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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    Forced sustained swimming exercise at optimal speed enhances growth of juvenile yellowtail kingfish (Seriola lalandi)
    Palstra, A.P. ; Mes, D. ; Kusters, K. ; Roques, J.A.C. ; Flik, G. ; Kloet, K. ; Blonk, R.J.W. - \ 2015
    Frontiers in Physiology 5 (2015). - ISSN 1664-042X - 11 p.
    trout oncorhynchus-mykiss - salmon salmo-salar - salvelinus-alpinus l - bass morone-saxatilis - rainbow-trout - atlantic salmon - seriola-lalandi - arctic charr - muscular development - disease resistance
    Swimming exercise at optimal speed may optimize growth performance of yellowtail kingfish in a recirculating aquaculture system. Therefore, optimal swimming speeds (U-opt in m s(-1) or body lengths s(-1), BL s(-1)) were assessed and then applied to determine the effects of long-term forced and sustained swimming at U-opt on growth performance of juvenile yellowtail kingfish. Uopt was quantified in Blazka-type swim-tunnels for 145, 206, and 311 mm juveniles resulting in values of: (1) 0.70 m s(-1) or 4.83 BL s(-1), (2) 0.82 m s(-1) or 3.25 BL s(-1), and (3) 0.85 m s(-1) or 2.73 BL s(-1). Combined with literature data from larger fish, a relation of U-opt (BL s(-1)) = 234.07(BL)(-0.779) (R-2 = 0.9909) was established for this species. Yellowtail kingfish, either forced to perform sustained swimming exercise at an optimal speed of 2.46 BL s(-1) ("swimmers") or allowed to perform spontaneous activity at low water flow ("resters") in a newly designed 3600 L oval flume (with flow created by an impeller driven by an electric motor), were then compared. At the start of the experiment, ten fish were sampled representing the initial condition. After 18 days, swimmers (n = 23) showed a 92% greater increase in BL and 46% greater increase in BVV as compared to resters (n = 23). As both groups were fed equal rations, feed conversion ratio (FCR) for swimmers was 1.21 vs. 1.74 for resters. Doppler ultrasound imaging showed a statistically significant higher blood flow (31%) in the ventral aorta of swimmers vs. resters (44 +/- 3 vs. 34 +/- 3 mL min(-1), respectively, under anesthesia). Thus, growth performance can be rapidly improved by optimal swimming, without larger feed investments.
    The impact of elevated water nitrite concentration on physiology, growth and feed intake of African catfish Clarias gariepinus (Burchell 1822)
    Roques, J.A.C. ; Schram, E. ; Spanings, T. ; Schaik, T. van; Abbink, W. ; Boerrigter, J. ; Vries, P. de; Vis, J.W. van de; Flik, G. - \ 2015
    Aquaculture Research 46 (2015)6. - ISSN 1355-557X - p. 1384 - 1395.
    channel catfish - rainbow-trout - fresh-water - ictalurus-punctatus - oncorhynchus-mykiss - na+/k+-atpase - carpio l. - toxicity - chloride - mechanism
    The nitrite threshold concentration in rearing water of African catfish (Clarias gariepinus) was assessed. African catfish with an initial mean (SD) weight of 219.7 (57.8) g were exposed to an increasing range of water nitrite from 6 (Control) to 928 µM nitrite for 28 days. Mean (SD) plasma nitrite concentrations increased from 5.0 (3.6) to 32.5 (12.6) µM at 928 µM ambient nitrite. The increase in nitrite was accompanied by gradual increase in plasma nitrate from 41.6 (28.4) µM to 420.2 (106.4) µM. Haematocrit, haemoglobin, methemoglobin, plasma concentrations of cortisol, glucose, lactate, osmolality, gill morphology and branchial Na+/K+-ATPase activity were not affected. Feed intake, final weight, SGR, FCR and mortality were not affected. We advise not to exceed a water nitrite concentration of 43 µM (0.6 mg L-1 NO2--N) to prevent the risk of reduced growth and feed intake in African catfish aquaculture.
    Preparation of functional lupine protein fractions by dry separation
    Pelgrom, P.J.M. ; Berghout, J.A.M. ; Goot, A.J. van der; Boom, R.M. ; Schutyser, M.A.I. - \ 2014
    Food Science and Technology = Lebensmittel-Wissenschaft und Technologie 59 (2014)2 part 1. - ISSN 0023-6438 - p. 680 - 688.
    air classification - isoelectric precipitation - carbohydrate-composition - oncorhynchus-mykiss - rainbow-trout - fish-meal - digestibility - angustifolius - ultrafiltration - powders
    Lupine protein concentrate is a promising ingredient that can be obtained by a combination of milling and air classification, generally called dry fractionation. This is a more sustainable route than conventional wet extraction and delivers a protein concentrate with native functional properties. Critical is the detachment of the protein bodies from other seed components during milling. Ideally, the protein bodies are released during milling, whereas the other components remain in larger particles (D0.5 > 40 µm) to facilitate effective air classification. Coarse milling (down to 100 µm) followed by air classification gave concentrates with protein contents between 54 and 59 g protein/100 g dry solids and yields up to 13%. The application of flowability aids (fused silica particles) during air classification doubled the yield of the protein-rich fraction. The air classified protein concentrate could provide a 2.3 times extended half-life of the foam compared to an intensively heated protein concentrate. In addition, the viscosity of the native concentrate was lower, while after (in vitro) digestion the amount of proteins smaller than 3 kDa was higher in native and mildly heated concentrates compared to intensively heated concentrate. These results suggest promising development of liquid-like formulations from air classified lupine protein concentrates.
    Economic values of growth and feed efficiency for fish farming in recirculating aquaculture system with density and nitrogen output limitations: a case study with African catfish (Clarias gariepinus)
    Besson, M. ; Komen, H. ; Aubin, J. ; Boer, I.J.M. de; Poelman, M. ; Quillet, E. ; Vancoillie, C. ; Vandeputte, M. ; Arendonk, J.A.M. van - \ 2014
    Journal of Animal Science 92 (2014)12. - ISSN 0021-8812 - p. 5394 - 5405.
    salmon salmo-salar - rainbow-trout - oncorhynchus-mykiss - selection - diets - weights
    In fish farming, economic values (EV) of breeding goal traits are lacking, even though they are key parameters when defining selection objectives. The aim of this study was to develop a bioeconomic model to estimate EV of 2 traits representing production performances in fish farming: the thermal growth coefficient (TGC) and the feed conversion ratio (FCR). This approach was applied to a farm producing African catfish (Clarias gariepinus) in a recirculating aquaculture system (RAS). In the RAS, 2 factors could limit production level: the nitrogen treatment capacity of the biofilter or the fish density in rearing tanks at harvest. Profit calculation includes revenue from fish sales, cost of juveniles, cost of feed, cost of waste water treatment, and fixed costs. In the reference scenario, profit was modeled to zero. EV were calculated as the difference in profit per kilogram of fish between the current population mean for both traits (µt) and the next generation of selective breeding (µt + ¿t) for either TGC or FCR. EV of TGC and FCR were calculated for three generations of hypothetical selection on either TGC or FCR (respectively 6.8% and 7.6% improvement per generation). The results show that changes in TGC and FCR can affect both the number of fish that can be stocked (number of batches per year and number of fish per batch) and the factor limiting production. The EV of TGC and FCR vary and depend on the limiting factors. When dissolved NH3-N is the limiting factor for both µt and µt + ¿t, increasing TGC decreases the number of fish that can be stocked but increases the number of batches that can be grown. As a result, profit remains constant and EVTGC is zero. Increasing FCR, however, increases the number of fish stocked and the ratio of fish produced per kilogram of feed consumed (“economic efficiency”). The EVFCR is 0.14 €/kg of fish, and profit per kilogram of fish increases by about 10%. When density is the limiting factor for both µt and µt + ¿t, the number of fish stocked per batch is fixed; therefore, extra profit is obtained by increasing either TGC, which increases the annual number of batches, or by decreasing FCR, which decreases annual feed consumption. EVTGC is 0.03 €/kg of fish and EVFCR is 0.05–0.06 €/kg of fish. These results emphasize the importance of calculating economic values in the right context to develop efficient future breeding programs in aquaculture.
    Steroids accumulate in the rearing water of commercial recirculating aquaculture systems
    Mota, V.C. ; Martins, C.I. ; Eding, E.H. ; Canário, A.V.M. ; Verreth, J.A.J. - \ 2014
    Aquacultural Engineering 62 (2014). - ISSN 0144-8609 - p. 9 - 16.
    rainbow-trout - noninvasive measurement - pleuronectes-platessa - treatment plants - atlantic salmon - free cortisol - waste-water - testosterone - fish - 17-alpha,20-beta-dihydroxy-4-pregnen-3-one
    Little information is available on steroid concentrations in the rearing water of aquaculture systems and whether they accumulate in recirculating aquaculture systems (RAS). Therefore this study aimed at determining (1) the concentrations and variation of cortisol and sex steroids in RAS, (2) the contribution of fish rearing conditions to steroid concentrations in seven commercial RAS. Each RAS was sampled twice at three different points: (1) make-up water; (2) influent and (3) effluent of the rearing unit. The results showed significant higher steroid concentrations in the influent and effluent when compared with the make-up water. On average cortisol concentration was 15.7% higher in the effluent when compared with the influent. Mean steroid concentrations in the rearing unit effluent varied between: 3.8–217.0 ng/L for cortisol, 3–12.5 ng/L for testosterone, 0.9–7.1 ng/L for 11-ketoteststerone and 1.8–12.8 ng/L for 17,20ß-dihydroxypregn-4-en-3-one. Stocking density, Total Ammonia-Nitrogen concentration and orthophosphate-P concentration (a measure of make-up water usage) showed a positive correlation with sex steroids in the water. The steroid concentrations from the present study were orders of magnitude lower than initial estimations indicating a water treatment efficiency of >99%. The results suggest that an intensification of fish production through decrease of make-up water use and increase of stocking density will lead to a build-up of steroids in the water. Although intensification is critical for the economical success of RAS, this ultimately could affect fish performance as steroids accumulates in the water of RAS at levels that can potentially be detected by some fish species.
    Lupine and rapeseed protein concentrate in fish feed: a comparative assessment of the techno-functional properties using a shear cell device and an extruder
    Draganovic, V. ; Boom, R.M. ; Jonkers, J. ; Goot, A.J. van der - \ 2014
    Journal of Food Engineering 126 (2014). - ISSN 0260-8774 - p. 178 - 189.
    trout oncorhynchus-mykiss - rainbow-trout - wheat gluten - glass-transition - kernel meal - starch - extrusion - products - moisture - quality
    The techno-functional properties of soy, lupine and rapeseed protein concentrates (SPC, LPC and RPC, respectively) in fish feed were evaluated relative to fish meal (FM). The effects were studied using a shear cell device and an extruder with emphasis on the added moisture content. Six diets were formulated: an SPC-based diet with 300 g SPC kg-1, diets containing 100 and 200 g LPC kg-1 or 100 and 200 g RPC kg-1 and an FM-based diet with 450 g FM kg-1. Each diet was extruded with an added moisture content of 29%, 25% and 22% of the mash feed rate. It was found that the technological properties of LPC closely resemble FM, being high solubility, low water-holding capacity (WHC) and low paste viscosity. The LPC 100 and 200 g kg-1 diets could be extruded at 22% moisture, which gives an extrudate with reduced drying requirements. In addition, less specific mechanical energy was needed for extrusion. In contrast, both SPC and RPC have high WHC and paste viscosity. This explains the higher feed moisture required during extrusion. The properties of the feeds containing RPC could be well within the ranges acceptable for commercial fish feed use at even higher moisture content compared with SPC. The results of the extrusion trials confirmed the observations made from the shear cell device. Thus, the shear cell device can be used to study processing conditions that are close to extrusion conditions.
    Temporal structure of sound affects behavioural recovery from noise impact in European seabass
    Neo, Y.Y. ; Seitz, J. ; Kastelein, R.A. ; Winter, H.V. ; Cate, C. ten; Slabbekoorn, H. - \ 2014
    Biological Conservation 178 (2014). - ISSN 0006-3207 - p. 65 - 73.
    zebrafish danio-rerio - seismic air-guns - dicentrarchus-labrax - fish distribution - startle response - atlantic salmon - high-intensity - rainbow-trout - teleost fish - marine fish
    Human activities in and around waters generate a substantial amount of underwater noise, which may negatively affect aquatic life including fish. In order to better predict and assess the consequences of the variety of anthropogenic sounds, it is essential to examine what sound features contribute to an impact. In this study, we tested if sounds with different temporal structure resulted in different behavioural changes in European seabass. Groups of four fish were exposed in an outdoor basin to a series of four sound treatments, which were either continuous or intermittent, with either consistent or fluctuating amplitude. The behavioural changes of the fish were analyzed by a video-tracking system. All sound treatments elicited similar behavioural changes, including startle responses, increased swimming speed, increased group cohesion and bottom diving. However, with all other sound conditions being the same, intermittent exposure resulted in significantly slower behavioural recovery to pre-exposure levels compared to continuous exposure. Our findings imply that the temporal structure of sound is highly relevant in noise impact assessments: intermittent sounds, such as from pile driving, may have a stronger behavioural impact on fish than continuous sounds, such as from drilling, even though the latter may have higher total accumulated energy. This study urges regulatory authorities and developers to pay more attention to the influence of temporal structure when assessing noise impacts. However, more studies are needed to examine other sound parameters and to determine the generality of our observations in other species and in other outdoor water bodies
    Molecular characterization of LEAP-2 cDNA in common carp (cyprinus carpio L.) and the differential expression upon a vibrio anguillarum stimulus; indications for a significant immune role in skin
    Yang Guiwen, ; Guo, H. ; Li, H. ; Shan, S. ; Zhang, X. ; Rombout, J.H.W.M. ; An, L. - \ 2014
    Fish and Shellfish Immunology 37 (2014)1. - ISSN 1050-4648 - p. 22 - 29.
    antimicrobial peptide gene - rainbow-trout - oncorhynchus-mykiss - channel catfish - bacterial challenge - hepcidin gene - nk-lysin - liver - fish - identification
    LEAP-2 is a cysteine-rich cationic antimicrobial peptide (AMP) playing an important role in host innate immune system. LEAP-2 genes have been identified from higher vertebrates and several fish species. Here we report the cloning and identification of two LEAP-2 cDNA sequences from the liver of common carp (Cyprinus carpio L.). The LEAP-2A cDNA was 1325 bp long and contained an ORF of 279 bp encoding a protein of 92 amino acids. The LEAP-2B cDNA was 608 bp long and contained an ORF of 276 bp encoding a protein of 91 amino acids. Both LEAP-2 proteins consisted of 41 amino acid residues and shared four cysteines at the conserved positions in the predicted mature peptides, highly similar to LEAP-2 of other species. Sequence alignment showed that LEAP-2 amino acid sequences were well conserved in different species, and the phylogenetic relation of LEAP-2 was coincident with evolution of biological species. Expression analysis data revealed that LEAP-2A and LEAP-2B mRNAs were expressed in a wide range of common carp tissues including liver, spleen, head kidney, skin, gills, hindgut and foregut. When injected intraperitoneally with Vibrio anguillarum, the expression level of common carp LEAP-2A was quickly up-regulated in liver, spleen, head kidney, skin, gills, foregut and hindgut, however, the expression level of LEAP-2B was similarly up-regulated in spleen, skin, gills and hindgut but not in liver, head kidney and foregut. Our results showed that the LEAP-2A had a markedly high constitutive expression in skin, and the LEAP-2A and the LEAP-2B had a significantly high up-regulated expression after stimulus in skin. This differential expression of LEAP-2 in common carp suggests that it may play a key role in immune responses against invading pathogens and both LEAP-2 molecules may be involved in mucosal immunity.
    Dietary carbohydrate composition can change waste production and biofilter load in recirculating aquaculture systems
    Meriac, A. ; Eding, E.H. ; Schrama, J.W. ; Kamstra, A. ; Verreth, J.A.J. - \ 2014
    Aquaculture 420-421 (2014)15 January 2014. - ISSN 0044-8486 - p. 254 - 261.
    trout oncorhynchus-mykiss - single-sludge denitrification - oreochromis-niloticus l. - rainbow-trout - fish-meal - nile tilapia - nonstarch polysaccharides - salmonid aquaculture - growth-performance - effluent treatment
    This study investigated the effect of dietary carbohydrate composition on the production, recovery and degradability of fecal waste from rainbow trout (Oncorhynchus mykiss) in recirculating aquaculture systems (RAS). Dietary carbohydrate composition was altered by substituting starch with non-starch polysaccharides (NSP) while keeping the diets isonitrogenous and isoenergetic. We tested a high starch, low NSP (LNSP) and a low starch, high NSP (HNSP) diet in six identical, small-scale RAS (V = 460 L). Each diet was tested in three independent systems over a period of six weeks. Shifting dietary carbohydrates from starch to NSPs resulted in a 50% increase in the production of chemical oxygen demand (COD) based on digestibility. Fecal waste recovery showed a 40% increase in HNSP treatments when compared with LNSP. Consequently, the COD output from HNSP systems doubled from 91 g to 194 g of COD per kg feed when compared with LNSP. Although COD production was higher in HNSP systems, the COD load on the biofilters was significantly lower when compared with LNSP systems. COD-to-nitrogen (COD/N) ratios in the biofilter load were 1.7 ± 0.2 and 2.2 ± 0.2 g COD/g N for HNSP and LNSP, respectively. Shifting the dietary carbohydrate composition from starch to NSPs decreased the biodegradability of fecal COD from 66.3% to 43.7% (P <0.001). Fiber analyses revealed that approximately 40% of the COD in HNSP feces came from cellulose and hemicellulose. The increased COD production of HNSP diets could be exploited by using fecal COD as an internal carbon source in denitrification. Full denitrification would be theoretically possible with a measured COD/N ratio of 7.2 in the waste stream of HNSP systems. However, it is not clear if the low COD bioavailability of HNSP feces could be a limiting factor. This study shows that COD/N ratios in the biofilter load and system output can be manipulated by changing dietary carbohydrate composition. Although an increased dietary NSP content increased COD production, it also increased COD recovery, decreased COD load on the biofilters and generated sufficient carbon for denitrification on internal sources.
    The impact of elevated water ammonia and nitrate concentrations on physiology, growth and feed intake of pikeperch (Sander lucioperca)
    Schram, E. ; Roques, J.A.C. ; Kuijk, T. van; Abbink, W. ; Heul, J.W. van der; Vries, P. de; Bierman, S.M. ; Vis, J.W. van de; Flik, G. - \ 2014
    Aquaculture 420-421 (2014). - ISSN 0044-8486 - p. 95 - 104.
    trout oncorhynchus-mykiss - acid-base regulation - early-life stages - rainbow-trout - salmo-gairdneri - recirculating aquaculture - scophthalmus-maximus - clarias-gariepinus - chronic toxicity - aquatic animals
    The ammonia (NH3) and nitrate (NO3-) threshold concentrations in rearing water of juvenile pikeperch (Sander lucioperca) were assessed. Pikeperch with an initial mean (SD) weight of 17.7 (4.2) g were exposed to 0.9 (control), 3.6, 5.2, 7.1, 11.2 and 18.9 µM NH3 in the water for 42 days. Plasma NH4+ concentrations stayed at control levels (~ 650 µM) up to 11.2 µM NH3 in the water. At the highest water NH3 concentration tested, plasma NH4+ had more than doubled to 1400 µM. Based on the specific growth rate, the EC10 value for NH3 was 5.7 µM. When pikeperch (initial mean (SD) weight of 27.0 (4.9) g) were exposed to 0.1 (control), 1.5, 2.3, 3.7, 6.1, 10.2, 15.8 and 25.6 mM NO3- for 42 days, mean (SD) plasma NO3- concentrations increased linearly from 88 (47) to 5993 (899) µM at the highest ambient NO3- level. Feed intake, specific growth rate and feed conversion ratio were not affected. Neither NH3 nor NO3- exposure significantly affected haematocrit, plasma concentrations of cortisol, glucose, lactate, osmolality, gill morphology or branchial Na+/K+-ATPase activity in pikeperch. For juvenile pikeperch we advise not to exceed a water NH3 concentration of 3.4 µM (0.05 mg NH3–N/L), the lower limit of the 95% confidence interval of the EC10 value for SGR, to ensure proper physiology and growth. For NO3- we advise not to exceed 25 mM (350 mg NO3-–N/L). This criterion is based on the highest NO3- concentration tested (25.6 mM). As no negative effects were detected at the highest concentration tested, the actual NO3- threshold probably exceeds 25.6 mM.
    High corticosterone and sex reversal in common carp (Cyprinus carpio L.) with adrenal hyperplasia caused by P450c17a2 deficiency
    Nematollahi, M.A. ; Pelt-Heerschap, H.M.L. van; Komen, H. - \ 2014
    Aquaculture 418-419 (2014). - ISSN 0044-8486 - p. 165 - 170.
    teleost fish - 21-hydroxylase deficiency - interrenal hyperplasia - recessive mutation - cortisol response - determining gene - oryzias-latipes - stress-response - rainbow-trout - expression
    The aim of this study was to investigate the inheritance of adrenal hyperplasia, caused by 17a-hydroxylase deficiency, and its association with female to male sex reversal in common carp. Inbred strains used in this experiment were E4 (XX, female, normal), E5 (XX, male, adrenal hyperplasia) and E7 (XX, male, adrenal hyperplasia). F1 females (E4E5: XX, normal) were crossed to E5 and E7 males to produce backcross progeny (BC5 and BC7), or reproduced by gynogenesis to produce doubled haploid progeny (DH). Fish (age 6 months) were subjected to a net confinement stressor and sacrificed to collect blood plasma for analysis of cortisol and corticosterone, and to determine sex. Values for plasma corticosterone showed a clear segregation pattern, consistent with a single recessive gene model. There was a highly significant difference between high and low corticosterone responders in BC and DH progeny groups. Mean corticosterone values for high corticosterone responders in the three groups BC5, BC7 and DH were, respectively: 1706, 1760 and 1366 ng/ml. For low corticosterone responders values were 1.5, 1.1 and 0.6 ng/ml. High corticosterone responders had on average low levels of cortisol: 21.3, 24 and 17.3 ng/ml for BC5, BC7 and DH. Low corticosterone responders had normal levels (66.7, 105.1 and 65.2 ng/ml for BC5, BC7 and DH, respectively). Sex ratios were significantly different between high and low corticosterone responders. High corticosterone responders were predominantly male, while low corticosterone responders were female or intersex. High corticosterone responders had well developed testis and were fertile indicating that in the gonads, 17a-hydroxylase is not impaired. The observed effect on sex shows that 17a-hydroxylase deficiency most likely augments sex reversal in common carp, either directly through high levels of plasma corticosterone, or through paracrine effects of elevated ACTH production.
    Stress in African catfish (clarias gariepinus) following overland transportation
    Manuel, R. ; Boerrigter, J. ; Roques, J. ; Heul, J.W. van der; Bos, R. van den; Flik, G. ; Vis, J.W. van de - \ 2014
    Fish Physiology and Biochemistry 40 (2014)1. - ISSN 0920-1742 - p. 33 - 44.
    oncorhynchus-mykiss walbaum - carp cyprinus-carpio - common carp - animal-welfare - rainbow-trout - responses - fish - l. - temperature - aggression
    Of the many stressors in aquaculture, transportation of fish has remained poorly studied. The objective of this study was therefore to assess the effects of a (simulated) commercial transportation on stress physiology of market-size African catfish (Clarias gariepinus). Catfish weighing approximately 1.25 kg were returned to the farm after 3 h of truck-transportation, and stress-related parameters were measured for up to 72 h following return. Recovery from transportation was assessed through blood samples measuring plasma cortisol, glucose and non-esterified fatty acids (NEFA) and gill histology. Also, the number of skin lesions was compared before and after transport. Pre-transport handling and sorting elevated plasma cortisol levels compared to unhandled animals (before fasting). Plasma cortisol levels were further increased due to transportation. In control fish, plasma cortisol levels returned to baseline values within 6 h, whereas it took 48 h to reach baseline values in transported catfish. Plasma glucose and NEFA levels remained stable and were similar across all groups. Transported catfish did not, on average, have more skin lesions than the handling group, but the number of skin lesions had increased compared to unhandled animals. The macroscopic condition of the gills was similar in control, transported and unhandled catfish; however, light microscopy and immunohistochemistry revealed atypical morphology and chloride cell migration normally associated with adverse water conditions. From our data, we conclude that transportation may be considered a strong stressor to catfish that may add to other stressors and thus inflict upon the welfare of the fish.
    The impact of elevated water nitrate concentration on physiology, growth and feed intake of African catfish Clarias gariepinus (Burchell 1822)
    Schram, E. ; Roques, J.A.C. ; Abbink, W. ; Vries, P. de; Bierman, S.M. ; Vis, J.W. van de - \ 2014
    Aquaculture Research 45 (2014)9. - ISSN 1355-557X - p. 1499 - 1511.
    acid-base-balance - rainbow-trout - fresh-water - oxygen-affinity - astacus-astacus - channel catfish - na+/k+-atpase - nitrite - transport - toxicity
    The nitrate threshold concentration in rearing water of African catfish (Clarias gariepinus) was assessed. Female African catfish with an initial mean (SD) weight of 154.3 (7.5) g were exposed to 0.4 (Control), 1.5, 4.2, 9.7 and 27.0 mM nitrate for 42 days. Mean (SD) plasma concentrations of nitrate increased from 71 (29) to 6623 (921) µM at the highest ambient nitrate level. Mean (SD) plasma nitrite concentration ranged from 1.2 (0.5) to 7.9 (9.0) µM. Haematocrit, plasma concentrations of non-esterified fatty acids (NEFA), cortisol, glucose, lactate, osmolality, gill morphology and branchial Na+/K+-ATPase activity were not affected. Feed intake and specific growth rate were significantly reduced at the highest nitrate concentration. We advise not to exceed a water nitrate concentration of 10 mM (140 mg L-1 NO3-N) to prevent the risk of reduced growth and feed intake in African catfish aquaculture.
    Genetic parameters for reproductive traits in female Nile tilapia (Oreochromis niloticus): II. Fecundity and fertility
    Trong, T.Q. ; Arendonk, J.A.M. van; Komen, J. - \ 2013
    Aquaculture 416-417 (2013). - ISSN 0044-8486 - p. 72 - 77.
    rainbow-trout - selection responses - body measurements - fillet traits - 6 generations - brown trout - growth - improvement - heritability - weight
    Harvest weight is the main trait in Nile tilapia (Oreochromis niloticus) breeding programmes. The effects of selection for harvest weight on female reproductive traits are unknown. In this paper we estimate genetic parameters for reproductive traits and their correlation with harvest weight using females from the generation 12 of the GIFT strain of Nile tilapia in the Mekong Delta of Viet Nam. Spawning records were obtained from single pair mating as well as group mating experiments. The traits were categorised into two groups: fecundity-related traits and fertility-related traits. Fecundity traits were: number of eggs (NEGG), relative fecundity as the ratio of number of eggs to female spawning weight (RFEC), egg weight (EGGW) and egg diameter (EGGD); fertility traits were: number of fertilised eggs (FEGG), number of hatched eggs (HAT), number of swim-up fry (SWUP), and fertilisation rate (FER, in %). Heritability estimates for fecundity traits were low, ranging from 0.05 to 0.08. Heritability estimates for fertility traits were also low, ranging from 0.06 to 0.12. Genetic correlations for HW with NEGG and TEGGW were positive (0.51 and 0.42, respectively), while correlations for HW with RFEC, EGGW, and EGGD were negative (- 0.72, - 0.48, and - 0.50, respectively). The same trend was observed for body weight at spawning (SPW), but genetic correlations between SPW and fecundity traits were higher than those between HW and fecundity traits. Genetic correlations between HW and fertility traits were all moderate to high (0.46 to 0.69), except for FER (0.15 ± 0.24). Genetic correlations between SPW and fertility traits were even higher (0.69 to 0.93). We conclude that both HW and SPW have favourable genetic correlations with NEGG, RFEC, and SWUP, which are the desired characteristics for Nile tilapia seed production. Selection for HW does not affect these traits. However, Nile tilapia females selected for large HW tend to produce smaller eggs. We recommend monitoring the phenotypic and/or genetic trend in this trait, as smaller eggs might, on the longer term, lead to lower fry survival.
    Comparative study of B-glucan induced respiratory burst measured by nitroblue tetrazolium assay and real-time luminol-enhanced chemiluminescence assay in common carp (Cyrpinus carpio L.)
    Vera-Jimenez, N.I. ; Pietretti, D. ; Wiegertjes, G.F. ; Nielsen, M.E. - \ 2013
    Fish and Shellfish Immunology 34 (2013)5. - ISSN 1050-4648 - p. 1216 - 1222.
    head-kidney leukocytes - hydrogen-peroxide production - trout oncorhynchus-mykiss - diluted whole-blood - rainbow-trout - innate immunity - in-vitro - polymorphonuclear leukocytes - aeromonas-hydrophila - parasite infections
    The respiratory burst is an important feature of the immune system. The increase in cellular oxygen uptake that marks the initiation of the respiratory burst is followed by the production of reactive oxygen species (ROS) such as superoxide anion and hydrogen peroxide which plays a role in the clearance of pathogens and tissue regeneration processes. Therefore, the respiratory burst and associated ROS constitute important indicators of fish health status. This paper compares two methods for quantitation of ROS produced during the respiratory burst in common carp: the widely used, single-point measurement based on the intracellular reduction of nitroblue tetrazolium (NBT) and a real-time luminol-enhanced assay based on the detection of native chemiluminescence. Both assays allowed for detection of dose-dependent changes in magnitude of the respiratory burst response induced by ß-glucans in head kidney cells of carp. However, whereas the NBT assay was shown to detect the production of only superoxide anions, the real-time luminol-enhanced assay could detect the production of both superoxide anions and hydrogen peroxide. Only the chemiluminescence assay could reliably record the production of ROS on a real-time scale at frequent and continual time intervals for time course experiments, providing more detailed information on the respiratory burst response. The real-time chemiluminescence assay was used to measure respiratory burst activity in macrophage and neutrophilic granulocyte-enriched head kidney cell fractions and total head kidney cell suspensions and proved to be a fast, reliable, automated multiwell microplate assay to quantitate fish health status modulated by ß-glucans.
    Oxidative and nitric oxide responses in carp macrophages induced by zymosan, MacroGard and selective dectin-1 agonists suggest recognition by multiple pattern recognition receptors
    Pietretti, D. ; Vera-Jimenez, N.I. ; Hoole, D. ; Wiegertjes, G.F. - \ 2013
    Fish and Shellfish Immunology 35 (2013)3. - ISSN 1050-4648 - p. 847 - 857.
    zebrafish danio-rerio - beta-glucan receptor - polymeric immunoglobulin receptor - cyprinus-carpio - atlantic salmon - rainbow-trout - differential expression - dietary beta-1,3-glucan - aeromonas-hydrophila - scavenger receptors
    ß-Glucans are glucose polymers that are found in the cell walls of plants, bacteria, certain fungi, mushrooms and the cell wall of baker's yeast. In mammals, myeloid cells express several receptors capable of recognizing ß-glucans, with the C-type lectin receptor dectin-1 in conjunction with Toll-like receptor 2 (TLR2), considered key receptors for recognition of ß-glucan. In our studies to determine the possible involvement of these receptors on carp macrophages a range of sources of ß-glucans were utilized including particulate ß-glucan preparations of baker's yeast such as zymosan, which is composed of insoluble ß-glucan and mannan, and MacroGard(®), a ß-glucan-based feed ingredient for farmed animals including several fish species. Both preparations were confirmed TLR2 ligands by measuring activation of HEK293 cells transfected with human TLR2 and CD14, co-transfected with a secreted embryonic alkaline phosphatase (SEAP) reporter gene. In addition, dectin-1-specific ligands in mammals i.e. zymosan treated to deplete the TLR-stimulating properties and curdlan, were monitored for their effects on carp macrophages by measuring reactive oxygen and nitrogen radicals production, as well as cytokine gene expression by real-time PCR. Results clearly show the ability of carp macrophages to strongly react to particulate ß-glucans with an increase in the production of reactive oxygen and nitrogen radicals and an increase in cytokine gene expression, in particular il-1ß, il-6 and il-11. We identified carp il-6, that was previously unknown. In addition, carp macrophages are less, but not unresponsive to selective dectin-1 agonists, suggesting recognition of ß-glucans by multiple pattern recognition receptors that could include TLR but also non-TLR receptors. Candidate receptors for recognition of ß-glucans are discussed.
    A history of fish vaccination. Science-based disease prevention in aquaculture
    Gudding, R. ; Muiswinkel, W.B. van - \ 2013
    Fish and Shellfish Immunology 35 (2013)6. - ISSN 1050-4648 - p. 1683 - 1688.
    rainbow-trout - vibrio-anguillarum - maternal immunity - oral immunization - yersinia-ruckeri - direct immersion - salmo-gairdneri - vaccines - salmonicida - fry
    Disease prevention and control are crucial in order to maintain a sustainable aquaculture, both economically and environmentally. Prophylactic measures based on stimulation of the immune system of the fish have been an effective measure for achieving this goal. Immunoprophylaxis has become an important part in the successful development of the fish-farming industry. The first vaccine for aquaculture, a vaccine for prevention of yersiniosis in salmonid fish, was licensed in USA in 1976. Since then the use of vaccines has expanded to new countries and new species simultaneous with the growth of the aquaculture industry. This paper gives an overview of the achievements in fish vaccinology with particular emphasis on immunoprophylaxis as a practical tool for a successful development of bioproduction of aquatic animals.
    Wheat gluten in extruded fish feed: Effects on morphology and on physical and functional properties
    Draganovic, V. ; Goot, A.J. van der; Boom, R.M. ; Jonkers, J. - \ 2013
    Aquaculture Nutrition 19 (2013)6. - ISSN 1353-5773 - p. 845 - 859.
    structural characteristics - lysine supplementation - salmonid feeds - rainbow-trout - oil uptake - products - protein - meal - microstructure - digestibility
    This article focuses on understanding the role of vital wheat gluten on the structural parameters of extruded fish feed and its correlation to the physical and functional properties. Gluten–soy protein concentrate blends with five gluten concentrations (0–200 g kg-1) were produced. An abrupt reduction in oil uptake was observed with the 200 g gluten kg-1 blend. Inclusion of gluten from 100 to 200 g kg-1 resulted in unacceptable product properties. Sinking of feed pellets with 0 and 50 g gluten kg-1 was 100%, whereas only 36% of pellets with 200 g gluten kg-1 sank. We suspect that this is due to a relationship between morphological structure and oil impregnation during coating of feeds. The addition of gluten at 200 g kg-1 gave a smoother and non-porous outer surface. Pellets without gluten had a larger number of cells that were smaller than 200 µm (P <0.05) compared with pellets with 100 and 200 g gluten kg-1. More spherical cell shapes (P <0.01) and a compact structure were favoured in the presence of gluten. The closed porosity increased (P <0.05), whereas interconnectivity between pores decreased (P <0.01), with increasing gluten content from 0 to 200 g kg-1. The effects of the addition of gluten are probably related to the film-forming properties of gluten.
    Genotype by environment interaction for growth of sole (Solea solea) reared in an intensive aquaculture system and in a semi-natural environment
    Mas-Munoz, J. ; Blonk, R.J.W. ; Schrama, J.W. ; Arendonk, J.A.M. van; Komen, H. - \ 2013
    Aquaculture 410-411 (2013). - ISSN 0044-8486 - p. 230 - 235.
    bass dicentrarchus-labrax - trout oncorhynchus-mykiss - rainbow-trout - common sole - body-weight - genetic correlations - rearing conditions - molecular markers - dover sole - heritability
    The objective of the current study was to assess the extent of genotype by environment interaction for growth of sole (Solea solea) grown in an intensive recirculation aquaculture system (RAS) and in a semi-natural outdoor pond (POND). The RAS environment consisted of four indoor shallow raceways without sand, where fish were stocked at a density of 40 fish/m2 and fed with dry pelleted feed. The POND environment consisted of one 100 m2 outdoor pond, where fish were stocked at densities of 1.4 fish/m2, and fish could prey on live ragworms present in the sediment. S. solea (n = 2800) offspring, produced by natural mating of wild broodstock, and with initial body weight of 64 ± 20 g, were randomly divided over the two environments. After a growing period of 165 days, all fish were harvested and harvest weight (HW, g), specific growth rate (SGR, %BW/d) and sex of all fish was assessed; molecular relatedness between animals was estimated using 9 microsatellite markers. In POND 980 fish and in RAS 774 fish were successfully genotyped and used in the analysis. SGR was higher for sole reared in POND compared to RAS (0.60 ± 0.01 vs. 0.57 ± 0.01). Pearson correlation of initial body weight with SGR was negative, and more so in POND compared to RAS (- 0.30 vs. - 0.16, respectively). Genetic variance and heritability estimates for SGR were higher in POND (h2 = 0.20 ± 0.05) than in RAS (h2 = 0.04 ± 0.02). Genetic correlations for HW and SGR of sole reared in RAS and in POND were 0.56 ± 0.34 and 0.27 ± 0.3, respectively. The differences in heritable variation and the low genetic correlations of growth of sole between environments suggest strong genotype by environment interaction. These results are important in developing breeding programs for sole because the accuracy of selection and genetic gain for growth of sole may differ between environments. Low genetic correlations for growth between environments imply that the best genotypes in an intensive aquaculture environment are not to be necessarily the best genotypes in more natural environments such as ponds.
    Oxygen Consumption Constrains Food Intake in Fish Fed Diets Varying in Essential Amino Acid Composition
    Subramanian, S. ; Geurden, I. ; Figueiredo-Silva, A.C. ; Nusantoro, S. ; Kaushik, S.J. ; Verreth, J.A.J. ; Schrama, J.W. - \ 2013
    PLoS ONE 8 (2013)8. - ISSN 1932-6203 - 7 p.
    trout oncorhynchus-mykiss - european sea bass - rainbow-trout - dissolved-oxygen - nile tilapia - feed-intake - oreochromis-niloticus - salmo-gairdneri - self-selection - protein
    Compromisation of food intake when confronted with diets deficient in essential amino acids is a common response of fish and other animals, but the underlying physiological factors are poorly understood. We hypothesize that oxygen consumption of fish is a possible physiological factor constraining food intake. To verify, we assessed the food intake and oxygen consumption of rainbow trout fed to satiation with diets which differed in essential amino acid (methionine and lysine) compositions: a balanced vs. an imbalanced amino acid diet. Both diets were tested at two water oxygen levels: hypoxia vs. normoxia. Trout consumed 29% less food under hypoxia compared to normoxia (p0.05). This difference in food intake between diets under normoxia together with the identical oxygen consumption supports the hypothesis that food intake in fish can be constrained by a set-point value of oxygen consumption, as seen here on a six-week time scale.
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