how long the diet should be administered to take effectStudy funded by project CGL2015-68110-R (MINECO, Spain)N

A multidisciplinary experimental study on the effects of breeders diet on newborn seahorses (Hippocampus guttulatus)

17 pages, 7 figures, 4 tables.-- This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY)The global trade in seahorses is increasing and new rearing techniques are currently available for a few species. One of the main bottlenecks in seahorse production is reproductive success, which is dependent upon the administration of high quality diets to breeders. However, little is known about the most adequate diets, on how they should be administered and on how they might affect newborn performance. In this study, three homogeneous groups of adult seahorses Hippocampus guttulatus were maintained in captivity. Each group was fed on one of the following diets since the onset of the breeding period: unenriched adult Artemia (diet A), unenriched adult Artemia and mysidaceans (diet AM) and mysidaceans (diet M). As a positive control, a wild pregnant male was used. The mixed diet AM provided the highest overall breeding success and reasonable fatty acid profiles, and better resembled newborn from a wild male. The use of mysidaceans solely (Diet M) provided the worse results in spite of the high DHA content. Significant differences were observed in newborn characteristics and fatty acid profiles among dietary groups and along the breeding season, especially in total n-3 HUFA and DHA. Monospecific diets including Artemia or mysidaceans very likely suffered nutritional deficiencies, which were reflected in morphological alterations of the muscle tissue (diet A) or abnormal early mortalities in newborn (diet M). Three progressive stages were identified along the whole breeding period: initial mixed capital-income period (100–120 days since the onset of the breeding period), followed by an inflection period (short transitional stage – income sources), and finally a long period characterized by the use of income sources and the progressive exhaustion of body reserves. Special attention should be deserved to the progressive changes in fatty acid profiles along the breeding season, resulting in a decrease in newborn performance. Considering the time required for a diet to be reflected in newborn, we recommend Hippocampus guttulatus breeders to be fed on a high quality diet for at least 3 months prior the breeding periodThis study was financially supported by the Spanish Government with Project Hippoeco (Ref. CGL2015-68110-R, Ministerio de Ciencia, Innovación y Universidades and Fondos FEDER)Peer reviewe

Effects of black soldier fly (Hermetia illucens) enriched with Schizochytrium sp. on zebrafish (Danio rerio) reproductive performances

Nutrient quality, with emphasis on lipid and fatty acid composition of broodstock diet, is one of the major dietary factors influencing fish oocytes maturation, reproductive success and offspring quality/survival. The Black Soldier Fly (BFS) (Hermetia illucens) is a valuable insect species characterized by a balanced essential amino acid profile comparable to fishmeal and has been demonstrated to be an eco-friendly and low-cost protein source in fish diets. However, as regards lipids, BFS is usually characterized by a poor content in polyunsaturated fatty acids which are essential for fish during critical life-cycle stages including oocyte maturation and reproduction. In the present study, full-fat enriched BSF prepupae meal was obtained from BSF larvae reared on coffee by-product (coffee silverskin) enriched with 10% of Schizochytrium sp. Successively, five experimental diets containing different full-fat enriched BSF prepupae meal inclusion levels (corresponding to the 0, 25, 50, 75 and 100% fish meal replacement) were tested during a six-month feeding trial performed on zebrafish (Danio rerio) to investigate, for the first time, the physiological effects on female fish growth, stress response, lipid metabolism and reproductive performances. A multidisciplinary approach including biometric, gas-chromatographic, histological and molecular analyses was used during the present study to have a comprehensive overview of fish responses to the test diets. Results highlighted that up to 50% of fish meal replacement with enriched BSF meal did not impair zebrafish physiological responses while higher replacement levels (75 and 100%) negatively affected fish stress response, oocytes maturation stages, spawning and hatching success

Pre-breeding Diets in the Seahorse Hippocampus reidi: How Do They Affect Fatty Acid Profiles, Energetic Status and Histological Features in Newborn?

18 pages, 9 figures, 1 table.-- This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY)Seahorses (Hippocampus spp.) are exceptional marine species considering their reproductive patterns and other features. Due to the iconic characteristics of these fishes, aquarium trade, and research efforts have increased in the last years. Consequently, novel rearing techniques have been developed; however, there is a need for improvements on a series of issues, namely reproduction success enhancement. The tropical species Hippocampus reidi is the most traded seahorse but many aspects of breeding and its impact on the quality of neonates are still poorly understood. In the present study, we assessed the effects of two pre-breeding diets on newborn quality and viability considering biochemical characteristics, energetic status, and ultrastructural aspects of muscular tissue. During the whole pre-breeding season (5 months), the breeders were fed on one of the following diets: M0 (adult non-enriched Artemia) and M5 (adult non-enriched Artemia + mysidaceans). From the onset of the reproduction period, all breeders were fed for 6 months on diet M5. Breeding success and energetic status (ATP, total adenylic nucleotides, AEC, and NAD) of newborns resulted considerably enhanced in treatment M5. However, initial differences in neonates quality did not affect further newborn performance (survival and growth until day 7 after male’s pouch release) while gaining access to high-quality preys (copepods). Besides, morphological alterations in muscle tissue were not observed. The reproduction in the species followed a capital–income continuum pattern characterized by an initial mixed capital-income period (until 70–100 days since the onset of the breeding season) followed by an income breeding period with progressive exhaustion of body reserves, especially in M0-newborns. Interestingly, the effects of pre-breeding diets were also noticed in the second half of the breeding period. Our results seemed to indicate that the requirements in essential fatty acids in H. reidi are lower than in other seahorse species (e.g., Hippocampus guttulatus). Globally, the results achieved revealed that high-quality pre-breeding diets enhanced reproduction success and would likely result advantageous to improve newborn endurance in conditions of moderate starvation or sub-optimal feedingThis study was financially supported by the Spanish Government with Project Hippoeco (Ref. CGL2015-68110-R, MINECO) and Fondos FEDERPeer reviewe

Article salinity, temperature and ammonia acute stress response in seabream (Sparus aurata) juveniles: A multidisciplinary study

The present study aimed to investigate the acute response of gilthead seabream (Sparus aurata) juveniles exposed to temperature, salinity and ammonia stress. Radioimmunoassay was used to evaluate cortisol levels, whereas insulin-like growth factors (igf1 and igf2), myostatin (mstn), heat-shock protein 70 (hsp70) and glucocorticoid receptor (gr) gene expression was assessed trough Real-Time PCR. The presence and localization of IGF-I and HSP70 were investigated by immuno- histochemistry. In all the stress conditions, a significant increase in cortisol levels was observed reaching higher values in the thermic and chemical stress groups. Regarding fish growth markers, igf1 gene expression was significantly higher only in fish subjected to heat shock stress while, at 60 min, igf2 gene expression was significantly lower in all the stressed groups. Temperature and ammonia changes resulted in a higher mstn gene expression. Molecular analyses on stress response evidenced a time dependent increase in hsp70 gene expression, that was significantly higher at 60 min in fish exposed to heat shock and chemical stress. Furthermore, the same experimental groups were characterized by a significantly higher gr gene expression respect to the control one. Immunostaining for IGF-I and HSP70 antibodies was observed in skin, gills, liver, and digestive system of gilthead seabream juveniles