Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Lymphoid tissue in teleost gills : Variations on a theme
    Rességuier, Julien ; Dalum, Alf S. ; Pasquier, Louis Du; Zhang, Yaqing ; Koppang, Erling Olaf ; Boudinot, Pierre ; Wiegertjes, Geert F. - \ 2020
    Biology - open access biological sciences journal 9 (2020)6. - ISSN 2079-7737 - p. 1 - 14.
    Evolution - Fish - Gills - Ilt - Zap70

    In bony fish, the gill filaments are essential for gas exchanges, but also are vulnerable to infection by water‐borne microorganisms. Omnipresent across fish, gill‐associated lymphoid tissues (GIALT) regulate interactions with local microbiota and halt infection by pathogens. A special GIALT structure has recently been found in Salmonids, the interbranchial lymphoid tissue (ILT). However, the structural variation of GIALT across bony fish remains largely unknown. Here, we show how this critical zone of interaction evolved across fishes. By labeling a conserved T‐cell epitope on tissue sections, we find that several basal groups of teleosts possess typical ILT, while modern teleosts have lymphoepithelium of different shape and size at the base of primary gill filaments. Within Cypriniformes, neither body size variation between two related species, zebrafish and common carp, nor morphotype variation, did have a drastic effect on the structure of ILT. Thereby this study is the first to describe the presence of ILT in zebrafish. The ILT variability across fish orders seems to represent different evolutionary solutions to balancing trade‐offs between multiple adaptations of jaws and pharyngeal region, and immune responses. Our data point to a wide structural variation in gill immunity between basal groups and modern teleosts.

    Data from a survey of non-invasive sensors for monitoring animal welfare
    Kamphuis, Claudia ; Ouweltjes, Wijbrand ; Gonzales Rojas, Jose ; Breukelen, Anouk van - \ 2020
    Wageningen University & Research
    Cows - Fish - Pigs - Poultry - Sensors
    Dietary ingredient composition alters faecal characteristics and waste production in common carp reared in recirculation system
    Antony Jesu Prabhu, P. ; Fountoulaki, E. ; Maas, R. ; Heinsbroek, L.T.N. ; Eding, E.H. ; Kaushik, S.J. ; Schrama, J.W. - \ 2019
    Aquaculture 512 (2019). - ISSN 0044-8486
    DDGS - Feather meal - Fish - Non-starch polysaccharide - Pea - Starch - Sunflower meal

    Feed is a common factor influencing both fish growth and waste production in aquaculture. We examined the effect of different feed ingredients on the quantitative and qualitative aspects of faecal waste produced by common carp. Ingredients rich in (i) starch (field peas, PEA); (ii) protein (feather meal, FeM); (iii) insoluble non-starch polysaccharides, NSP (sunflower cake meal, SFM); or (iv) soluble NSP (wheat dried distillers grain with soluble, WDG) were studied. Five experimental diets were produced, a control diet produced from a basal mixture (CON) and four other diets (PEA, FeM, SFM and WDG) were prepared by replacing 30% of the basal mixture in CON with the respective test ingredient (70:30). Common carp juveniles (95 g, 15 fish per tank) were fed (restrictively, 22 g/kg0.8/d) the experimental diets for 7 weeks, in triplicate groups. Growth, body composition, energy and nutrient balances were significantly different; with highest growth recorded in CON and WDG; lowest in the FeM and SFM groups. Apparent digestibility coefficient (ADC) of dry matter, nutrients (protein, fat, carbohydrate, ash and phosphorus) and energy in the diets and ingredients were significantly altered between the groups (p < .001). PEA had the best ADC for macro-nutrients and energy, while ash and phosphorus were highest with WDG; SFM had the lowest ADC values for DM, fat, carbohydrate, energy, and phosphorus. The quantity, proximate composition and recovery percentage of the feaces (collected by settling) was significantly different between treatments (p < .001). Faeces recovery and solid removal efficiency were the highest in WDG, comparable to CON; and lowest in SFM. Physical characteristics of the feaces (stripped) indicated by dry matter content and stability were significantly affected by the ingredients only at day 26 and 29, respectively. However, changes in dry matter and stability over time (days) were significant in SFM and WDG (for DM); and all groups except SFM (stability). Osmolality and viscosity of the stripped faeces was unaffected. In summary, SFM resulted in significantly lower performance, low DM and nutrient digestibility, increased faecal loss, lower stability and removal efficiency. FeM lowered growth, protein and fat digestibility; with altered faecal chemical composition. WDG and PEA performed on par with control, if not better in certain aspects with respect to mineral availability and faecal recovery. Overall, 30% inclusion of the test ingredients not only affected growth, but also the waste production and removal efficiency by altering the physical and chemical characteristics of the faeces in common carp.

    The role of farm animals in a circular food system
    Zanten, Hannah H.E. Van; Ittersum, Martin K. Van; Boer, Imke J.M. De - \ 2019
    Global Food Security 21 (2019). - ISSN 2211-9124 - p. 18 - 22.
    Bio-economy - Circularity - Climate - Fish - Food production - Land use - Livestock - Sustainable diets

    If we use farm animals for what they are good at - converting by-products from the food system and grass resources into valuable food and manure - they can contribute significantly to human food supply, while at the same time reducing the environmental impact of the entire food system. By converting these so-called low-opportunity-cost feeds, farm animals recycle biomass and nutrients into the food system that would otherwise be lost to food production. Rearing animals under this circular paradigm, however, requires a transition from our current linear food system towards a circular one. Here we present a biophysical concept for the role of farm animals in a circular food system, essential for meeting dietary recommendations within the boundaries of our planet.

    Brominated flame retardants in animal derived foods in the Netherlands between 2009 and 2014
    Gebbink, Wouter A. ; Lee, Martijn K. van der; Peters, Ruud J.B. ; Traag, Wim A. ; Dam, Guillaume ten; Hoogenboom, Ron L.A.P. ; Leeuwen, Stefan P.J. van - \ 2019
    Chemosphere 234 (2019). - ISSN 0045-6535 - p. 171 - 178.
    Eggs - Fish - HBCDD - Meat - Milk - PBDE

    Polybrominated diphenylethers (PBDEs), hexabromocyclododecanes (HBCDDs) and tetrabromobisphenol A (TBBPA) were monitored in various foods from terrestrial and aquatic animal origin (>850 samples), collected in the Netherlands between 2009 and 2014. The terrestrial samples included meat/fat from 7 animal species (including bovines, pigs, broilers and sheep), bovine milk and hen eggs. Dominant PBDE congeners in these samples were BDE-47, -99, -100, -153 and -183. The meat/fat generally contained the highest ∑PBDE concentrations compared to eggs and milk, with meat from deer, horse and sheep containing the highest concentrations. Generally declining ∑PBDE concentrations were observed between 2009 and 2014, however, this was only significant in pig meat and hen's eggs. The aquatic samples included fillets from 18 species (including herring, haddock and salmon), brown crab parts, shrimp and mussels, and the highest ∑PBDE concentrations were seen in body parts of brown crab, herring, mackerel, salmon and sea bass (on wet weight basis). Patterns generally contained more congeners (i.e., BDE-28, -49 and -66) additional to the aforementioned congeners found in terrestrial samples. Herring, sea bass and brown crab (body parts) contained among the highest PBDE concentrations. TBBPA was only detected in 3 individual samples (bovine and broiler meat and haddock), while α-HBCDD was the dominant diastereomer detected in several terrestrial and aquatic samples. When detected, TBBPA and HBCDD concentrations were generally in the same order as ∑PBDE concentrations in the same sample types.

    Exploring fish microbial communities to mitigate emerging diseases in aquaculture
    Bruijn, Irene de; Liu, Yiying ; Wiegertjes, Geert F. ; Raaijmakers, Jos M. - \ 2018
    FEMS microbiology ecology 94 (2018)1. - ISSN 0168-6496
    Aquaculture - Beneficial microbes - Emerging diseases - Fish - Microbiomes
    Aquaculture is the fastest growing animal food sector worldwide and expected to further increase to feed the growing human population. However, existing and (re-)emerging diseases are hampering fish and shellfish cultivation and yield. For many diseases, vaccination protocols are not in place and the excessive use of antibiotics and other chemicals is of substantial concern. A more sustainable disease control strategy to protect fish and shellfish from (re-)emerging diseases could be achieved by introduction or augmentation of beneficial microbes. To establish and maintain a 'healthy' fish microbiome, a fundamental understanding of the diversity and temporal-spatial dynamics of fish-associated microbial communities and their impact on growth and health of their aquatic hosts is required. This review describes insights in the diversity and functions of the fish bacterial communities elucidated with next-generation sequencing and discusses the potential of the microbes to mitigate (re-)emerging diseases in aquaculture.
    Differences in fraud vulnerability in various food supply chains and their tiers
    Ruth, S.M. van; Luning, P.A. ; Silvis, I.C.J. ; Yang, Y. ; Huisman, W. - \ 2018
    Food Control 84 (2018). - ISSN 0956-7135 - p. 375 - 381.
    Bananas - Fish - Meat - Milk - Olive oil - Spices
    Food fraud results from the interaction of motivated offenders with opportunities, and lack of control measures. The vulnerability to food fraud varies across chain actors (tiers) though, but insights on prime fraud drivers and enablers, as well as chain areas where vulnerabilities might exist are lacking. In the current study the fish, meat, milk, olive oil, organic bananas, and spice supply chains were assessed for their fraud vulnerabilities. The differences and similarities in vulnerabilities across the supply chains, as well as between groups of chain actors were evaluated using the SSAFE food fraud vulnerability assessment tool. Multiple correspondence analysis and agglomerative hierarchical clustering were applied for exploratory data analysis, and differences between chains and actors were assessed by analysis of variance and post-hoc tests. Thirteen fraud factors related to opportunities and motivations scored high across all supply chains indicating their importance as fraud drivers and enablers. Control measures varied considerably across supply chains and actor groups, with technical (hard) controls generally being more in place than managerial (soft) controls. Approximately half of the fraud factors were impacted by the type of commodity chain, and one out of seven of the fraud factors by the actor group. From the current sample group overall fraud vulnerability appeared highest for the spice chain, which was followed by the olive oil, meat, fish, milk and organic banana chains. Among the actor groups, the wholesale/traders group appeared most vulnerable, followed by retailers and processors. The current results provide new insights in the fraud factors determining fraud vulnerability in various supply chains, and the (dis)similarities in fraud vulnerability across supply chains and actor groups which helps to combat future food fraud.
    The effect of phytase, xylanase and their combination on growth performance and nutrient utilization in Nile tilapia
    Maas, Roel M. ; Verdegem, Marc C.J. ; Dersjant-Li, Yueming ; Schrama, Johan W. - \ 2018
    Aquaculture 487 (2018). - ISSN 0044-8486 - p. 7 - 14.
    Fish - Nitrogen balance - Phytase - Synergy - Xylanase
    Increasing the inclusion rate of plant ingredients will increase the content of non-starch polysaccharides (NSP) and phytate in the fish feed. Both NSP and phytate are undesired in fish feed due to their anti-nutritional properties. The main objective of the present study was to assess the impact of exogenous enzyme supplementation on growth, body composition, digestibility and the energy, nitrogen and phosphorus balances in Nile tilapia. Four experimental diets were tested in a 2 × 2 factorial arrangement of treatments. The first factor was phytase supplementation at a dose of either 0 or 1000 FTU/kg and the second factor was xylanase supplementation at a dose of 0 or 4000 U/kg. This resulted in a control diet (CON-CON) without enzymes, phytase diet (PHY-CON), xylanase diet (CON-XYL) and a diet with both xylanase and phytase (PHY-XYL). In total 24 tanks (6 replicates/treatment) were used with 30 (mean initial body weight 42 g) fish each. Fish were restrictively (80% of expected satiation) fed the experimental diets for 38 days. Growth was significantly affected by the interaction between phytase and xylanase supplementation (P < 0.05), showing a synergism between both enzymes. Growth at the CON-CON and CON-XYL diets were similar, whereas fish fed the PHY-CON had an improved growth. The effect of phytase supplementation on growth was further enhanced when xyalanse was supplemented (PHY-XYL diet). Phytase significantly improved the digestibility of dry matter, crude protein, carbohydrates, energy, ash, phosphorus and calcium (P < 0.001). Xylanase enhanced the digestibility of dry matter, crude protein, carbohydrates and energy significantly (P < 0.05). In contrast to growth, there was no significant synergetic effect of the combination of phytase and xylanase on the digestibility (P > 0.05). The significant synergetic effect of the combination of phytase and xylanase on growth was not reflected on the digestibility (P > 0.05). The nitrogen balance showed that the synergism on growth was predominantly due the significant synergistic effect of phytase and xylanase on the protein retention (P = 0.005). Both xylanase and phytase showed to be an effective tool to improve the nutrient availability and growth in Nile tilapia. Fish fed the diet supplemented with both phytase and xylanase had a significantly higher growth than all other treatments.
    Improving feed efficiency in fish using selective breeding : A review
    Verdal, Hugues de; Komen, Hans ; Quillet, Edwige ; Chatain, Béatrice ; Allal, François ; Benzie, John A.H. ; Vandeputte, Marc - \ 2018
    Reviews in Aquaculture 10 (2018)4. - ISSN 1753-5123 - p. 833 - 851.
    Feed conversion ratio - Feed efficiency - Feed intake - Fish - Genetics - Selection

    Improving feed efficiency (FE) is key to reducing production costs in aquaculture and to achieving sustainability for the aquaculture industry. Feed costs account for 30-70% of total production costs in aquaculture; much work has been done on nutritional and husbandry approaches to improve FE but only a limited amount of research has been devoted to using genetics, despite its potential. This paper reviews past work to improve FE in fish using selective breeding and assess future directions. Direct selection on FE traits requires methods to measure individual feed consumption and estimate FE efficiently and accurately. This is particularly difficult to do in fish because of the environment in which they live. Many of the published studies on FE were found to be inaccurate because of methodological problems. The relatively low heritability estimates of FE traits in fish published to date are probably partly as a result of inaccurate measurements of feed intake. Improving ways to measure the individual feed intake with high accuracy will be critical to the successful application of genetics to improving FE. Indirect selection criteria that could be used to improve FE (including growth after starvation/refeeding, body composition, neuropeptides or hormone levels) are discussed. Promising approaches to measuring feed intake accurately that may enable these studies to be undertaken are identified. More work using these will be needed prior to assessing the practicality of the introduction of direct or indirect traits for FE in fish genetic improvement programmes.

    Editorial: Physiological adaptations to swimming in fish
    Planas, Josep V. ; Palstra, Arjan P. ; Magnoni, Leonardo J. - \ 2017
    Frontiers in Physiology 8 (2017). - ISSN 1664-042X - 2 p.
    Fish - Growth - Performance - Swimming economy - Swimming exercise
    Changes in fish communities on a small spatial scale, an effect of increased habitat complexity by an offshore wind farm
    Hal, R. van; Griffioen, A.B. ; Keeken, O.A. van - \ 2017
    Marine Environmental Research 126 (2017). - ISSN 0141-1136 - p. 26 - 36.
    Acoustic camera - Community effects - Fish - Hard substrates - North sea - Schooling - Static gear - Wind power
    The number of offshore wind farms (OWF) is increasing to meet the demands for renewable energy. The piles and hard substrate surrounding these piles creates new habitat for species with preference to hard substrates. We studied the impact of this hard substrate on the fish community in a Dutch OWF in the sandy southern North Sea, which had been in operation for five years. Multi-mesh gillnets were placed near the OWF structures on the hard substrate protection revetments and on the sandy bottom in the middle of the farm. The catches indicated attraction of cod, pouting, bullrout and edible and velvet crab, while attraction to the sandy habitat was shown for flatfish and whiting. Further, two species previously not caught in this area, goldsinny wrasse and grey trigger fish, were caught on the hard substrate. In addition a Dual-Frequency Identification Sonar (DIDSON) was used to record transects through the farm to observe individual fish in the water column throughout the farm and very near the OWF structures. High abundances of fish near the structure were observed during some days, while during other days equal distribution of fish in the area was observed. The area around the structures is thus only used temporarily for shelter or feeding. The DIDSON also allowed looking at the aggregation level of the fish. Seasonally the aggregation level differed most likely due to different species occurring in the area. In April, most fish were aggregated in schools, while in summer most observations were individual fish or loose aggregations. The wind farm structures had limited effect on the aggregation level compared to season or weather conditions.
    Estrogen-dependent seasonal adaptations in the immune response of fish
    Szwejser, Ewa ; Kemenade, Lidy van; Maciuszek, Magdalena ; Chadzinska, Magdalena - \ 2017
    Hormones and Behavior 88 (2017). - ISSN 0018-506X - p. 15 - 24.
    Aromatase - Endocrine disrupting compounds - Estrogen receptors - Estrogens - Fish - Season

    Clinical and experimental evidence shows that estrogens affect immunity in mammals. Less is known about this interaction in the evolutionary older, non-mammalian, vertebrates. Fish form an excellent model to identify evolutionary conserved neuroendocrine-immune interactions: i) they are the earliest vertebrates with fully developed innate and adaptive immunity, ii) immune and endocrine parameters vary with season, and iii) physiology is constantly disrupted by increasing contamination of the aquatic environment.Neuro-immuno-endocrine interactions enable adaption to changing internal and external environment and are based on shared signaling molecules and receptors. The presence of specific estrogen receptors on/in fish leukocytes, implies direct estrogen-mediated immunoregulation. Fish leukocytes most probably are also capable to produce estrogens as they express the . cyp19a and . cyp19b - genes, encoding aromatase cytochrome P450, the enzyme critical for conversion of C19 steroids to estrogens.Immunoregulatory actions of estrogens, vary among animal species, and also with dose, target cell type, or physiological condition (e.g., infected/non-infected, reproductive status). They moreover are multifaceted. Interestingly, season-dependent changes in immune status correlate with changes in the levels of circulating sex hormones. Whereas E2 circulating in the bloodstream is perhaps the most likely candidate to be the physiological mediator of systemic immune-reproductive trade-offs, leukocyte-derived hormones are hypothesized to be mainly involved in local tuning of the immune response. Contamination of the aquatic environment with estrogenic EDCs may violate the delicate and precise allostatic interactions between the endogenous estrogen system and the immune system. This has negative effects on fish health, but will also affect the physiology of its consumers.

    Water exchange rate in RAS and dietary inclusion of micro-minerals influence growth, body composition and mineral metabolism in common carp
    Antony Jesu Prabhu, P. ; Kaushik, S.J. ; Geurden, I. ; Stouten, T. ; Fontagné-dicharry, S. ; Veron, V. ; Mariojouls, C. ; Verreth, J.A.J. ; Eding, E.H. ; Schrama, J.W. - \ 2017
    Aquaculture 471 (2017). - ISSN 0044-8486 - p. 8 - 18.
    Recirculation aquaculture system - Minerals - Requirement - Metabolism - Fish
    Recirculation aquaculture systems (RASs) operated at low water exchange rates are known to accumulate minerals in the water. This study examined the dietary mineral requirement and metabolism in common carp reared in RAS of contrasting water exchange rates. Two independent RAS (water exchange rates, 70 vs. 2000 L/kg feed) and five experimental diets with graded levels of micro-mineral premix inclusion (0.0, 0.3, 0.6, 1.0 and 1.5%) were tested in a 2 × 5 factorial arrangement. Common carp fingerlings (8.5 g) were reared in either of the RAS and fed the experimental diets in triplicates for 8 weeks at 24 °C. Water quality, fish growth, body composition, tissue mineral concentrations, blood haemoglobin and haematocrit levels, biochemical and molecular markers of oxidative stress, mineral uptake and metabolism were studied. RAS operated at low water exchange rate showed significantly high conductivity, nitrate, nitrite and dissolved mineral concentrations in water. A tendency for higher growth, significantly higher whole body mineral levels except Cu and Zn were observed in fish reared in RAS with high accumulation of minerals (H-RAS). Of the micro-minerals studied, effect of RAS on the minimal dietary inclusion level was significant only for Se; lower in fish reared in the H-RAS (0.28 mg/kg) compared to L-RAS (0.32 mg/kg). Increasing premix inclusion decreased growth and feed efficiency, increased the whole body concentration of Cu, Se and Zn, while Fe and Mn were unaffected. Plasma P, Ca, K and Mn were higher and haematocrit was lower in H-RAS reared fish; plasma mineral levels were also influenced by premix inclusion. Enzymes involved in micro-mineral uptake and metabolism (ferric reductase, cupric reductase and alkaline phosphatase) and oxidative stress markers (glutathione peroxidase, catalase, glutathione reductase and glutathione S-transferase) were analysed in gill, intestine and liver. In fish reared in H-RAS, reduced glutathione peroxidase (GPx) and increased glutathione reductase (GR) activities were observed in liver and intestine, respectively. Activity of GPx in all the analysed tissues increased with premix supplementation. Differential regulation in mRNA expression of molecular markers related to micro-mineral uptake, metabolism and oxidative stress were observed in the tissues in response to RAS and premix inclusion. To conclude, fish reared in high accumulation RAS had higher mineral levels in whole body and vertebrae, but did not result in a lower estimate of micro-minerals, except for Se. Difference in rearing system had multiple effects on the physiology and metabolism of fish on the whole, apart from mineral balance alone.
    Cortisol and testosterone accumulation in a low pH recirculating aquaculture system for rainbow trout (Oncorhynchus mykiss)
    Mota, Vasco C. ; Martins, Catarina I.M. ; Eding, Ep H. ; Canário, Adelino V.M. ; Verreth, Johan A.J. - \ 2017
    Aquaculture Research 48 (2017)7. - ISSN 1355-557X - p. 3579 - 3588.
    Fish - Hormones - Recirculating aquaculture - Steroids - Water

    Steroids accumulate in recirculating aquaculture system (RAS), although explanatory factors for such accumulation are still poorly explored. This study investigated the effect of water exchange rate and pH in six replicated RAS on the concentration of the stress hormone cortisol in rainbow trout blood plasma and in the holding water and of the sex steroids testosterone, 11-ketotestosterone (11-KT) and 17,20β-dihydroxypregn-4-en-3-one (17,20β-P) over a 70-day experimental period. Three combinations of water exchange rate and pH were used each treatment, with two replications: (i) high water exchange rate (±1700 L kg-1 feed) and neutral pH (±7.3), (ii) low water exchange rate (±500 L kg-1 feed) and neutral pH (±7.3) and (iii) low water exchange rate (±500 L kg-1 feed) and low pH (±5.8). Plasma cortisol concentrations at day 70 were higher (24.4 ± 9.5 ng mL-1) for fish kept at low pH when compared to fish kept at neutral pH (12.0 ± 0.1 and 8.7 ± 0.2 ng mL-1). Water cortisol and testosterone concentrations at day 35 were higher at low pH than at neutral pH, whereas water 11-KT and 17,20β-P did not differ among treatments. At day 70, there were no significant differences between low and high pH. These results demonstrate that low pH contributes to increased plasma cortisol concentrations and to its accumulation in water, possibly indicating a stress response to low pH. The higher concentration of testosterone but not of the other sex hormones point to unspecified reproductive effects that need further investigation.

    The effect of type of carbohydrate (starch vs. nonstarch polysaccharides) on nutrients digestibility, energy retention and maintenance requirements in Nile tilapia
    Haidar, Mahmoud N. ; Petie, Mischa ; Heinsbroek, Leon T.N. ; Verreth, Johan A.J. ; Schrama, Johan W. - \ 2016
    Aquaculture 463 (2016). - ISSN 0044-8486 - p. 241 - 247.
    Energy utilization - Non-starch polysaccharides - Maintenance requirements - Fish
    For Nile tilapia, the energetic value of non-starch polysaccharides (NSP) was compared to starch. It was assessed if carbohydrate type (NSP vs. starch) affected the energetic utilization for growth (KgDE) and the energy requirements for maintenance (DEm). Eighteen groups of fish were assigned in 2 × 3 factorial design: two diets, with either a high NSP or high starch content; and three feeding levels (low, medium or satiation). The NSP diet contained 70% of the starch diet supplemented with 30% dried distillers grains with solubles. Nutrients digestibility, nitrogen and energy balances were measured. All nutrients digestibility decreased with increasing feeding level (P < 0.001). Diet type (NSP vs. starch) affected the digestibility of all nutrients except for dry matter and fat. NSP of both diets were digested and the NSP digestibility ranged between 23% and 73%. Averaged over feeding levels, 5% and 17% of the total digestible energy originated from NSP at the starch and NSP diet, respectively. Although the digestible energy intake was similar, the contrast in type of carbohydrates between the diets resulted in lower energy retention with the NSP rich diet (P < 0.05). Despite this impact on energy retention, both DEm and kgDE were not significantly influence by diet. However, DEm was numerically higher (96 vs. 110 kJ kg-0.8 BW d-1) and kgDE was numerically lower (65% vs. 58%) at the NSP diet compared to the starch diet. In conclusion, NSP are digested by Nile tilapia. Digested NSP are less well utilized for growth, which is reflected by a lower energy retention in fish and is due to the slightly higher DEm in combination with a slightly lower kgDE. Statement of relevance: Scarcity of fishmeal and -oil combined with the fast growing aquaculture sector, result in diversification of feed ingredients in fish-feeds. Plant ingredients as protein source become more important, which also increases the dietary carbohydrate content including non-starch polysaccharides (NSP). This paper provides information on the nutritional value of NSP in tilapia. This will eventually lead to improved fish-feed formulations.
    Long-lived effects of administering β-glucans : Indications for trained immunity in fish
    Petit, Jules ; Wiegertjes, Geert F. - \ 2016
    Developmental and Comparative Immunology 64 (2016). - ISSN 0145-305X - p. 93 - 102.
    Fish - Immune-stimulation - Innate immunity - Teleost - Trained immunity - β-glucans

    Over the past decades, it has become evident that immune-modulation of fish with β-glucans, using injection, dietary or even immersion routes of administration, has stimulating but presumed short-lived effects on both intestinal and systemic immunity and can increase protection against a subsequent pathogenic challenge. Although the exact effects can be variable depending on, among others, fish species and administration route, the immune-stimulating effects of β-glucans on the immune system of fish appear to be universal. This review provides a condensed update of the most recent literature describing the effects of β-glucans on the teleost fish immune system. We shortly discuss possible mechanisms influencing immune-stimulation by β-glucans, including microbial composition of the gut, receptor recognition and downstream signalling. Of interest, in mammalian monocytes, β-glucans are potent inducers of trained immunity. First, we screened the literature for indications of this phenomenon in fish. Criteria that we applied include indications for at least one out of three features considered characteristic of trained immunity; (i) providing protection against a secondary infection in a T- and B-lymphocyte independent manner, (ii) conferring increased resistance upon re-infection and, (iii) relying on key roles for innate immune cell types such as natural killer cells and macrophages. We conclude that several indications exist that support the notion that the innate immune system of teleost fish can be trained. Second, we screened the literature for indications of long-lived effects on innate immunity of fish after administering β-glucans, a criterion which could help to identify key roles for macrophages on resistance to infection. We discuss whether β-glucans, as well-known immune-stimulants, are able to train the immune system of fish and argue in favour of further studies designed to specifically investigate this phenomenon in fish.

    Effectiveness of tail-first dry electrical stunning, followed by immersion in ice water as a slaughter (killing) procedure for turbot (Scophthalmus maximus) and common sole (Solea solea)
    Daskalova, A.H. ; Bracke, M.B.M. ; Vis, J.W. van de; Roth, B. ; Reimert, H.G.M. ; Burggraaf, D. ; Lambooij, E. - \ 2016
    Aquaculture 455 (2016). - ISSN 0044-8486 - p. 22 - 31.
    Behaviour - EEG - Electrical stunning - Fish - Slaughter - Welfare

    To protect the welfare of fish at slaughter, these animals should be rendered unconscious and insensible prior to killing. Furthermore, the state of unconsciousnessmust be long enough to allowkillingwithout recovery. The objective of this study was to determine the stunner settings for effective tail-first dry electrical stunning of turbot (Scophthalmusmaximus) and common sole (Solea solea). The fish were separated in two batches (B1 and B2). The turbot and sole in B1were subjected to a short tail-first stun lasting for 1 s and after 1 min of recovery to a second, longer (20 s) stun. The fish in B2were exposed to a single long (20 s) stun, whichwas tail-first in sole, but headfirst in turbot. The short stun was applied to verify that the loss of consciousness was instant (i.e. within 1 s), whereas the long stun (followed by immersion in ice water) was performed with the aim of showing that it is feasible to kill the fish without recovery. Loss of consciousness and sensibility were assessed using electrophysiological (EEG and ECG) and behavioural parameters. After administering a current of 2.39 ± 0.91 Arms by applying 125.5 ± 0.6 Vrms (100 Hz) in turbot and 1.22 ± 0.68 Arms by applying 152.4 ± 0.5 Vrms in sole for 1 s, 25 out of 26 turbot and 9 out of 10 sole in B1 exhibited EEG patterns showing that the fish were rendered unconscious instantly. The long tail-first exposure of turbot in B1 to 3.88 ± 1.26 Arms for 1 s, followed by 1.44 ± 0.41 Arms for 19 s, followed by immersion in ice water, led to an irrecoverable stun in 21 out of 22 fish, whereas the long head-first stunning of turbot in B2 (n = 13) resulted in passing 1.27 ± 0.40 Arms for 1 s and 0.65 ± 0.21 Arms for 19 s through the fish and no recovery during chilling. After the long, tail-first exposure of sole in B1 (n = 9) and B2 (n = 22) to 1.18± 0.49 Arms for 1 s+0.35 ± 0.22 Arms for 19 s, and 1.20± 0.59 Arms for 1 s + 0.36 ± 0.15 Arms for 19 s, respectively, none of the fish regained consciousness during the chilling. We conclude that the tail-first electrical stunning, followed by immersion in ice water can be developed into an effective stunning and killing method for turbot and sole.

    Polarization of immune responses in fish : The 'macrophages first' point of view
    Wiegertjes, Geert F. ; Wentzel, Annelieke S. ; Spaink, Herman P. ; Elks, Philip M. ; Fink, Inge R. - \ 2016
    Molecular Immunology 69 (2016). - ISSN 0161-5890 - p. 146 - 156.
    Arginase - Fish - INOS - LPS - Macrophage polarization - Zebrafish

    In this review, we support taking polarized immune responses in teleost fish from a 'macrophage first' point of view, a hypothesis that reverts the dichotomous T helper (TH)1 and TH2 driving forces by building on the idea of conservation of innate immune responses in lower vertebrates. It is plausible that the initial trigger for macrophage polarization into M1 (inflammation) or M2 (healing) could rely only on sensing microbial/parasite infection or other innate danger signals, without the influence of adaptive immunity. Given the long and ongoing debate on the presence/absence of a typical TH1 cytokine environment and, in particular, TH2 cytokine environment in fish immune responses, it stands out that the presence of macrophages with polarized phenotypes, alike M1 and M2, have been relatively easy to demonstrate for fish. We summarize in short present knowledge in teleost fish on those cytokines considered most critical to the dichotomous development of TH1/M1 and TH2/M2 polarization, in particular, but not exclusively, interferon-γ and interleukin (IL)-4/IL-13. We review, in more detail, polarization of fish immune responses taken from the macrophage point of view for which we adopted the simple nomenclature of M1 and M2. We discuss inducible nitric oxide synthase, or NOS-2, as a reliable M1 marker and arginase-2 as a reliable M2 marker for teleost fish and discuss the value of these macrophage markers for the generation of zebrafish reporter lines to study M1/M2 polarization in vivo.

    Contrasting the roles of section length and instream habitat enhancement for river restoration success : A field study of 20 European restoration projects
    Hering, Daniel ; Aroviita, Jukka ; Baattrup-Pedersen, Annette ; Brabec, Karel ; Buijse, Tom ; Ecke, Frauke ; Friberg, Nikolai ; Gielczewski, Marek ; Januschke, Kathrin ; Köhler, Jan ; Kupilas, Benjamin ; Lorenz, Armin W. ; Muhar, Susanne ; Paillex, Amael ; Poppe, Michaela ; Schmidt, Torsten ; Schmutz, Stefan ; Vermaat, Jan ; Verdonschot, Piet F.M. ; Verdonschot, Ralf C.M. ; Wolter, Christian ; Kail, Jochem - \ 2015
    Journal of Applied Ecology 52 (2015)6. - ISSN 0021-8901 - p. 1518 - 1527.
    Aquatic macrophytes - Benthic invertebrates - Fish - Floodplain - Flow patterns - Food web - Ground beetles - Riparian vegetation - Stable isotopes

    Restoration of river hydromorphology often has limited detected effects on river biota. One frequently discussed reason is that the restored river length is insufficient to allow populations to develop and give the room for geomorphological processes to occur. We investigated ten pairs of restored river sections of which one was a large project involving a long, intensively restored river section and one represented a smaller restoration effort. The restoration effect was quantified by comparing each restored river section to an upstream non-restored section. We sampled the following response variables: habitat composition in the river and its floodplain, three aquatic organism groups (aquatic macrophytes, benthic invertebrates and fish), two floodplain-inhabiting organism groups (floodplain vegetation, ground beetles), as well as food web composition and land-water interactions reflected by stable isotopes. For each response variable, we compared the difference in dissimilarity of the restored and nearby non-restored section between the larger and the smaller restoration projects. In a second step, we regrouped the pairs and compared restored sections with large changes in substrate composition to those with small changes. When comparing all restored to all non-restored sections, ground beetles were most strongly responding to restoration, followed by fish, floodplain vegetation, benthic invertebrates and aquatic macrophytes. Aquatic habitats and stable isotope signatures responded less strongly. When grouping the restored sections by project size, there was no difference in the response to restoration between the projects targeting long and short river sections with regard to any of the measured response variables except nitrogen isotopic composition. In contrast, when grouping the restored sections by substrate composition, the responses of fish, benthic invertebrates, aquatic macrophytes, floodplain vegetation and nitrogen isotopic composition were greater in sections with larger changes in substrate composition as compared to those with smaller changes. Synthesis and applications. The effects of hydromorphological restoration measures on aquatic and floodplain biota strongly depend on the creation of habitat for aquatic organisms, which were limited or not present prior to restoration. These positive effects on habitats are not necessarily related to the restored river length. Therefore, we recommend a focus on habitat enhancement in river restoration projects. The effects of hydromorphological restoration measures on aquatic and floodplain biota strongly depend on the creation of habitat for aquatic organisms, which were limited or not present prior to restoration. These positive effects on habitats are not necessarily related to the restored river length. Therefore, we recommend a focus on habitat enhancement in river restoration projects.

    Occurrence of pharmaceuticals and endocrine disrupting compounds in macroalgaes, bivalves, and fish from coastal areas in Europe
    Álvarez-Muñoz, D. ; Rodríguez-Mozaz, S. ; Maulvault, A.L. ; Tediosi, A. ; Fernández-Tejedor, M. ; Heuvel, F. Van den; Kotterman, M. ; Marques, A. ; Barceló, D. - \ 2015
    Environmental Research 143 (2015). - ISSN 0013-9351 - p. 56 - 64.
    Algae - Bivalves - Endocrine disrupting compounds - Fish - Pharmaceutical - Prioritisation

    The ocurrence and levels of PhACs, Endocrine Disrupting and related Compounds (EDCs) in seafood from potential contaminated areas in Europe has been studied. Macroalgae (S. accharina latissima and Laminaria digitata), bivalves (Mytilus galloprovincialis, Mytilus spp., Chamalea gallina and Crassostrea gigas) and fish (Liza aurata and Platichthys flesus) from Portugal, Spain, Italy, Netherlands, and Norway were analysed following 4 different analytical protocols depending on the organism and target group of contaminants. The results revealed the presence of 4 pharmaceutical compounds in macroalgae samples, 16 in bivalves and 10 in fish. To the best of our knowledge, this is the first time that PhACs have been detected in marine fish and in macroalgae. Besides, this is also the first time that dimetridazole, hydrochlorothiazide and tamsulosin have been detected in biota samples. The highest levels of PhACs corresponded to the psychiatric drug velanfaxine (up to 36.1 ng/g dry weight (dw)) and the antibiotic azithromycin (up to 13.3 ng/g dw) in bivalves from the Po delta (Italy). EDCs were not detected in macroalgae samples, however, the analysis revealed the presence of 10 EDCs in bivalves and 8 in fish. The highest levels corresponded to the organophosphorus flame retardant tris(2-butoxyethyl)phosphate (TBEP) reaching up to 98.4 ng/g dw in mullet fish from the Tagus estuary. Bivalves, in particular mussels, have shown to be good bioindicator organisms for PhACs and fish for EDCs. Taking into consideration the concentrations and frequencies of detection of PhACs and EDCs in the seafood samples analysed, a list of candidates' compounds for priorization in future studies has been proposed.

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