1,721,004 research outputs found
Future feeds in aquaculture: insects as a new ingredient for fish culture
Full text linkNell’ambito di un’acquacultura in continua espansione, la formulazione dei mangimi è stata identificata come uno dei principali fattori che possono comprometterne la sostenibilità ecologica ed economica. In questo contesto, la presente tesi di dottorato è stata incentrata sulla valutazione di una possibile transizione verso formulazioni mangimistiche innovative, caratterizzate da contenuti ridotti di materie prime convenzionali e non più sostenibili e dall’utilizzo della farina di prepupe di Hermetia illucens (mosca soldato nera) come ingrediente alternativo. Questa specie di insetto (i) è caratterizzata da un buon profilo nutrizionale e dalla presenza di molecole bioattive che possono esercitare un ruolo benefico sulla salute dei pesci e (ii) rappresenta una promettente soluzione per la possibilità sfruttare la sua grande efficienza di conversione del substrato di crescita per migliorare ulteriormente il suo profilo nutrizionale (specialmente in acidi grassi polinsaturi omega 3 a lunga catena) permettendo di introdurre il concetto di economia circolare nel settore dell’acquacoltura. Nella presente tesi, sono stati studiati gli effetti fisiologici di diversi livelli di inclusione di farina di prepupe di Hermetia illucens nella dieta, inizialmente su un modello sperimentale (zebrafish; Danio rerio) considerando il suo intero ciclo vitale e il possibile impatto sulla generazione successiva e, successivamente, su specie di interesse commerciale, una d’acqua dolce (storione siberiano, Acipenser baerii) e una marina (orata, Sparus aurata), dando particolare risalto alle performance di crescita, alla composizione in acidi grassi del filetto e alla salute del fegato e del tratto intestinale. Nel complesso, i risultati ottenuti hanno evidenziato che percentuali di inclusione di farina di prepupe rispetto a ingredienti di origine marina e vegetale fino al 50 e al 40 %, rispettivamente, possono promuovere la salute e il benessere dei pesci allevati e la qualità del prodotto. In particolare, le prove sperimentali incluse nella presente tesi rappresentano un esempio di come l’acquacoltura possa essere implementata con il riutilizzo di sottoprodotti derivati da altri settori e con la sostituzione parziale degli ingredienti convenzionali con alternative più sostenibili garantendo, al contempo, la produzione di pesci sani e la riduzione dell’impatto ambientale.In an ever-expanding aquaculture industry, aquafeed formulation has been identified as one of the key factors challenging the long-term ecological and economical sustainability of this sector. In this context, the present PhD thesis aimed to evaluate the possible transition to future feeds in aquaculture characterized by lower amounts of conventional marine- and plant- derived raw materials by using the Black Soldier Fly (Hermetia illucens; BSF) prepupae meal in aquafeed formulation. This insect species (i) is characterized by a good nutritional profile and by the presence of bioactive molecules that can exert a beneficial role on fish health and (ii) represents a promising solution due to the possibility to take advantage of its high feed conversion efficiency to ameliorate its nutritional profile (especially in terms of n3 long-chain polyunsaturated fatty acids) giving the possibility to introduce the circular economy concept to aquaculture sector. In the present thesis, the physiological effects of different dietary inclusion levels of BSF prepupae meal were investigated firstly on an experimental model (zebrafish; Danio rerio) considering its whole life cycle and the possible impact on the first filial generation and then focusing on a freshwater (Siberian sturgeon, Acipenser baerii) and a marine (gilthead seabream, Sparus aurata) farmed fish species, giving particular emphasis to fish growth, fillet fatty acids composition and liver/gut health. Overall, results obtained evidenced that dietary inclusion levels of BSF prepupae meal respect to marine- and plant -derived ingredients up to 50 and 40 %, respectively, can promote fish health, welfare and quality of the product. Specifically, the fish trials performed for the present PhD thesis represent an example of how aquaculture could be implemented with the re-use of land-produced by-products and with the partial substitution of conventional ingredients with more sustainable and eco-friendly ones like BSF prepupae meal, while sustaining the production of healthy fish and reducing the associated environmental footprint
A multidisciplinary experimental study on the effects of breeders diet on newborn seahorses (Hippocampus guttulatus)
Full text linkThe 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 reproduction success, which is dependent upon the administration of high quality diets to breeders. However, very 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 we used a wild pregnant male. 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 only mysidaceans (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 inflexion 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 three months prior the breeding period
New eco-sustainable feed in aquaculture: determination of potentially toxic elements in relation to the inclusion of Hermetia illucens raised on omega-3-enriched substrates
No full textSynthetic Feed Attractants in European Seabass (Dicentrarchus labrax) Culture: Effects on Growth, Health, and Appetite Stimulation
Full text linkSynthetic flavors from standardized processes have recently emerged as a promising and sustainable alternative to traditional feed attractants. In this study, two attractive (F25, cheese; F35, caramel) and one repulsive (F32-, coconut) synthetic flavors were individually added (1% w/w) to a commercial diet for European seabass (Dicentrarchus labrax) and tested over a 90-day feeding trial (30 fish per tank, in triplicate; initial weight 72.48 ± 8.04 g) to assess their impact on fish growth performance, welfare, and the modulation of brain appetite and monoaminergic pathways. None of the tested flavors negatively affected overall fish health. The F35 flavor enhanced feed intake (90.1 ± 5.6%) and growth (SGR 2.2 ± 0.2%) and positively influenced appetite-related and monoaminergic signals, thus being more effective than the F25 one (80.4 ± 3.2 and 1.6 ± 0.1%, respectively). A weekly feeding rotation between F35 and F25 (ROT group) resulted in suboptimal outcomes compared to F35 administration alone. The F32- flavor was not clearly perceived as strongly aversive by seabass and did not impair zootechnical performance. These findings highlight the potential of attractive synthetic flavors to improve diet palatability in a carnivorous species of commercial value, offering novel insights for more sustainable and cost-effective aquaculture feeding strategie
Mitigating Dietary Microplastic Accumulation and Oxidative Stress Response in European Seabass (Dicentrarchus labrax) Juveniles Using a Natural Microencapsulated Antioxidant
Full text linkAquafeed’s contamination by microplastics can pose a risk to fish health and quality since they can be absorbed by the gastrointestinal tract and translocate to different tissues. The liver acts as a retaining organ with the consequent triggering of oxidative stress response. The present study aimed to combine the use of natural astaxanthin with natural-based microcapsules to counteract these negative side effects. European seabass juveniles were fed diets containing commercially available fluorescent microplastic microbeads (1–5 μm; 50 mg/kg feed) alone or combined with microencapsulated astaxanthin (AX) (7 g/kg feed; tested for half or whole feeding trial—30 or 60 days, respectively). Fish from the different dietary treatments did not evidence variations in survival and growth performance and did not show pathological alterations at the intestinal level. However, the microplastics were absorbed at the intestinal level with a consequent translocation to the liver, leading, when provided solely, to sod1, sod2, and cat upregulation. Interestingly, the dietary implementation of microencapsulated AX led to a mitigation of oxidative stress. In addition, the microcapsules, due to their composition, promoted microplastic coagulation in the fish gut, limiting their absorption and accumulation in all the tissues analyzed. These results were supported by in vitro tests, which demonstrated that the microcapsules promoted microplastic coagula formation too large to be absorbed at the intestinal level and by the fact that the coagulated microplastics were released through the fish feces
Possible Dietary Effects of Insect-Based Diets across Zebrafish (Danio rerio) Generations: A Multidisciplinary Study on the Larval Phase
Full text linkInsects represent a valuable and sustainable alternative ingredient for aquafeed formulation. However, insect-based diets have often highlighted controversial results in different fish species, especially when high inclusion levels were used. Several studies have demonstrated that nutritional programming through parental feeding may allow the production of fish better adapted to use sub-optimal aquafeed ingredients. To date, this approach has never been explored on insect-based diets. In the present study, five experimental diets characterized by increasing fish meal substitution levels with full-fat Black Soldier Fly (Hermetia illucens; BSF) prepupae meal (0%, 25%, 50%, 75% and 100%) were used to investigate the effects of programming via broodstock nutrition on F1 zebrafish larvae development. The responses of offspring were assayed through biometric, gas chromatographic, histological, and molecular analyses. The results evidenced that the same BSF-based diets provided to adults were able to affect F1 zebrafish larvae fatty acid composition without impairing growth performances, hepatic lipid accumulation and gut health. Groups challenged with higher BSF inclusion with respect to fish meal (50%, 75% and 100%) showed a significant downregulation of stress response markers and a positive modulation of inflammatory cytokines gene expression. The present study evidences that nutritional programming through parental feeding may make it possible to extend the fish meal substitution level with BSF prepupae meal in the diet up to almost 100% without incurring the well-known negative side effects of BSF-based diet
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Replacement of fish meal with full fat Hermetia illucens modulates hepatic FXR signaling in juvenile rainbow trout (Oncorhynchus mykiss): Exploring a potential role of ecdysteroids
Full text linkThe present study was conducted to investigate the effects of fish meal (FM) replacement with full fat Hermetia illucens (HI) on the molecular mechanisms regulating lipid and bile salt (BA) homeostasis in rainbow trout (Oncorhynchus mykiss) juveniles. We thus explore the presence of 20-hydroxyecdysone (20E) in an insect meal-based diet and evaluate its potential involvement in regulating the molecular mechanisms/basis of FXR:RXR axis signaling. Ecdysteroids are a category of steroid hormones which bind a nuclear–receptor complex composed of ecdysone receptor (EcR) and ultraspiracle protein (USP) and regulate insect molting and metamorphosis. In all vertebrates, including fish, EcR-USP homologs are the Farnesoid X receptors (FXR) and the Retinoid X receptors (RXR), which are known to regulate crucial physiological and metabolic aspects, including BA synthesis and cholesterol homeostasis. In silico prediction indicates that 20E binds the heterodimeric complex with a binding affinity constant Kd equals to 610 ± 60 nM and affects positively the dimerization process. Results also demonstrated the coordinated increased expression of FXR and RXR, as well as their downstream target genes (i.e. short heterodimer partner 1 and 2) in rainbow trout fed diets containing HI meal. This latter finding was paralleled by a significant down-regulation of CYP7a1 and CYP8b1 gene expression together with a decrease in hepatic total cholesterol, triglyceride, and BA levels. Overall, our study suggested that FXR is a potential target for 20E content in insect meal and provided preliminary data on the potential role of ecdysteroids in regulating the metabolic status of teleost fish through modulation of FXR signaling in the enterohepatic system
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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