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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    The evaluation of energy in fish feed
    Haidar, Mahmoud - \ 2017
    Wageningen University. Promotor(en): J.A.J. Verreth, co-promotor(en): J.W. Schrama. - Wageningen : Wageningen University - ISBN 9789463438049 - 155
    oreochromis niloticus - fish feeding - feed formulation - digestible energy - dietary protein - dietary fat - carbohydrates - growth - feed evaluation - fish culture - aquaculture - oreochromis niloticus - visvoeding - voersamenstelling - verteerbare energie - voedingseiwit - voedingsvet - koolhydraten - groei - voederwaardering - visteelt - aquacultuur

    New and alternative plant ingredients are increasingly incorporated in fish feed due to the scarcity of captured fish and increased fishmeal and fish oil prices. As a result, current fish feeds are characterized by a highly variable ingredients composition, leading to a similar variability in the dietary macronutrients composition, especially the carbohydrates fraction. Appropriate formulation of the energy component in fish feeds requires information on nutrient digestibility, energy requirements for maintenance, and the efficiency of utilization of digestible energy for growth (kgDE). In fish feed formulation, the energy evaluation is based on digestible energy (DE) basis. The main assumptions of this DE system are that maintenance requirements and kgDE are independent of dietary factors. The main objective of this thesis was to evaluate and improve the DE system for Nile tilapia. Data showed that, opposite to what is assumed in literature and irrespective of the feeding level applied, an optimal digestible protein to digestible energy ratio (DP/DE) for young Nile tilapia could not be detected. In addition, it was expected that Nile tilapia would show a maximal protein deposition in relation to a wide range of DP/DE ratios, however, this was either observed. Further investigations showed that different body compartments/organs responded differently in terms of protein and fat composition as a result of changes in the dietary DP/DE ratio. In tilapia, viscera and the “rest” fraction (head, skin, fins and bones) were the main site for fat retention. In addition, protein content of fillets seems to be constant (about 17%) and not affected by dietary factors in Nile tilapia. In addition, the effect of using new plant ingredients in Nile tilapia diets was also investigated. The results showed that the ingredients composition had an effect on the maintenance requirements of Nile tilapia. Further, changes in the ratio of starch vs non starch carbohydrates revealed that energy retention was lower when more dietary fibers were included. In addition, the net energy retention differed also when the levels of digestible protein, fat and carbohydrates changed in the diets. The latter results proved that kgDE was not constant and was dependent on diet composition. All aforementioned results led us to calculate the energetic efficiencies of digestible protein, fat and carbohydrates for net energy retention. These estimated efficiencies were used to propose a net energy evaluation system being feasible for Nile tilapia.

    The development of a sole diet based on the composition of ragworm
    Kals, Jeroen - \ 2017
    Wageningen University. Promotor(en): J.A.J. Verreth, co-promotor(en): J.W. Schrama; R.J.W. Blonk. - Wageningen : Wageningen University - ISBN 9789463431804 - 136
    dover soles - annelida - fish feeding - anaemia - haemoglobin - fish culture - aquaculture - tong (vis) - annelida - visvoeding - anemie - hemoglobine - visteelt - aquacultuur

    Scientifically, this study aimed to validate the potential of ragworm to alleviate anaemia in common sole and to identify the dietary requirements of common sole to alleviate this anaemia. At the same time it was aimed to explain part of the difference in growth between sole fed a commercial pellet and sole fed ragworm. Practically, this study aimed to develop a diet that achieves similar growth rates in sole as when fed ragworm. Sole fed commercial pellets developed nutritional anaemia. Feeding ragworm or mussel alleviates this nutritional anaemia. It is suggested that the ability of mussel or ragworm (meal) to alleviate anaemia and improve growth in sole can be explained by heme iron and high B12 levels. Yet, iron absorption in sole is high and independent of iron source. Still, heme increases the absorption of copper. The high absorption of iron and copper in sole fed heme does not affect the haematocrit (Hct) and haemoglobin (Hb) levels, which indicates the anaemia in sole is not an iron or a copper deficiency anaemia. The Hct and Hb levels in sole are affected by dietary B12. Yet, the applied levels are unable to alleviate the anaemia in sole induced by feeding commercial pellets. More options to alleviate the nutritional anaemia in common sole are discussed. Nutrients as vitamin C, B1, B2, B5 and a possible role of dietary EPO are discussed. It is suggested that the slow growth of pellet-fed sole might be due to the low Hct and Hb levels, which hampers the uptake of oxygen, and thus also the overall metabolic capacity, including the scope for growth. Discussed is a 7°C difference in the “optimal” temperature between sole fed ragworm and the 2nd generation pellet and that the “worm effect” is dependent on temperature. However, the growth rate of sole fed the 3rd generation pellet at 18.4°C was comparable to the growth rate of sole fed ragworm, which could not have been the consequence of increasing Hct and Hb levels as these were comparable to levels found in sole fed commercial pellets. Yet, B12 levels in blood plasma of sole are up to 200 times those of other (fish) species. Hence, we inferred on the possibility of a specific metabolic function of B12 in respiration in sole. In addition, the economic and practical impact of the improved growth rate in sole culture is discussed. Finally, several suggestions for future research are given.

    Feeds, water quality, gut morphology and digestion in Nile tilapia (Oreochromis niloticus)
    Trần Ngọc Thiên Kim, Kim - \ 2017
    Wageningen University. Promotor(en): J.A.J. Verreth, co-promotor(en): J.W. Schrama; Arjen J. Roem. - Wageningen : Wageningen University - ISBN 9789463431484 - 127
    tilapia - oreochromis niloticus - feeds - fish feeding - water quality - digestion - digestibility - intestines - morphology - fish culture - aquaculture - tilapia - oreochromis niloticus - voer - visvoeding - waterkwaliteit - spijsvertering - verteerbaarheid - darmen - morfologie - visteelt - aquacultuur

    Diet composition, ingredient and nutrients, are important to consider for maintaining intestinal functions. Studies on both positive (using feed additives) and negative effects (using high inclusion of plant ingredients) of fish feeds are numerous, however, between studies results are often highly variable, both in type of response and in significance. The central hypothesis of this study was that adverse environmental conditions may aggravate negative effects of plant ingredients on the intestinal functions to the extent that mild effects become severe and perceptible. To do so, dietary factors and environmental conditions were evaluated and the interaction between diet composition and environmental conditions were studied in Nile tilapia.

    In Chapter 2, six common raw materials including hydrolysed feather meal (HFM), soybean meal (SBM), rice bran (RB), rapeseed meal (RM), sunflower meal (SFM) and dried distiller grains with solubles (DDGS) were chosen to determine the effect of nutrient digestibility, nitrogen/energy balance and changes in intestinal morphology. The study demonstrated that feed ingredients do have an impact on the alteration in intestinal parameters, but also on the nutrient digestibility and the nitrogen/energy balance. Although being well digested, soybean meal caused the most obvious alteration in the intestinal morphology. These alterations were not related to the nutrient digestibility nor to nitrogen/energy balance parameters. Soybean meal, causing the most alterations in the intestinal morphology, was further used in all subsequent chapters of this thesis.

    Chapter 3 and 4 described the interaction between diet composition and environmental conditions on the intestinal functions. This was studied with two different environmental conditions, dissolved oxygen (Chapter 3) and salinity (Chapter 4). These two chapters evaluated whether suboptimal environmental conditions (low dissolved oxygen or elevated salinity in water) may interact with a soybean meal based diet in nutrient digestion and intestinal morphology of tilapia. The study demonstrated that environmental stressors can aggravate/reveal the negative intestinal morphology changes induced by a soybean meal based diet. However, these effects of adverse environmental conditions on the intestinal functions were not homogenously dispersed over the whole intestinal length. The effect of salinity on the intestinal morphology occurred predominantly in the distal intestine, whereas the effect of low oxygen concentration was more visible at the proximal intestine. Alterations in the intestinal morphology, as found in this study, have wider effects on the performance of the affected fish. In Chapter 3, the protein digestibility decreased under hypoxic conditions at week 8, which parallels with the time related alteration in intestinal morphology. Chapter 4 showed that when fish were raised at 15 ‰ salinity, nutrient digestibility increased; however, this positive effect decreased when the intestinal morphology changed. The study also found that the combined effect of a soybean meal based diet and hypoxia was stronger compared to the combination with elevated salinity. Therefore, the combination with hypoxia was further used in the next study of this thesis.

    In Chapter 5, the combination of hypoxic condition and a soybean meal based diet was chosen to test the hypothesis that only under stressful conditions, the effects of feed additives can be noticed. The impact of two dietary organic acids, formic acid and butyric acid, on nutrient digestibility and intestinal morphology was determined under optimal (normoxia) and suboptimal conditions (hypoxia). The results showed that although organic acids did not significantly improve growth performance and nutrient digestibility under normoxic condition, they did so under hypoxic conditions. Fish fed organic acid supplemented diets all showed improvements in the morphology of intestine under normoxic conditions, and these effects were more enhanced under hypoxic conditions. This indicates that environmental conditions can alter the effect of organic acid on nutrient digestibility and intestinal morphology in tilapia.

    Finally, Chapter 6 provided a synthesis of the main findings, and a reflection on the methodologies used in Chapters 2-5 as well as a discussion on the relevance of this study to aquaculture. It is concluded that although being well digested, soybean meal caused the most obvious alteration in intestinal morphology. The adverse environmental conditions aggravated negative effects of soybean meal based diets on the intestinal functions to the extent that mild effects become severe and visible. The negative effect on intestinal morphology of soybean meal in the diet is enhanced at low oxygen level and at elevated salinity. The effect of salinity on the intestinal morphology occurs predominantly in the distal intestine, whereas the effect of low oxygen concentration is more visible at the proximal intestine. The thesis indicated that the impact of organic acids on intestinal functions is dependent on environmental conditions, being more pronounced under challenging conditions (e.g. hypoxia). Therefore, studies on both positive (using feed additives) and negative effects (using high inclusion of plant ingredients) of dietary factors should be done under suboptimal conditions.

    Microbial interactions in the fish gut
    Giatsis, Christos - \ 2016
    Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Marc Verdegem; Detmer Sipkema. - Wageningen : Wageningen University - ISBN 9789462578777 - 196
    fishes - tilapia - larvae - microbial interactions - intestinal microorganisms - intestines - dynamics - fish feeding - probiotics - fish culture - aquaculture - vissen - tilapia - larven - microbiële interacties - darmmicro-organismen - darmen - dynamica - visvoeding - probiotica - visteelt - aquacultuur

    Aquaculture has realized considerable growth over the past years while the world demand on seafood has been increasing. As aquaculture intensifies, the production sector needs to tackle major bottlenecks such as suboptimal growth and high and unpredictable mortality, especially in larval cultures. Fish-microbe interactions are closely related to overall fish health. To obtain a healthy and resilient microbial community (MC), it is important to understand the underlying mechanisms of microbial colonization in the fish gut.

    The goal of this thesis was to investigate the role of water and feed microbial communities on shaping gut communities during early development of Nile tilapia.

    To determine the contribution of stochasticity to overall variation, we first characterized the spatio-temporal variation in MC composition between individuals reared within the same or in replicate recirculating or active suspension systems (RAS vs. AS). Highly similar MCs developed in the gut when larvae shared the same water and diet. Rearing larvae in replicate production systems resulted in significantly different gut communities indicating that compositional replication of the MCs of an ecosystem is not fully predictable. We found that mainly water MCs, and to a lesser degree feed MCs, were associated with changes in MCs. Thus, we could conclude that steering gut MCs can be possible through water MC management tailored on the specifications of the rearing system in use.

    Next, the possibility of early life steering of gut communities via microbial manipulations of feed MCs was explored. We hypothesized that gut microbial composition is strongly shaped by selective pressures in the gut and by the MCs present in the water. Thus similar MCs should develop between treatments regardless of the dietary treatments. Fish larvae were fed either a control feed or the control feed containing MCs derived from aerobic, methanogenic or denitrifying sludge reactors. We found that gut microbiota shared a much higher number of operational taxonomic units (OTUs) with microbiota in sludge-based feeds than with water, resulting in distinct gut MCs between treatments. Our findings suggest that Nile tilapia gut MC has a certain plasticity, which makes it amenable to interventions through proper feed microbial management.

    Subsequently, we tested the imprinting effect of early exposure to the probiotic Bacillus subtilis on shaping gut MC composition even after the administration of the probiotic discontinues. For this, we constrained the initial contact with microbes from the environment by producing axenic tilapia larvae, which were then exposed to normal husbandry conditions. Early life probiotic exposure affected gut MC composition during B. subtilis administration but also within the first two weeks after its administration stopped, thus indicating that early exposure to the probiotic strain via the water had a sustained impact on gut MC composition.

    Finally, overall conclusions and practical implications of our results for aquaculture production were presented. A meta-analysis was also performed to examine (1) the phylogenetic similarity among gut MCs of the same and different fish species reared in different habitats, fed different diets and at different developmental stages and (2) the factors primarily shaping gut MCs. We showed that the selective pressure responsible in shaping gut MC composition highly depends on the host as gut communities clustered primarily together by host and to a lesser extent reflected differences in habitat and diet. The phylogenetic analysis of gut communities revealed a clear clustering by study thus indicating that manipulation of gut communities is conceivable. Study-to-study variation could be attributed to the methodology used for MC analysis highlighting also the importance of methodological uniformity when comparisons between studies are made.

    Overall, this thesis provided fundamental knowledge on MC composition and development in aquaculture rearing systems. Although the insights generated by this thesis are still premature to fully explain, predict or steer MC composition, and though additional studies are needed, we believe that, in the long run, this approach will facilitate the development of safe and effective methods for manipulating gut microbial composition to promote fish health in aquaculture rearing systems.

    IAG ring test animal proteins 2016
    Raamsdonk, L.W.D. van; Rhee, N.E. van de; Scholtens-Toma, I.M.J. ; Prins, T.W. ; Vliege, J.J.M. ; Pinckaers, V.G.Z. - \ 2016
    Wageningen : RIKILT Wageningen UR (RIKILT report 2016.008) - 31
    ring test - animal proteins - analytical methods - microscopy - fish feeding - animal health - polymerase chain reaction - ringtest - dierlijke eiwitten - analytische methoden - microscopie - visvoeding - diergezondheid - polymerase-kettingreactie
    The annual ring test for the detection of animal proteins in animal feed of the IAG - International Association for Feeding stuff Analysis, Section Feeding stuff Microscopy was organized by RIKILT - Wageningen UR, The Netherlands. The aim of the ring study was to provide the participants information on the performance of the local implementation of the detection method for their local quality systems. A further aim was to gather information about the application of the microscopic method. The current 2016 version of the IAG ring test for animal proteins facilitated the full scenario with the methods for microscopy and PCR as published in Regulation (EC) 51/2013 amending Annex VI of Regulation (EC) 152/2009 together with accompanying SOPs. All four samples were based on an artificial feed mimicking a formulation for ruminant feed. Two samples were labelled as fish feed (B and D), which was effectuated by adding 2% of a general fish meal. Adulteration was achieved by adding 0.1% pig MBM (B), 0.1% ruminant MBM (D) and a combination of 0.1% ruminant MBM and 0.1% fish meal (C). This combination of different spikes allowed the diverse application of the detection methods. Forty eight participants enrolled for the ring test, of which 45 submitted microscopic results. Of these, 20 participants applied the combination of microscopic and PCR analysis. Three participants submitted exclusively PCR results.
    Dutch Blackworms van waterige reststromen naar sushi
    Elissen, Hellen - \ 2016
    aquaculture - residual streams - industrial effluents - aquatic worms - fish feeding
    Pitch van het seminar 'Innovaties in de productie van aquatische biomassa op afvalwater' op 15 juni 2016 bij ACRRES
    Bruinvissen hebben grote en vette vissen nodig : Promotieonderzoek Mardik Leopold (Wageningen University)
    Leopold, Mardik - \ 2015
    phocoenidae - phocoena - causes of death - starvation - north sea - fish feeding - cetacea
    Minerals in fish: does the source matter?
    Antony Jesu Prabhu, P. - \ 2015
    Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): C. Mariojouls; S. Kaushik; Johan Schrama. - Wageningen : Wageningen University - ISBN 9789462574809 - 267
    visvoeding - mineralen - voedingsstoffenbehoeften - mineraalmetabolisme - voer - minerale supplementen - groei - lichaamssamenstelling - visteelt - aquacultuur - fish feeding - minerals - nutrient requirements - mineral metabolism - feeds - mineral supplements - growth - body composition - fish culture - aquaculture

    Antony Jesu Prabhu, P. (2015). Minerals in fish: does the source matter? PhD thesis. Wageningen University, The Netherlands.

    Minerals are a group of micro-nutrients essential to fish. Meta-analysis of literature data was performed to identify the appropriate response criterion to determine the mineral requirement of fish. The meta-analysis revealed that, vertebral mineral concentrations or specific enzyme activities provide stringent requirement estimates compared to weight gain. Dietary intake forms the major route of mineral supply to fish; however fish are also capable of acquiring dissolved minerals from the rearing water. Changes in the dietary composition or mineral concentration of rearing water could have an impact on the mineral balance in fish. In this thesis, high fat diets, diets devoid, or low in fish meal and rearing systems with high water mineral concentrations were studied for their impact on the mineral balance in rainbow trout or common carp. Increased available phosphorus levels were needed (0.4% vs. 0.8%) in high fat diets to improve whole body and vertebral mineralisation as indicated by ash, P and Ca concentrations. However, supplementing phosphorus to complete plant ingredient based diets negatively affected the absorption and utilisation of micro-minerals namely Zn, Cu and Se. In rainbow trout that received complete plant ingredient based diets, the endogenous loss of Zn was higher and of Cu was lower resulting in Zn depletion and Cu accumulation in the body. Further, the hepatic metabolism of Fe and Cu was affected in rainbow trout fed the plant ingredient based diets, possibly due to the alterations in bile or cholesterol metabolism. With regard to the minimal dietary levels required, supplementation of Zn and Se were required beyond the levels recommended by NRC (2011) to maintain body balance in rainbow trout and common carp when fed complete plant ingredient based diets. Common carp reared in recirculation aquaculture systems (RAS) with high concentration of minerals in the water was able to acquire and retain minerals from water. However, only in the case of Se, they were able to compensate for a part of the dietary requirement. On the whole, higher dietary levels of P and Ca are required in the diet of fast growing rainbow trout; dietary levels of Zn and Se have to be increased beyond present recommended levels in plant ingredient based diets for rainbow trout and common carp. Low water exchange RAS has multiple effects on the whole animal physiology of fish and requires further research for better understanding.

    Microalgae for aquaculture
    Michels, M.H.A. - \ 2015
    Wageningen University. Promotor(en): Rene Wijffels, co-promotor(en): Marian Vermue. - Wageningen : Wageningen University - ISBN 9789462572249
    aquacultuur - aquacultuursystemen - algenteelt - visvoeding - fotobioreactoren - biomassa productie - biobased economy - aquaculture - aquaculture systems - algae culture - fish feeding - photobioreactors - biomass production - biobased economy
    In 2007, the project ‘Zeeuwse Tong’ (Zeeland Sole) was founded with support of the province of Zeeland, the Netherlands. The aim of the Zeeuwse Tong project was to establish an innovative land-based integrated multi-trophic aquaculture sector, which is producing sole, ragworms, algae, shellfish and saline crops in close harmony with nature. The project was divided into two sub-projects: The integrated saline aquaculture farm and the integrated nursery. The research described in this thesis resides within the integrated nursery subproject. In this project the rearing of fingerlings of sole would be combined with the cultivation of microalgae as feed for shellfish larvae and spat inside a greenhouse. An integrated nursery in a greenhouse has several advantages: a greenhouse with a multipurpose use of space, sole culture combined with the cultivation of microalgae and shellfish larvae or spat, an integrated thermoregulation and the reuse of nutrients from the wastewater of the fish basins for the production of microalgae in closed photobioreactors (PBRs). For this thesis, a horizontal tubular PBR needed to be designed and constructed to investigate the productivity and yield of microalgae applied as feed for shellfish larvae or spat, within the context of an integrated nursery.
    De productie van Artemia-cysten, hoeksteen lokale economie in ontwikkelingslanden : ontwikkelingsmodel Tual ( Kleine Keï-eiland, Ind.)
    Scheerboom, J. ; Leenstra, S.H. ; Rothuis, A.J. - \ 2014
    Aquacultuur 29 (2014)3. - ISSN 1382-2764 - p. 11 - 19.
    aquacultuur - visvoeding - artemia - cysten (ontwikkelingsstadia) - prijsbepalende factoren - ontwikkelingslanden - aquaculture - fish feeding - artemia - cysts (developmental stages) - price determining factors - developing countries
    De wereldwijde groei van de aquacultuur had een toename tot gevolg van de vraag naar cysten van Artemia (voor het voeden van larven van vissen en garnalen in een hatchery). Mondiaal worden cysten van zoutwaterkreeftje Artemia gewonnen in natuurlijke, zoute wateren. De beschikbaarheid van cysten is echter beperkt; niet alleen stijgt de vraag, de hoeveelheid te oogsten cysten is ook onvoorspelbaar door de wisselende klimatologische omstandigheden. De wetmatigheden van vraag en aanbod veroorzaken daarom fluctuaties in de prijs.
    Fish silage as feed ingredient for fish and livestock
    Rurangwa, E. ; Vuuren, A.M. van; Poelman, M. - \ 2014
    Yerseke : IMARES (Report / IMARES Wageningen UR C135/14) - 57
    vissilage - voersamenstelling - veevoeding - visvoeding - eiwitbronnen - oost-afrika - visverwerking - vercommercialisering - fish silage - feed formulation - livestock feeding - fish feeding - protein sources - east africa - fish processing - commercialization
    The present report analyses through a literature review the potential of fish silage to valorise fish processing by-products into economically relevant protein sources for fish and livestock feed production in East Africa.
    Feed intake and oxygen consumption in fish
    Subramanian, S. - \ 2013
    Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Johan Schrama; S.J. Kaushik; I. Geurden. - Wageningen : Wageningen UR - ISBN 9789461737571 - 163
    vissen - voeropname - zuurstofconsumptie - energieopname - voer - samenstelling - energiemetabolisme - macronutriënten - visvoeding - visteelt - aquacultuur - voedingsfysiologie - fishes - feed intake - oxygen consumption - energy intake - feeds - composition - energy metabolism - macronutrients - fish feeding - fish culture - aquaculture - nutrition physiology

    In fish, the voluntary feed intake is influenced by dietary, environmental and/or physiological factors. It is well known that under hypoxia the concentration of oxygen in the water (DO) determines the feed intake of fish. However at non-limiting water DO levels (normoxia), several other mechanisms might play a role in feed intake regulation. Under hypoxia feed intake and oxygen consumption are interrelated. In this thesis we proposed the ‘oxystatic’ concept of feed intake regulation, which states that even at normoxia and in the absence of other constraints, the long term (weeks) voluntary feed intake of fish can be constrained by a set-point value of oxygen consumption. Dietary macronutrient composition affects the ‘dietary oxygen demand’ (i.e., amount of O2 consumed per unit of feed). This oxystatic concept implies that fish fed to satiation with diets differing in ‘dietary oxygen demand’ (mg O2/ g or kJ feed) will have a different digestible energy intake but a similar oxygen consumption. The validity of the oxystatic concept was assessed in two species, Nile tilapia and rainbow trout. These fish were fed diets which had large contrasts in nutrient composition (i.e., protein to energy ratio; type of the non-protein energy source (starch vs. fat); amino acid composition) in order to create contrasts in dietary oxygen demand. In all conducted studies with both species, the digestible energy intake was affected by the diet composition. However, in some studies oxygen consumption was similar and in others it differed between the diets, which respectively supports and contradicts the oxystatic concept. In all studies with both species, the digestible energy intake of tilapia and trout was negatively related to dietary oxygen demand and positively related to efficiency of oxygen utilization for energy retention. Furthermore it was observed in tilapia that the within-day variation in feed intake was affected by dietary macronutrient composition. The variation in within-day feed intake was related to pre-feeding oxygen levels. Based on the combined results, it is suggested that even at normoxia voluntary feed intake in fish is limited/determined by oxygen consumption and/or the oxidative metabolism. Overall, the oxystatic concept appears to be valid for certain conditions, but its generic application remains questionable. Yet, the oxystatic concept enables the combination of dietary, environmental and fish factors into one concept. Further it provides a conceptual insight for better understanding of feed intake regulation in fish.

    Towards sustainable fish feed production using novel protein sources
    Draganovic, V. - \ 2013
    Wageningen University. Promotor(en): Remko Boom, co-promotor(en): Atze Jan van der Goot. - S.l. : s.n. - ISBN 9789461736802 - 174
    visvoeding - planteiwitten - tarwe-eiwit - sojaeiwit - koolzaad - lupinemeel - geëxtrudeerde voedingsmiddelen - uitpersing - duurzaamheid (sustainability) - fish feeding - plant proteins - wheat protein - soya protein - rape - lupin meal - extruded foods - extrusion - sustainability

    The consumption of fish and fish-related products is increasing. Due to improved welfare and suggested health benefits, consumers are now eating more fish. In 2008, global fisheries supplied the world with about 142 million tons of fish, of which 115 million tons was used as human food, which is an all-time high (FAO, 2010. The State of World Fisheries and Aquaculture. FAO, Rome, Italy). Fish for consumption can be harvested directly from the wild (capture fisheries), but a growing proportion of the fish comes from worldwide aquaculture (FAO, 2010). As a result, there is an increased need for feed for this growing industry.

    Fish need feed with high levels of protein and energy. Traditionally, for carnivorous or omnivorous fish, these are provided mainly as fish meal and fish oil which are however finite resources and alternative ingredients are needed.

    Any change in composition is not trivial because fish feed pellets need to fulfil strict technological requirements. When feeding to salmon, the pellet should sink slowly. In addition, the porosity of the pellet directly after extrusion should be such that it can capture sufficient oil. The pellets should not break or produce dust during transport and further handling. This makes the production of feed pellets a delicate process in which the techno-functional properties of the raw materials play an important role.

    It is not a simple matter to conclude that plant proteins are more sustainable per se if all the renewable and nonrenewable resources and waste emissions related to the production of these ingredients are taken into account. For example, the use of plant-based ingredients might require additional water during extrusion leading to increased drying costs.

    This thesis describes the relationships between the techno-functional properties of protein-rich ingredients and processing. Criteria have been developed for the use of plant-based materials in existing fish feed processes to allow the production of feed pellets that meet all the product requirements. Feed sustainability is assessed using three different methodologies and sustainable feed compositions are proposed.

    Future trends in the development of sustainable feeds are described based on the insights obtained from this thesis. These include the use of plant proteins that contribute to a more intensified process with the ultimate goal of no drying and future exploration of the use of algae-derived products with special focus on the replacement of fish oil with algae oil.

    Effects of oxygen concentration on the growth of Nannochloropsis sp.
    Raso, S. - \ 2013
    Wageningen University. Promotor(en): Rene Wijffels, co-promotor(en): Marian Vermue. - S.l. : s.n. - ISBN 9789461737472 - 157
    algen - voer - aquacultuur - visvoeding - fotobioreactoren - eicosapentaeenzuur - zuurstof - algae - feeds - aquaculture - fish feeding - photobioreactors - eicosapentaenoic acid - oxygen

    ANannochloropsissp. is a promising microalgal resource for production of food, feed and bio-based commodities, as it can grow relatively fast and combines high lipid content with high content of poly-unsaturated fatty acids. High productivity with constant product quality can be achieved in fully controlled closed photobioreactors. In these closed photobioreactors, however, oxygen accumulation occurs and causes inhibition of the growth by photorespiration combined with photoinhibition.

    The inhibitory effects of photorespiration and photoinhibition can be partly dealt with via the carbon concentration mechanism of the cells and by activation of the water-water cycle. At constant high oxygen concentration and high light intensity, however, the growth of the cells ceases. To our surprise, the accumulating oxygen did not affect the growth rate of the algae if the oxygen was removed regularly. In large scale production in closed photobioreactors, it is thus crucial apply degassing to achieve high algal productivity.

    Protein and energy nutrition of marine gadoids, Atlantic cod (Gadus morhua L.) and haddock (Melanogrammus aeglefinus L.)
    Tibbetts, S. - \ 2012
    Wageningen University. Promotor(en): S.P. Lall; Johan Verreth, co-promotor(en): Johan Schrama. - [S.l.] : s.n. - ISBN 9789461731357 - 221
    kabeljauw - schelvis - zeevissen - voedingseiwit - energie - visvoeding - diervoeding - verteerbaarheid - ingrediënten - mengvoer - voedingsstoffenbehoeften - visteelt - aquacultuur - cod - haddock - marine fishes - dietary protein - energy - fish feeding - animal nutrition - digestibility - ingredients - compound feeds - nutrient requirements - fish culture - aquaculture

    Primary goals of this thesis were to: 1) examine the in vivo digestion of macronutrients from conventional or alternative feed ingredients used in practical diets of juvenile gadoids (Atlantic cod and haddock), 2) document growth potential of fish at the juvenile grower phase given varying levels of dietary protein and energy and 3) assess the potential of in vitro pH-Stat methods for rapid screening protein quality of feed ingredients, specifically for gadoids. All primary research questions were linked to and built upon one another with the goal of gaining a better understanding of protein and energy utilization of juvenile grower phase gadoids. Studies showed that cod and haddock have a high capacity to utilize a wide range of dietary feed ingredients, such as fish meals, zooplankton meal, soybean products (meal, concentrate and isolate) and wheat gluten meal. New dietary formulations for gadoids may also utilize pulse meals, corn gluten meal, canola protein concentrate and crab meal. Digestibility data in this thesis is currently the only research that examined both in vivo and in vitro macronutrient digestibility of a large number and wide range of individual ingredients, specifically for gadoids. This is essential to gain new knowledge on protein and energy utilization as well as for least-cost ration formulations and effective substitution of ingredients into new formulations. Data has demonstrated a dietary digestible protein/digestible energy (DP/DE)ratio of 30 g DP/MJ DE is required for gadoids during the juvenile phase (<100 g) to ensure maximum somatic tissue growth, high digestibility, maximum nitrogen and energy retention efficiency and minimal excessive liver growth. Preliminary nutrient requirement studies together with an applied nutritional approach has identified that feeds for juveniles farmed in the Western North Atlantic should contain 50-55% crude protein, <12% fat and <17% carbohydrate. Data in this thesis is currently the first aimed at development and application of an in vitro closed-system pH-Stat assay for rapid screening protein quality of test ingredients that is ‘species-specific’ to gadoids. It is demonstrated that in vitro results generally reflected results obtained through conventional in vivo protein digestibility methods. Studies resulted in the first generation of a ‘gadoid-specific’ proteolytic enzyme extraction method and in vitro closed-system pH-Stat assay which may be useful to investigate protein digestion, absorption and metabolism of gadoids and further development of their feeds.

    Identification of specific demands on Feed in Dutch Organic Aquaculture
    Poelman, M. - \ 2009
    Yerseke : IMARES (Rapport / Wageningen IMARES C070/09) - 19
    biologische landbouw - aquacultuur - visvoeding - biologische productie - certificering - garnalenteelt - visteelt - vitaminen - dierenwelzijn - organic farming - aquaculture - fish feeding - biological production - certification - shrimp culture - fish culture - vitamins - animal welfare
    The evaluation of specific demands for organic feed focussed on feed demands for four fish species which can be cultured in Recirculation Aquaculture Systems (RAS), tilapia, African Catfish, shrimp and turbot. The evaluation of the various feed formulations indicates that there are several ingredients, which are common for the four species, and will therefore be used for further elaboration on the organic availability. These feed ingredients, are: fishmeal and oil, corn meal, wheat meal, blood meal, vitamin mix, mineral mix, and antioxidants. Besides the evaluation of the feed ingredients an inventory was made on the demands set by three key organic standards and legislation documents; European legislation (in prep), IFOAM and Naturland. A draft consensus standard containing a synthesis of all demands has been described. The implication of the demands, and the possibilities and bottlenecks for organic feed production were evaluated for the selected feed ingredients. It was concluded that organic feed production for RAS can meet the general criteria set for feed, on GMO material and organic composition. However, for the production of organic feed, a bottleneck will be the necessary requirement of synthetic amino acids for health improvement. The lack of these amino acids in organic feed can result in potential disadvantage for animal needs. This raw material restrictions will most likely also result in the lack of possibilities for fine tuning the feed for animal needs
    Etiology of soybean-induced enteritis in fish
    Urán Carmona, P.A. - \ 2008
    Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Johan Schrama; Jan Rombout. - [S.l.] : S.n. - ISBN 9789085049098 - 175
    Europese zalm - karper - sojabonen - visvoeding - enteritis - etiologie - dierpathologie - visteelt - aquacultuur - Atlantic salmon - carp - soyabeans - fish feeding - enteritis - aetiology - animal pathology - fish culture - aquaculture
    The inclusion of soybean meal (SBM), especially in the diet of Atlantic salmon, induces an inflammatory response of the distal intestinal mucosa, known as SBM-induced enteritis. A semi-quantitative scoring system was developed to assess the extent of the morphological changes observed in this study. The influence of SBM feeding has been investigated taking into account several dietary and non-dietary factors possibly involved in the induction of the disorder. It has been found that the severity of enteritis and its kinetics are dose-dependent. Electron microscopy studies indicated a block of the endocytosis process and a strong decrease of the microvilli length. Comparative studies were carried out in an omnivorous species and for the first time ever reported, the results suggested that the symptoms of enteritis also occur in common carp. Contrary to the observations in studies with Atlantic salmon, the common carp started to recover from week four onwards. Several cytokines were presumed to influence this process and they were correlated to the modulation of the inflammatory process triggered by the SBM-containing diet. The influence of different factors was measured according to the degree of enteritis developed. Low temperature (8 °C vs. 12 °C) seems to delay the onset of the symptoms. On the other hand, it was suggested that SBM-induced enteritis was not strongly influenced by either salinity or age. The extent of enteritis in Atlantic salmon depends on the origin and/or the processing of the soybeans. The morphological changes observed were induced when soyasaponins were fed to Atlantic salmon alone or in combination with other soybean components suggesting their possible role on the induction of enteritis. The actual causative components and its mechanisms of action need further research. It is concluded that the etiology and further development of SBM-induced enteritis is related to dietary factors rather than non-dietary factors. SBM inclusion levels and the commercial source used for the diet formulation have a great impact on the severity of the disorder, mainly affecting the endocytosis process. This thesis evidenced that the endocytosis block is directly related to the disappearance of the supranuclear vacuoles, which can be considered as the most striking feature in the onset of enteritis.
    Report Task 2.3: Particulate waste and turbidity in (marine) RAS
    Kals, J. ; Schram, E. ; Brummelhuis, E.B.M. ; Bakel, B. van - \ 2006
    IJmuiden : IMARES (Report / IMARES C070/06) - 41
    afvalbeheer - aquacultuur - feces - visvoeding - biofilms - vaste stoffen - zwevende deeltjes - aquacultuur en milieu - waste management - aquaculture - faeces - fish feeding - biofilms - solids - suspended solids - aquaculture and environment
    Particulate waste management and removal is one of the most problematic parts of recirculation aquaculture systems (RAS). Particulate waste and thereby turbidity originates from three major sources: fish (faeces), feed and biofilm (heterotrophic bacteria and fungi). Based on size and density there are roughly four categories of particulate waste: settable, suspended, floatable and fine or dissolved solids. Specific problems related to high turbidity are a decreasing feed intake by fish, causing lower growth and increasing feed loss; an increasing risk regarding pathogens increasing disease problems and gill irritation; a higher oxygen consumption of the system and more complicate visual observation of fish, which is a necessity for good farm management. Good particulate matter and turbidity control is one of the key factors determining the success of RAS. The goal of this task is to get a better understanding of the nature of turbidity and the role of the different water treatment units within RAS and finally find ways to achieve a better control of turbidity.
    Dietary carbohydrate and faecal waste in the Nile Tilapia (Oreochromis niloticus L.)
    Amirkolaie, A.K. - \ 2005
    Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Johan Schrama. - Wageningen : - ISBN 9789085042990 - 143
    Tilapia - Oreochromis niloticus - visvoeding - voedingskoolhydraten - feces - consistentie - uitwerpselen verzamelen - vismest - waterkwaliteit - visteelt - verontreiniging - Tilapia - Oreochromis niloticus - fish feeding - dietary carbohydrate - faeces - consistency - faeces collection - fish manure - water quality - fish culture - pollution
    Public concerns about environmental pollution are putting increasing pressure on fish farms to treat their wastewater before release. The wastewater produced by the fish can also deteriorate water quality within the system. Aquaculture waste can be divided into solid waste and dissolved waste.Faeces ismain sources of solid waste. An increased consistency of faeces may improve its removal efficiency, thereby improving water quality. The removal efficiency of faeces by a collector (settling tank and/or Choubert) was proposed as an indicator for faeces consistency. Manipulation of the diet composition changed faeces consistency in tilapia. Soluble non-starch polysaccharide increased digesta viscosity and reduced faeces removal efficiency. Insoluble non-starch polysaccharide did not change faeces removal. Replacement of native starch by gelatinized starch improved faeces removal efficiency. Fermentation and viscosity of digesta are the main parameters affecting faeces consistency. An increased faeces removal, induced by dietary composition, lowered the organic matter load into the system, thereby increasing nitrification and dissolved oxygen. A detailed investigation on fermentability and viscosity of different ingredients can provide insight in characterization of faeces, thereby giving suggestion for diet formulation geared to maximize solid removal.
    Lactobacillus plantarum 44a as a live feed supplement for freshwater fish
    Bucio Galindo, A. - \ 2004
    Wageningen University. Promotor(en): Frans Rombouts; Johan Verreth, co-promotor(en): Ralf Hartemink. - Wageningen : - ISBN 9789058089434 - 132
    lactobacillus plantarum - zoetwatervissen - probiotica - voedersupplementen - visvoeding - lactobacillus plantarum - freshwater fishes - probiotics - feed supplements - fish feeding
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