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.

    We have a manual that explains all the features 

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    Boeren uit onze provincie voeden miljoenen monden Veel meer dan we in Utrecht op kunnen
    Berkhout, Petra - \ 2019
    Hoogleraar: 'Aantal zaken waar je op moet letten als je duurzame vis koopt'
    Wiegertjes, G. - \ 2019

    Van jongs af aan leren we dat vis goed is voor de gezondheid. Maar hoe verantwoord is het nou om vis te eten?

    "Verantwoord vis eten is zeker mogelijk", zegt Geert Wiegertjes, hoogleraar Aquacultuur en Visserij aan de Wageningen Universiteit. "Er zijn wel een aantal zaken waarop je moet letten als je duurzame vis wil kopen."

    "Let allereerst op de keurmerken op de verpakking", licht Wiegertjes toe. Hij doelt hiermee op de keurmerken van de Marine Stewardship Council (MSC) en Aquaculture Stewardship Council (ASC).

    MSC is het keurmerk voor visproducten afkomstig uit de duurzame visserij. Het betekent dat visstanden duurzaam worden beheerd, het leven in de zee zo min mogelijk schade wordt toegebracht en er weinig bijvangst is.

    ASC is vergelijkbaar met het MSC-keurmerk, maar dan voor kweekvis. Het keurmerk kent regels voor minder antibioticagebruik, duurzamer visvoer en betere arbeidsomstandigheden van het personeel.

    Tips om verantwoord vis te eten:

    • • Koop vis met het MSC- of ASC-keurmerk.
    • • Ga voor biologisch als je dierenwelzijn belangrijk vindt.
    • • Zoek vis zonder keurmerk (bijvoorbeeld van de visboer) op in de VISwijzer.
    • • Eet ook eens een vis die goed scoort volgens de Bijvangstwijzer.

    "Deze keurmerken houden overigens geen rekening met het dierenwelzijn", benadrukt Wiegertjes. Dit is wel het geval bij het keurmerk 'biologisch'.

    "Biologische vis is altijd gekweekte vis, aangezien de omstandigheden van wilde vis niet kunnen worden gecontroleerd. Bij biologische vis worden meer eisen aan dierenwelzijn gesteld. Bijvoorbeeld aan het aantal vissen per kubieke meter. Ook moeten de vissen bij de slacht bewusteloos en vrij van pijn zijn en is het gebruik van hormonen verboden."

    Drie kwart van de supermarktvis heeft een keurmerk

    Uit onderzoek van MSC en ASC blijkt dat 74 procent van de visproducten in de Nederlandse supermarkt een van deze twee keurmerken heeft. Bij ingeblikte vis is echter nog een hoop te winnen. Minder dan de helft (48 procent) heeft het MSC- of ASC-keurmerk. Dit percentage is de afgelopen jaren wel gestegen.

    Opmerkelijk is verder dat van de diervoeding met vis slechts 28 procent een van de twee keurmerken heeft. Overigens bestaan er ook verschillen tussen producten van hetzelfde merk. Het ene blik kan wel een MSC- of ASC-keurmerk hebben, terwijl een ander blik van hetzelfde merk juist geen keurmerk heeft.

    Verder hebben de meeste visconserven het Dolphine SAFE-logo. In een eerder interview met NU.nl noemen twee deskundigen dit keurmerk misleidend. Het gaat volgens deze experts over een probleem dat niet meer speelt. Jaren geleden was er inderdaad sprake van een problematische bijvangst van dolfijnen. Nu gebeurt dat nauwelijks meer.

    Wie in de supermarkt vis koopt, kan letten op de keurmerken. Die zijn terug te vinden op de verpakking. (Foto: Pixabay)

    Er is ook kritiek op de keurmerken

    Toch is er ook regelmatig kritiek op het MSC- en ASC-keurmerk. Zo zou een aantal visserijen geen MSC-certificaat verdienen en zouden de financiële belangen enorm zijn. De Correspondent concludeerde twee jaar geleden dat het keurmerk inderdaad niet zaligmakend is, maar dat je toch het best wel vis met een van de twee keurmerken kunt kopen.

    Vooral de tonijnvangst had de afgelopen jaren een slechte naam. Uit het project BESTTuna, waar ook de Wageningen Universiteit aan deelnam, blijkt dat een aantal tonijnpopulaties weer grotendeels is hersteld.

    Wiegertjes: "Steeds vaker is de hoeveelheid gevangen tonijn weer acceptabel. En dit geldt zelfs weer voor de bonito, een tonijnsoort die wordt gevangen in de Middellandse Zee. Men is zich tegenwoordig wereldwijd steeds meer bewust van het feit dat we niet méér vis moeten vangen dan goed is voor het ecosysteem."

    Land van herkomst en manier van vangen

    Moet je vis zonder keurmerk daarom per definitie links laten liggen? "Een lastige vraag", zegt Wiegertjes. "Dat ligt ook aan het land van herkomst en de manier waarop de vis gevangen is." De hoogleraar vindt dan ook dat fabrikanten verplicht moeten worden om de herkomst en manier van vangst te vermelden op de verpakking.

    Zie ook: Van eigen bodem: De schar en dit kun je ermee

    De vis bij de visboer is vaak onverpakt en ligt op ijs, waardoor je niet in een oogopslag kunt zien of de vis het MSC- of ASC-keurmerk heeft. Je kunt de visboer hiernaar vragen en ieder geval vragen waar de vis vandaan komt.

    Vervolgens kun je in de VISwijzer van de Good Fish Foundation nagaan hoe duurzaam de vis is.

    Bijvangst uit de Noordzee die goed scoort op het gebied van duurzaamheid:

    • • Schar
    • • Wijting
    • • Grauwe poon
    • • Steenbolk
    • • Bot
    • • Heek
    • • Koolvis
    • • Witje (hondstong)
    • • Harder
    • • Schelvis
    • • Zeekat

    Bijvangst uit Noordzee die niet goed scoort op het gebied van duurzaamheid:

    • • Horsmakreel
    • • Mul
    • • Wulk
    • • Zeeduivel
    • • Zonnevis
    • • Haai
    • • Rog

    Bron: bijvangstwijzer.nl

    Bloemisten verkopen nog altijd het ‘groene monster’, de Japanse duizendknoop
    Dijk, Chris van - \ 2019
    Koop geen sojabonen meer uit ontbost gebied, en nog vijf tips
    Wicke, Birka ; Visseren-Hamakers, Ingrid ; Wassen, Martin ; Verweij, Pita ; Dekker, Stefan ; Hilst, Floortje van der; Turnhout, Esther ; Behagel, Jelle - \ 2019
    NRC Handelsblad
    Duurzaamheid Nederland moet het voortouw nemen bij het uitbreiden van de Europese wetgeving tegen wereldwijde ontbossing, schrijven acht wetenschappers.
    Failure costs associated with mastitis in smallholder dairy farms keeping Holstein Friesian × Zebu crossbreed cows
    Mekonnen, S.A. ; Koop, G. ; Getaneh, A.M. ; Lam, T.J.G.M. ; Hogeveen, H. - \ 2019
    Animal 13 (2019)11. - ISSN 1751-7311 - p. 2650 - 2659.
    clinical mastitis - dairy - failure cost - smallholder farms - subclinical mastitis

    Mastitis is a costly disease and in many areas of the world, these costs have been quantified to support farmers in their decision making with regard to prevention of mastitis. Although for subsaharan circumstances estimates have been made for the costs of subclinical mastitis (SCM), farm-specific cost estimations comprising both clinical mastitis (CM) and SCM are lacking. In this paper, we quantified failure costs of both CM and SCM on 150 Ethiopian market-oriented dairy farms keeping Holstein Friesian × Zebu breed cows. Data about CM were collected by face-to-face interviews and the prevalence of SCM was estimated for each farm using the California mastitis test. All other relevant information needed to calculate the failure costs, such as the consequences of mastitis and price levels, was collected during the farm visits, except for the parameter for milk production losses due to SCM, which was based on literature estimates and subjected to sensitivity analyses. The average total failure costs of mastitis was estimated to be 4 765 Ethiopian Birr (ETB) (1 ETB = 0.0449 USD) per farm per year of which SCM contributed 54% of the costs. The average total failure costs per lactating cow per farm per year were 1 961 ETB, with a large variation between farms (range 0 to 35 084 ETB). This large variation in failure costs between farms was mainly driven by variation in incidence of CM and prevalence of SCM. Milk production losses made the largest contribution (80%), whereas culling contributed 13% to 17% to the total failure costs. In our estimates, costs of veterinary services, drugs, discarded milk and labour made a minor contribution to the total failure costs of mastitis. Relative to the income of dairy farmers in North Western Ethiopia; the total failure costs of mastitis are high. In general, Ethiopian farmers are aware of the negative consequences of CM, but creating awareness of the high costs of SCM and showing large variation between farmers may be instrumental in motivating farmers to also take preventive measures for SCM.

    Farm-level risk factors for bovine mastitis in Dutch automatic milking dairy herds
    Deng, Z. ; Koop, G. ; Lam, T.J.G.M. ; Lans, I.A. van der; Vernooij, J.C.M. ; Hogeveen, H. - \ 2019
    Journal of Dairy Science 102 (2019)5. - ISSN 0022-0302 - p. 4522 - 4535.
    automatic milking system - mastitis - nonlinear principal component analysis - principal component regression - risk factor

    Automatic milking systems (AMS) are installed on a growing number of dairy farms worldwide. Management to support good udder health might be different on farms with an AMS compared with farms milking with a conventional milking system, as risk factors for mastitis on farms using an AMS may differ. The aim of this study was to identify farm level factors associated with mastitis on Dutch dairy farms using an AMS. In 2008, risk factor data were collected using a questionnaire combined with on-farm recordings of cow, stall, and AMS hygiene on 135 farms. These risk factor data were linked to 4 udder-health-associated dependent variables: average herd somatic cell count (HeSCCav), variance of the average herd somatic cell count (SCC) on test days (HeSCCvar), the average proportion of new high SCC cases (NHiSCC), and the farmer-reported annual incidence rate of clinical mastitis (IRCM). We employed regression models using multiple imputation to deal with missing values. Due to the high dimensionality of the risk factor data, we also performed nonlinear principal component analysis (NLPCA) and regressed the dependent variables on the principal components (PC). Good hygiene of cows and of AMS were found to be related to a lower HeSCCav and less NHiSCC. Effective postmilking teat disinfection was associated with a lower NHiSCC. A higher bulk tank milk SCC threshold for farmers' action was related to more NHiSCC. Larger farm size was related to lower HeSCCvar but higher NHiSCC. Negative attitude of farmers to animal health, higher frequency of checking AMS, and more time spent on viewing computer data were all positively related to higher IRCM. An NLPCA with 3 PC explained 16.3% of the variance in the risk factor variables. Only the first 2 PC were associated with mastitis. The first PC reflected older and larger farms with poor cow hygiene and AMS hygiene, and was related to higher HeSCCav and NHiSCC, whereas the second PC reflected newly built smaller farms with poor cow hygiene and low milk production, and was associated with higher HeSCCvar and NHiSCC, but lower IRCM. Our study suggests that many of the risk factors on conventional milking system farms are applicable to AMS farms, specifically concerning hygiene of the cows and the milking machine, but on large AMS farms, udder health may need more attention than on smaller AMS farms. Multiple imputation is instrumental to deal with missing values and NLPCA is a useful technique to process high dimensional data in our study.

    Discovery of Sabellaria spinulosa reefs in an intensively fished area of the Dutch Continental Shelf, North Sea
    Reijden, Karin J. Van Der; Koop, Leo ; O'flynn, Sarah ; Garcia, Silvia ; Bos, Oscar ; Sluis, Christiaan Van; Maaholm, David J. ; Herman, Peter M.J. ; Simons, Dick G. ; Olff, Han ; Ysebaert, Tom ; Snellen, Mirjam ; Govers, Laura L. ; Rijnsdorp, Adriaan D. ; Aguilar, Ricardo - \ 2019
    Journal of Sea Research 144 (2019). - ISSN 1385-1101 - p. 85 - 94.
    Biogenic Reef - Brown Bank - Ecosystem Engineer - Sabellaria spinulosa - North Sea
    The tube-building polychaete Sabellaria spinulosa (Ross worm) can form conspicuous biogenic reefs that stabilize the seabed and increase biodiversity by providing a habitat for a multitude of other species. These reefs, however, are assumed to be vulnerable to human-induced physical disturbances of the seabed. In the Greater North Sea, S. spinulosa reefs are recognized to be under threat and worthy of protection. In August 2017, three S. spinulosa reefs with a minimum extent of 1016m2 were discovered in the Dutch Brown Bank area. This area comprises a large-scale sandbank and adjacent troughs. The reefs were found within the sandbank troughs, which have proven to be subject to high demersal fishing intensities (fished>5 times a year). Detailed bathymetry measurements showed that S. spinulosa reefs were mainly located within valleys of smaller-scaled sand waves, which have a perpendicular orientation compared to the large-scale sandbank structure of the Brown Bank. We hypothesize that the valleys in between sand waves offer suitable substrate for settlement and refuge from abrasion by fishing activities, enabling the S. spinulosa reefs to persist despite high fishing intensities. ROV footage of the reefs showed higher estimates of species abundances on the reefs compared with adjacent habitats, with some species present that are typical for hard substrate (rock gunnel, Pholis gunnellus; edible crab, Cancer pagurus; and velvet swimming crab, Necora puber). The information presented could be used for drafting management policies to protect these reefs, as Contracting Parties of the OSPAR Convention are committed to take measures and protect biodiversity.
    Comparing four diagnostic tests for Giardia duodenalis in dogs using latent class analysis
    Uiterwijk, Mathilde ; Nijsse, Rolf ; Kooyman, Frans N.J. ; Wagenaar, J.A. ; Mughini-Gras, Lapo ; Koop, Gerrit ; Ploeger, Harm W. - \ 2018
    giardiasis - canine - prevalence - diagnosis - Bayesian analysis
    Background To accurately diagnose giardiosis in dogs, knowledge of diagnostic test characteristics and expected prevalence are required. The aim of this work was to estimate test characteristics (sensitivity and specificity) of four commonly used diagnostic tests for detection of Giardia duodenalis in dogs. Methods Fecal samples from 573 dogs originating from four populations (household dogs, shelter dogs, hunting dogs and clinical dogs) were examined with centrifugation sedimentation flotation (CSF) coproscopical analysis, direct immunofluorescence assay (DFA, Merifluor Cryptosporidium/Giardia速), a rapid enzyme immunochromatographic assay (IDEXX SNAP Giardia速) and qPCR (SSU rDNA) for presence of G. duodenalis. Bayesian latent class analysis was used to determine test performance characteristics and to estimate G. duodenalis prevalence of each of the four dog populations. Results All tests were highly specific. IDEXX SNAP Giardia速 showed the highest specificity (99.6%) and qPCR the lowest (85.6%). The sensitivities were much more variable, with qPCR showing the highest (97.0%) and CSF the lowest (48.2%) sensitivity. DFA was more sensitive than IDEXX SNAP Giardia速, but slightly less specific. Prevalences of G. duodenalis differed substantially between populations, with the hunting dogs showing the highest G. duodenalis prevalence (64.9%) and the household dogs the lowest (7.9%). Conclusions This study identifies qPCR as a valuable screening tool because of its high sensitivity, whereas methods using microscopy for cyst identification or cyst wall detection should be used in situations where high specificity is required. G. duodenalis is a prevalent gastro-intestinal parasite in Dutch dogs, especially in dogs living in groups (hunting and shelter dogs) and clinical dogs.
    ‘Als je slim tomaten teelt krijg je energiebesparing op de koop toe’: onderzoekers, adviseurs en telers delen kennis over HNT
    Gelder, A. de - \ 2018
    Comparing four diagnostic tests for Giardia duodenalis in dogs using latent class analysis
    Uiterwijk, Mathilde ; Nijsse, Rolf ; Kooyman, Frans N.J. ; Wagenaar, Jaap A. ; Mughini-Gras, Lapo ; Koop, Gerrit ; Ploeger, Harm W. - \ 2018
    Parasites & Vectors 11 (2018)1. - ISSN 1756-3305
    Bayesian analysis - Canine - Diagnosis - Giardiasis - Prevalence

    Background: To accurately diagnose giardiosis in dogs, knowledge of diagnostic test characteristics and expected prevalence are required. The aim of this work was to estimate test characteristics (sensitivity and specificity) of four commonly used diagnostic tests for detection of Giardia duodenalis in dogs. Methods: Fecal samples from 573 dogs originating from four populations (household dogs, shelter dogs, hunting dogs and clinical dogs) were examined with centrifugation sedimentation flotation (CSF) coproscopical analysis, direct immunofluorescence assay (DFA, Merifluor Cryptosporidium/Giardia®), a rapid enzyme immunochromatographic assay (IDEXX SNAP Giardia®) and qPCR (SSU rDNA) for presence of G. duodenalis. Bayesian latent class analysis was used to determine test performance characteristics and to estimate G. duodenalis prevalence of each of the four dog populations. Results: All tests were highly specific. IDEXX SNAP Giardia® showed the highest specificity (99.6%) and qPCR the lowest (85.6%). The sensitivities were much more variable, with qPCR showing the highest (97.0%) and CSF the lowest (48.2%) sensitivity. DFA was more sensitive than IDEXX SNAP Giardia®, but slightly less specific. Prevalences of G. duodenalis differed substantially between populations, with the hunting dogs showing the highest G. duodenalis prevalence (64.9%) and the household dogs the lowest (7.9%). Conclusions: This study identifies qPCR as a valuable screening tool because of its high sensitivity, whereas methods using microscopy for cyst identification or cyst wall detection should be used in situations where high specificity is required. G. duodenalis is a prevalent gastro-intestinal parasite in Dutch dogs, especially in dogs living in groups (hunting and shelter dogs) and clinical dogs.

    Exotische ‘sloopplant’ gewoon te koop bij tuincentrum
    Dijk, Chris van - \ 2018
    Genetische manipulatie - Lekker thuis knutselen aan DNA, met je bio-kit
    Beumer, Rijkelt - \ 2017

    Te koop: een doe-het-zelf-pakket voor de genetische knip- en plaktechniek crispr. Volgens de fabrikant is het een werktuig van de DNA-revolutie. Deskundigen waarschuwen voor de bacteriën in het pakket.

    Landschapsecologische systeemanalyse Smoddebos
    Smeenge, H. ; Kieskamp, A.A.M. ; Horsthuis, M.A.P. ; Duijn, B. van; Waal, R. de; Koop, H. ; Essen, E. van; Buijs, R. - \ 2017
    Ede : Coöperatie Unie van Bosgroepen - 96
    Het Smoddebos is een bijzonder bos op leemgrond met een soortenrijke ondergroei die gebonden is aan vochtige gebufferde omstandigheden. Het gebied is eigendom van dhr. Hobbelink en Natuurmonumenten. De kern (Natuurmonumenten) is in 1997 aangewezen als bosreservaat, wat betekent dat er sindsdien geen beheer meer plaats vindt. Gebiedsdeskundigen (o.a. omwonenden) geven op basis van veldwaarnemingen aan dat de rijkdom van de ondergroei in het Smoddebos in de afgelopen dertig jaar is afgenomen. Het is onduidelijk wat de oorzaken zijn van de veranderingen: beheer van het bos en ontwikkeling (in het sluiten) van de boomlaag en successie of een verandering in de abiotische omstandigheden, bijvoorbeeld verdroging. Provincie Overijssel heeft gevraagd om inzicht te geven in de veranderingen in de vegetatie de afgelopen jaren en om uit te zoeken welke oorzaken deze mogelijke veranderingen hebben. Daarom is een landschapsecologische systeemanalyse uitgevoerd, aangevuld met een uitgebreid onderzoek naar flora en vegetatie.
    The intention of North-Western Ethiopian dairy farmers to control mastitis
    Mekonnen, Sefinew Alemu ; Koop, Gerrit ; Lam, Theo J.G.M. ; Hogeveen, Henk - \ 2017
    PLoS ONE 12 (2017)8. - ISSN 1932-6203
    Understanding the intentions of dairy farmers towards mastitis control is important to design effective udder health control programs. We used the Theory of Planned Behavior (TPB) to explore the intentions of North-Western Ethiopian dairy farmers towards implementing non-specified mastitis control measures (nsMCMs) and towards implementing 4 specific MCMs. Face to face interviews were held with 134 dairy farmers to study associations between their intentions and any of three factors (attitude, subjective norm and perceived behavioral control) that, according to the TPB, determine intentions. The majority of the farmers (93%) had a positive intention to implement nsMCMs, whereas a smaller majority of farmers had the intention to implement the specific MCMs to improve udder cleaning (87%), to improve stall hygiene (78%), to improve feeding of cows (76%), and to perform foremilk stripping (74%). Farmers had a more positive attitude, but lower subjective norm and lower perceived behavioural control towards implementing nsMCMs compared with implementing most specific MCMs, although the subjective norms for stall hygiene and perceived behavioural control for improving feeding of cows were also low. Attitude was positively associated with intentions to implement nsMCMs, to improve cleaning of the udders, to improve stall hygiene and to implement foremilk stripping. Both the intention to improve udder cleaning and to implement foremilk stripping, were positively associated to subjective norms towards these MCMs. Our data can help tailor intervention programs aiming to increase the intention of Ethiopian dairy farmers to implement MCMs and thus to improve udder health in this country. We show that such programs should primarily focus on changing attitude and secondarily on improving the farmers’ subjective norms.
    Prevalence of subclinical mastitis and associated risk factors at cow and herd level in dairy farms in North-West Ethiopia
    Mekonnen, Sefinew Alemu ; Koop, G. ; Melkie, S.T. ; Getahun, C.D. ; Hogeveen, H. ; Lam, Theo J.G.M. - \ 2017
    Preventive Veterinary Medicine 145 (2017). - ISSN 0167-5877 - p. 23 - 31.
    Dairy - Ethiopia - Intramammary infection - Mastitis - Risk factor

    Knowledge of mastitis pathogens and their predominance as well as understanding of risk factors are prerequisites to improve udder health in a herd, region or country. In Ethiopia, such information is scarce, despite the fact that mastitis is an important cattle disease in the country. A cross-sectional study that describes prevalence and causative agents of subclinical mastitis (SCM) as well as risk factors at cow and herd level was conducted on 167 dairy farms in North-West Ethiopia. On average, 33% of the quarters and 62% of the cows were California Mastitis Test (CMT) positive, but the within herd quarter level prevalence ranged between 0 and 100%. A total of 1543 milk samples, being 27 quarters that showed signs of CM, 606 CMT positive quarters and 910 CMT negative quarters were cultured, respectively 40%, 67% and 47% was positive on bacteriological culture. Coagulase negative staphylococci (CNS) (31%) followed by Staphylococcus aureus (9%) were the pathogens most frequently isolated. Based on face-to-face questionnaire data, 35 herd level and 13 cow level factors were evaluated for their association with SCM (based on CMT) and with a positive culture for any bacteria, CNS or S. aureus. Cows with a history of CM, of higher parity, >150 days in milk (DIM) and herds with owners that have >10th grade level of education had higher odds of SCM. The odds of being culture positive for any bacteria was higher in cows with ≥25% Holstein Friesian blood level (HBL), >150 DIM, housed on cemented floors, and milked by squeezing rather than stripping. Similarly, the odds of culturing CNS was higher in cows with 25–50% HBL, >150 DIM, and milked by squeezing. Staphylococcus aureus was more often found in cows with a history of CM and in larger herds. Checking the udder for mastitis, feeding cows according to their requirements and allowing calves to suckle the cows were negatively associated with SCM, with culturing any bacteria and with culturing CNS, respectively. Higher odds of SCM and of culturing CNS were found in herds owned by members of a dairy cooperative. In summary, we identified a high prevalence of SCM and intramammary infections with substantial variation between farms, and we found a number of risk factors explaining this variation. The risk factors for mastitis that were identified in this study can form the basis of an udder health control program specific for the dairy industry in North-West Ethiopia.

    Identification of LukPQ, a novel, equid-adapted leukocidin of Staphylococcus aureus
    Koop, Gerrit ; Vrieling, Manouk ; Storisteanu, Daniel M.L. ; Lok, Laurence S.C. ; Monie, Tom ; Wigcheren, Glenn Van; Raisen, Claire ; Ba, Xiaoliang ; Gleadall, Nicholas ; Hadjirin, Nazreen ; Wagenaar, Jaap A. - \ 2017
    Scientific Reports 7 (2017). - ISSN 2045-2322

    Bicomponent pore-forming leukocidins are a family of potent toxins secreted by Staphylococcus aureus, which target white blood cells preferentially and consist of an S- and an F-component. The S-component recognizes a receptor on the host cell, enabling high-affinity binding to the cell surface, after which the toxins form a pore that penetrates the cell lipid bilayer. Until now, six different leukocidins have been described, some of which are host and cell specific. Here, we identify and characterise a novel S. aureus leukocidin; LukPQ. LukPQ is encoded on a 45 kb prophage (Î ▪Saeq1) found in six different clonal lineages, almost exclusively in strains cultured from equids. We show that LukPQ is a potent and specific killer of equine neutrophils and identify equine-CXCRA and CXCR2 as its target receptors. Although the S-component (LukP) is highly similar to the S-component of LukED, the species specificity of LukPQ and LukED differs. By forming non-canonical toxin pairs, we identify that the F-component contributes to the observed host tropism of LukPQ, thereby challenging the current paradigm that leukocidin specificity is driven solely by the S-component.

    Ontwikkelingen in Foodservice : online en beleving creëren nieuwe kansen voor toeleveranciers van agf
    Splinter, G.M. ; Haaster-de Winter, M.A. van - \ 2015
    Wageningen : LEI Wageningen UR - 30
    commerciële catering - food service management - groenten - fruit - gemaksvoedsel - voedselconsumptie - elektronische handel - consumentenvoorkeuren - tendensen - commercial food service - food service management - vegetables - fruit - convenience foods - food consumption - electronic commerce - consumer preferences - trends
    Het voedsellandschap is in beweging. Een ontwikkeling met grote gevolgen voor “vers” en haar toeleveranciers. Voedsel is op steeds meer (verschillende) plaatsen te koop en wordt aangeboden door verschillende aanbieders. GroentenFruit Huis wil de groenten- en fruitsector versterken en de positie van bedrijven verbeteren. LEI Wageningen UR heeft daarom twee ontwikkelingen in de Foodservicemarkt onderzocht: online en beleving. Twee aspecten die het niveau van een individueel bedrijf overstijgen en impact hebben op de bestaande structuur. De uitkomsten zijn aangevuld met informatie over nieuwe ontwikkelingen binnen het thema “gemak”. Hoe moeten de ontwikkelingen worden gezien en wat is het effect ervan op de toeleveranciers van groenten en fruit? En op hun product(en)?
    Robot die grondeieren opraapt binnen enkele jaren op de markt
    Vroegindeweij, Bastiaan - \ 2015

    ‘Robot die grondeieren opraapt binnen enkele jaren op de markt’

    Wageningen, woensdag 23 december 2015

    Bastiaan Vroegindeweij verwacht dat zijn robot die automatisch en zelfstandig grondeieren in een leg- of vermeerderingsstal op kan rapen binnen enkele jaren te koop is.

    „Momenteel kost het een pluimveehouder elke dag al gauw eentwee uur per stal om grondeieren te rapen”, zegt Vroegindeweij, promovendus bij Farm technology. Dat is geen leuk werk en daarom ontwikkelde hij een robot die automatisch grondeieren kan rapen.

    De promovendus verwacht over 1,5 jaar een prototype te hebben, dat hij daarna kan testen in een leghennenstal. „Als het prototype goed werkt dan kan ik meer robots laten bouwen voor pluimveehouders”, vertelt hij. „Als alles naar wens verloopt, verwacht ik dat pluimveehouders de robot binnen twee tot drie jaar kunnen kopen.”

    Technologie zelfrijdende auto

    Vroegindeweij gebruikt dezelfde technologie als zelfrijdende auto’s. De robot bepaalt zijn locatie aan de hand van eigen bewegingen en het scannen van de omgeving met een laser. Ondertussen ‘zoekt’ de robotsoftware op de camerabeelden naar eieren.

    „De testrobot kan al eieren oprapen. Al moet dit nog verder worden verbeterd. Bij fel licht ziet hij bijvoorbeeld eieren over het hoofd en ook bleef niet elk ei heel”, zegt Vroegindeweij.

    Kippen wennen er snel aan

    „Kippen wennen ontzettend snel aan de robot”, vertelt Vroegindeweij. Bovendien een hoeft een pluimveehouder veel minder vaak zelf de stal in, en kan hij die momenten beter aan zijn eigen schema aanpassen. „Juist de soms onvoorspelbare bewegingen van mensen zouden meer stress veroorzaken”, geeft de promovendus aan.

    Het rapen van eieren is overigens slechts het begin. Pluimveehouders hebben met hun robot constant ‘ogen en oren’ tussen de kippen rondrijden om te letten op zieke dieren. Ook kan de luchtvochtigheid en temperatuur heel lokaal worden bijgehouden.

    „Ik kan zo dertig, veertig toepassingen bedenken”, vertelt Vroegindeweij. Maar hij verwacht dat de raapfunctie genoeg motivatie zal zijn voor boerenlegpluimveehouders. Voor de vleessector is juist het idee van oren en ogen meer relevant.

    Op zoek naar een partner

    Vroegindeweij zoekt nu nog een partner om zijn robot op de markt te zetten. Hij schat dat de robot om en nabij de 50.000 euro moet kosten. Een pluimveehouder kan deze terugverdienen doordat hij tijd bespaart.

    „Op een bedrijf met 40.000 hennen is hij gemiddeld 1 tot 2 uur per dag bezig met grondeieren rapen.” Wekelijks kan hij dan 7 tot 14 uur besparen en jaarlijks 365 tot 730 uur. De terugverdientijd ligt dan op 2,75 tot 5,5 jaar bij 25 euro per uur voor arbeid.

    Tekst:Tom Schotman

    Beeld:Bastiaan Vroegindeweij

    Protease activity measurement in milk as a diagnostic test for clinical mastitis in dairy cows
    Koop, G. ; Werven, T. van; Roffel, S. ; Hogeveen, H. ; Nazmi, K. ; Bikker, F.J. - \ 2015
    Journal of Dairy Science 98 (2015)7. - ISSN 0022-0302 - p. 4613 - 4618.
    Cow - Mastitis - Milk - Protease

    Due to the increasing use of automated milking systems, automated detection of clinical mastitis is becoming more important. Various in- or on-line diagnostic tests are in use, but generally suffer from false mastitis alerts. In this study, we explored a new diagnostic approach based on measurement of protease activity using fluorogenic protease substrates, which can be performed on site, at high speed, and at low costs. Samples from cows with clinical mastitis submitted for bacteriological culture at the University Farm Animal Practice were collected during several months and kept at -20°C until protease activity measurement. A reference set of milk samples from clinically healthy cows were collected on 9 different farms and were tested for protease activity directly and after freezing at -20°C to allow for comparison with the samples from clinical cases. The protease activity in mastitic milk samples was significantly higher than in samples from healthy animals. Based on 71 clinical mastitis samples and 180 milk samples from clinically healthy quarters, the area under the receiver-operating characteristic curve was estimated to be between 0.88 and 0.90, and at a threshold of 38 fluorescence per minute the test had a specificity of 0.99 at a sensitivity of 0.58. Protease activity measured in fresh milk from clinically healthy cows was significantly associated with somatic cell count and parity, but not with electrical conductivity, whereas protease activity in milk that had been frozen was statistically significantly associated with all 3 parameters. This study indicates that protease activity measurement as a stand-alone test can be used for detecting mastitis samples, using milk samples that have been frozen. Because protease activity acts in part on a different biological mechanism than somatic cell count or electrical conductivity, this test may increase the accuracy of mastitis diagnosis in combination with currently available in- or on-line tests in automated milking systems.

    Seroprevalence and associated risk factors of important pig viral diseases in Bhutan
    Monger, V.R. ; Stegeman, J.A. ; Koop, G. ; Dukpa, K. ; Tenzin, T. ; Loeffen, W.L.A. - \ 2014
    Preventive Veterinary Medicine 117 (2014)1. - ISSN 0167-5877 - p. 222 - 232.
    classical swine-fever - influenza-a h1n1 - vaccination policy - antigenic drift - virus - infection - diagnosis - prrs
    A cross-sectional serological study was conducted in Bhutan between October 2011 and February 2012 to determine the prevalence of antibodies to classical swine fever virus (CSFV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), swine influenza virus (SIV) subtype H1N1 and Aujeszky's disease virus (ADV). Furthermore, risk factors for the seropositive status were investigated. Antibodies to SIV, subtype H1N1 (likely pandemic H1N1 2009) were detected in 49% of the pigs in the government farms, and 8% of the village backyard pigs. For PCV2, these percentages were 73% and 37% respectively. For CSFV, the percentages were closer together, with 62% and 52% respectively. It should be taken into consideration that vaccination of piglets is routine in the government herds, and that piglets distributed to backyard farms are also vaccinated. No direct evidence of CSFV infections was found, either by clinical signs or virus isolation. Antibodies to PRRSV and Aujeszky's disease, on the other hand, were not found at all. Risk factors found are mainly related to practices of swill feeding and other biosecurity measures. For CSFV, these were swill feeding (OR = 2.25, 95% CI: 1.01–4.99) and contact with neighbour's pigs (OR = 0.31, 95% CI: 0.13–0.75). For PCV2 this was lending of boars for local breeding purposes (OR = 3.30, 95% CI: 1.43–7.59). The results of this study showed that PCV2 and SIV infections are important in pigs in Bhutan and thus appropriate control strategies need to be designed and applied which could involve strict regulation on the import of live pigs and vaccination against these diseases.
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