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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Feeds, water quality, gut morphology and digestion in Nile tilapia (Oreochromis niloticus)
Trần Ngọc Thiên Kim, Kim - \ 2017
University. Promotor(en): Johan Verreth, co-promotor(en): Johan Schrama; Arjen Roem. - Wageningen : Wageningen University - ISBN 9789463431484 - 127
tilapia - oreochromis niloticus - feeds - fish feeding - water quality - digestion - digestibility - intestines - morphology - fish culture - aquaculture - 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.

Salinity and diet composition affect digestibility and intestinal morphology in Nile tilapia (Oreochromis niloticus)
Tran, Kim ; Schrama, Johan W. ; Le, Mai T.T. ; Nguyen, Thinh H. ; Roem, Arjen J. ; Verreth, Johan A.J. - \ 2017
Aquaculture 469 (2017). - ISSN 0044-8486 - p. 36 - 43.

An increase in salinity of the aquatic habitat can be an environmental stress factor for fresh aquatic organism, including fish. The present study investigated the impact of salinity and diet composition on digestibility and intestinal morphology of Nile tilapia. Triplicate groups of 35 fish weighing 35 g were fed a “Control” and “Test” diet and kept at salinity of 0‰ and 15‰ for 8 weeks. The diets were formulated using a different soybean meal content to create a contrast in alterations in intestinal morphology. Six fish per treatment were sampled for intestinal morphology analysis at the end of weeks 1, 4 and 8. The proximal, middle and distal intestine were processed for quantitative histology, in order to count the number of goblet cells and eosinophilic granulocytes; and to measure the thickness of lamina propria and sub-epithelia mucosa. The study showed that a salinity of 15‰ increased the nutrient digestibility; however this enhanced digestibility diminished over time. The intestinal morphology was influenced by both the salinity as well as the dietary soybean meal content. For soybean meal, the impact on morphology was largest in the proximal region of the intestine, whereas for salinity the largest impact was in the distal region. The negative effect of increased soybean meal on the lamina propria thickness was enhanced at a salinity of 15‰ and aggravated in time. Difference in nutrient digestibility induced by the salinity seemed not to be related to alterations in the intestinal morphology.

Aquaculture Europe 2016
Roem, Arjen - \ 2016
Nile tilapia - organic acids - intestinal morphology - Oreochromis niloticus
Interaction between dissolved oxygen concentration and diet composition on growth, digestibility and intestinal health of Nile tilapia (Oreochromis niloticus)
Tran, N.T.K. ; Dinh, Ngu T. ; Tin, Nguyen Hong ; Roem, A.J. ; Schrama, J.W. ; Verreth, J.A.J. - \ 2016
Aquaculture 462 (2016). - ISSN 0044-8486 - p. 101 - 108.
Nile Tilapia - Oxygen level - Soybean meal - Intestial morphology - intestial health - Digestibility
The present study was undertaken to evaluate the individual and combined effects of oxygen concentration and diet composition on the growth, nutrient utilization and intestinal morphology of Nile tilapia (Oreochromis niloticus). Two recirculating aquaculture systems were used to create the difference in oxygen concentration: normoxia (6.9 mg·L− 1) and hypoxia (3.5 mg·L− 1). Two diets were formulated using a different soybean meal (SBM) content to create a contrast in the potential to affect the gut barrier function. Triplicate groups of 35 fish with initial mean body weight of 23 g were fed “Control” diet containing 20% fish meal and “Test” diet containing only plant protein source at normoxia and hypoxia for 8 weeks. Six fish per treatment were sampled for intestinal morphological analysis at the end of week 1, 4 and 8. The proximal, middle and distal intestine were processed for quantitative histology, in order to count goblet cells (GC) and eosinophilic granulocytes (EG); and to measure the thickness of lamina propria (LP) and sub-epithelial mucosa (SM). The study showed that growth was best in the “Control” diet under normoxia, while no interaction between oxygen and diet composition was found. Hypoxia reduced nutrient digestibility significantly (p < 0.05). For the “Test” diet, the decline in digestibility was larger than for “Control” diet over time. Both diet composition and oxygen level induced changes in intestinal morphology of Nile tilapia. We observed a thickening of the LP and SM caused by an increased infiltration of inflammatory cells, and an increased number of GC and EG among the enterocytes. The negative effect of increased soybean meal on intestinal morphology was enhanced at low oxygen level and aggravated in time. The SBM enteritis-like symptoms were more pronounced in the proximal than in the distal intestine of Nile tilapia.
Effects of immunostimulants on survival of nile tilapia (oreochromis niloticus) after streptococcus agalactiae challenge
Tran, N.T.K. ; Roem, A.J. ; Tin, Nguyen Hong ; Verreth, J.A.J. - \ 2016
Bacterial translocation and in vivo assessment of intestinal barrier permeability in Rainbow trout (Oncorhynchus mykiss) with and without soyabean meal-induced inflammation
Mosberian Tanha, Peyman ; Overland, M. ; Landsverk, Thor ; Reveco, Felipe E. ; Schrama, J.W. ; Roem, A.J. ; Agger, Jane W. ; Midland, Liv T. - \ 2016
Journal of Nutritional Science 5 (2016). - ISSN 2048-6790 - 10 p.
rainbow trout - soyabean meal - enteritis - Intestinal permeability - permeability markers
The primary aim of this experiment was to evaluate the intestinal barrier permeability in vivo in rainbow trout (Oncorhynchus mykiss) fed increasing levels of soyabean meal (SBM). The relationship between SBM-induced enteritis (SBMIE) and the permeability markers was also investigated. Our results showed that the mean score of morphological parameters was significantly higher as a result of 37·5 % SBM inclusion in the diet, while the scores of fish fed 25 % SBM or lower were not different from those of the fish meal-fed controls (P < 0·05). SBMIE was found in the distal intestine (DI) in 18 % of the fish (eleven of sixty): ten in the 37·5 % SBM-fed group and one in the 25 % SBM-fed group. Sugar markers in plasma showed large variation among individuals probably due to variation in feed intake. We found, however, a significant linear increase in the level of plasma d-lactate with increasing SBM inclusion level (P < 0·0001). Plasma concentration of endotoxin was not significantly different in groups with or without SBMIE. Some individual fish showed high values of endotoxin in blood, but the same individuals did not show any bacterial translocation. Plasma bacterial DNA was detected in 28 % of the fish with SBMIE, and 8 % of non-SBMIE fish (P = 0·07). Plasma concentration of d-lactate was significantly higher in fish with SBMIE (P < 0·0001). To conclude, SBMIE in the DI of rainbow trout was associated with an increase in bacterial translocation and plasma d-lactate concentration, suggesting that these permeability markers can be used to evaluate intestinal permeability in vivo.
Aquaculture Europe 2015 EAS International Conference & Exposition
Roem, Arjen - \ 2015
Nile tilapia - Oreochromis niloticus
Effect of oxygen level and dietary composition on growth performance and intestinal morphology in Nile Tilapia (Oreochromis niloticus)
Tran, N.T.K. ; Dinh, N. ; Nguyen, T. ; Roem, A.J. ; Schrama, J.W. ; Verreth, J.A.J. - \ 2015
Sapwood allocation in tropical trees: a test of hypotheses
Schippers, P. ; Vlam, M. ; Zuidema, P.A. ; Sterck, F.J. - \ 2015
Functional Plant Biology 42 (2015)7. - ISSN 1445-4408 - p. 697 - 709.
temperate forest trees - global vegetation models - carbon allocation - shade-tolerance - rain-forest - biomass allocation - seasonal dynamics - use efficiency - climate-change - growth habits
Carbon allocation to sapwood in tropical canopy trees is a key process determining forest carbon sequestration, and is at the heart of tree growth and dynamic global vegetation models (DGVM). Several allocation hypotheses exist including those applying assumptions on fixed allocation, pipe model, and hierarchical allocation between plant organs. We use a tree growth model (IBTREE) to evaluate these hypotheses by comparing simulated sapwood growth with 30 year tree ring records of the tropical long-lived tree Toona ciliata M. Roem. in Thailand. Simulated annual variation in wood production varied among hypotheses. Observed and simulated growth patterns matched most closely (r2 = 0.70) when hierarchical allocation was implemented, with low priority for sapwood. This allocation method showed realistic results with respect to reserve dynamics, partitioning and productivity and was the only one able to capture the large annual variation in tree ring width. Consequently, this method might also explain the large temporal variation in diameter growth and the occurrence of missing rings often encountered in other tropical tree species. Overall, our results show that sapwood growth is highly sensitive to allocation principles, and that allocation assumptions may greatly influence estimated carbon sequestration of tropical forests under climatic change.
Effect of immunostimulants on survival of Nile Tilapia (Oreochromis niloticus) after Streptococcus agalactiae challenge
Tran, N.T.K. ; Roem, A.J. ; Nguyen, T.H. ; Verreth, J.A.J. - \ 2014
Immunostimulants For Growth, Intestinal Healh, Immune Response Andstreptococcus Agalactiae Challenge Survival Of Tilapa (Oreochromis Niloticus)
Tran, N.T.K. ; Roem, A.J. ; Nguyen, T.H. ; Verreth, J.A.J. ; Schrama, J.W. - \ 2014
Aquaculture in East Africa : a regional approach
Rothuis, A.J. ; Turenhout, M.N.J. ; Duijn, A. van; Roem, A.J. ; Rurangwa, E. ; Katunzi, E.F.B. ; Shoko, A. ; Kabagambe, J.B. - \ 2014
IJmuiden / Den Haag : IMARES / LEI (Report / IMARES Wageningen UR C153/14) - 54
aquacultuur - oost-afrika - aquaculture - east africa
Asian-Pacific Aquaculture 2013
Roem, Arjen - \ 2013
Joris Luyendijk als biechtvader
Jongeneel, R. - \ 2013
Sophie 3 (2013)6. - ISSN 2211-4408 - p. 44 - 45.
Joris Luyendijk verwierf roem met zijn boek Het zijn net mensen. Daarin laat hij op grond van zijn ervaring als correspondent in het Midden-Oosten zien hoe de media ons beeld van de wereld vervormen. Tegenwoordig houdt hij voor The Guardian een blog bij over de financiële wereld.
Effect of plant feedstuffs on nutritional physiology and intestinal health of Tilapia Oreochromis niloticus
Tran, N.T.K. ; Roem, A.J. ; Schrama, J.W. ; Jaklofsky, M.T.J. ; Verreth, J.A.J. - \ 2013
Plant feedstuffs have been widely used as an alternative for fish meal due to reasonable price and acceptable protein concentration. However, plant feedstuffs are known to contain anti-nutritional factors that may affect fish performance, Some of these factors have also been implicated in intestinal disorders in several species such as Atlantic salmon, carp or trout. It is generally assumed that tilapia is tolerant to the use of plant feedstuffs, but effects on the intestinal level have not been documented. There is a general lack of knowledge on how to define intestinal ‘health’ in fish and how it is affected by sudden changes in diet composition. Histology was used to assess intestinal health, focussing on gut barrier function. In the current study, we assessed temporal effects of a sudden change in diet composition on the nutrient digestibility capacity and intestinal health of tilapia during a 6-week period. Tilapia fingerlings were reared on a fish meal based diet until they reached about 10 grams at the start of the experiment. Then, they were suddenly switched to one of seven experimental diets: 1) a basal diet based in fishmeal as protein source, 2) using feather meal, 3) using different plant proteins: soybean, canola, sunflower, rice bran and distillers dried grain with solubles (DDGS). The experimental diets 2-7 were based on basal diet 1 whereby part of the diet is replaced by one of the plant proteins or animal protein (70% basal diet plus 30% test ingredient). All diets contained yttriumoxide as a marker. All diets were tested in triplicate tanks, each with 35 fish per tank. Feeds were fed restricted twice daily to 3% body weight. Fish and feaces were sampled after 1, 3 and 6 weeks to study short term and longer term adaption to the diets. Faeces was collected by separate settling tanks. Overall growth and feed efficiency was calculated at the end-of-experiment. Water was recirculated over a large biofilter; oxygen, ammonia, nitrite and nitrate were regularly monitored and water temperature was kept at 280C. Fish (2 per tank per period) were sampled for stomach pH, histology of stomach and proximal, mid and distal parts of the intestine. A new method for quantitative scoring of the histology slides was developed. At the moment of submitting the abstract, the 6-week experiment with tilapia was finished, but most analyses including histological evaluation remained to be done. We will present and discuss our findings at the conference.
Aquaculture business opportunities in Egypt
Rothuis, A.J. ; Duijn, A.P. van; Roem, A.J. ; Ouwehand, A. ; Pijl, W. van der; Rurangwa, E. - \ 2013
Wageningen : Wageningen UR (LEI report 2013-039) - 34
aquacultuur - voedselproductie - voedselzekerheid - plattelandsontwikkeling - bedrijfseconomie - handelsrelaties - egypte - overheidsbeleid - nederland - aquaculture - food production - food security - rural development - business economics - trade relations - egypt - government policy - netherlands
Egyptian fish farming has witnessed a spectacular development resulting in an industry that is number 7 worldwide and number 2 in tilapia production. As such the industry is an important contributor to Egypt's economy as well as a major provider of cheap fish protein. However there are a number of developments that potentially could result in a stagnation or even collapse of the industry.
Techniques in feed formulation and measure nutrient requirement for aquatic animals
Roem, Arjen - \ 2012
Reservering van Zeeuwse glorie voor vogels?
Gosselink, A.M.M. ; Verdegem, M.C.J. ; Reijbroek, A. - \ 2008
Aquacultuur 23 (2008)3. - ISSN 1382-2764 - p. 31 - 35.
mosselteelt - mossels - schaal- en schelpdierenvisserij - mariene ecologie - zeeland - boomkorvisserij - visserij-ecologie - mussel culture - mussels - shellfish fisheries - marine ecology - beam trawling - fisheries ecology
Het zwarte goud, de Zeeuwse roem. Wie kent ze niet? De smakelijke tweekleppige weekdieren die in het najaar weer volop te verkrijgen zijn in restaurants. Mosselen zijn dan ook niet zomaar voedsel, maar ze zijn een onderdeel van de Zeeuwse cultuur. Yerseke is de plaats waar de meeste mosselen van Europa worden verhandeld. Het dorpje bruist door de rijke mossel- en oestercultuur. De Zeeuwse afkomst van mosselen is onlangs zelfs een onderwerp van een rechtzaak geweest. Zeeuwse producten van mosselen vinden dat een mossel pas `Zeeuws¿ genoemd mag worden als de mossel in kwestie ook daadwerkelijk in Zeeuws water heeft geleefd. Productenen van importmosselen mogen dus niet zomaar met de Zeeuwse identiteit aan de haal gaan. Helaas zijn er ook andere, ecologische problemen rond de productie van dit weekdier aan de orde. Over die problemen gaat dit artikel
Monitoring mosselzaadinvang Voordelta in 2007
Gool, A.C.M. van; Poelman, M. - \ 2008
Yerseke : IMARES (Rapport / IMARES Wageningen UR C003/08) - 24
mosselteelt - mossels - schaal- en schelpdierenvisserij - visserijbeheer - onderzoek - visserij-ecologie - voordelta - mussel culture - mussels - shellfish fisheries - fishery management - research - fisheries ecology
Roem van Yerseke test een voor Nederland nieuwe manier van mosselzaadinvang (MZI) op vier locaties in de Voordelta.De volgende gegevens zijn bepaald: het moment van zaadval, de groeisnelheid van het zaad, de dichtheid van het zaad. De oogst wordt gepresenteerd op basis van de door Roem van Yerseke opgegeven oogstgegevens. Er werd een relatief hoog aantal mosselzaad aangetroffen met een hoge gemiddelde lengte. Het is uit de experimenten gebleken dat het monitoringtouw, dat additioneel aan het systeem is gehangen, zich mogelijk afwijkend gedraagt van het MZI/systeem, waardoor vergelijking op oogstniveau moeilijk is. Voor vervolgstudies wordt geadviseerd monstergegevens te verkrijgen van het invangsysteem zelf.
Outdoor mass production of marine diatoms with ground water from Roem van Yerseke, The Netherlands. Essays on its feasibility
Batista, I. - \ 2006
Yerseke : IMARES (Report / IMARES 06.016) - 53 p.
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