Staff Publications

Staff Publications

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    '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.

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Identifying groundwater recharge pathways in the Moscow sub-basin
Candel, J.H.J. ; Brooks, E.S. ; Verhoeff, Eric ; Dobre, Mariana ; Sanchez-Murillo, Ricardo ; Grader, Jr., George W. ; Dijksma, R. - \ 2016
Continual groundwater decline over the last 80 years in the Moscow-Pullman basin is motivating communities to explore a wide range of strategies ranging from reservoir development to direct injection to aquifers to ensure a sustainable regional water supply. Historic pumping records indicate the shallow Wanapum aquifer in the Moscow region does receive recharge however it is less certain that the deeper Grand Ronde aquifer is receiving any significant recharge. Moreover there is not a clear consensus in the region of the location of the major aquifer recharge flow paths. In this study we used both distributed hydrologic modeling based on detailed soil mapping and stable isotope tracers to explore and evaluate potential groundwater recharge pathways in the Moscow sub-basin. Modelling results indicate that subsurface water flow off the forested granitics in eastern margin of the sub-basin is likely a significant source of recharge. Biweekly water samples taken from 22 wells and 2 springs and high frequency streamflow and precipitation samples collected over a two year period throughout the Moscow sub-basin were analyzed for stable isotopes of hydrogen and oxygen. Frequency analysis of these stable isotope data suggest the some wells are receiving recharge. Furthermore many of these wells exist on the eastern margin of the sub-basin lending further support to the hypothesis that this region should be considered to be a critical ground recharge zone.
Grip op medicijnresten in ons water : Eindrapportage
Diels, J. ; Muis, J. ; Verhoeff, A. ; Vliet, B. van; Hendriksen, A. ; Wijn, G. - \ 2015
Zwolle : Waterschap Groot Salland - 64
Getting a grip on drug residues in our waters : A report on a source-oriented approach to drug residues in our waters
Diels, J. ; Muis, J. ; Verhoeff, A. ; Vliet, B.J.M. van; Hendriksen, A. ; Wijn, G. - \ 2015
Zwolle : Water Authority Groot Salland - 63 p.
Campylobacter jejuni: een hardnekkige volhouder (interview met L. Verhoeff-Bakkenes)
Verhoeff-Bakkenes, L. - \ 2012
campylobacter jejuni - growth - survival - infectivity - bacterial diseases - risk assessment - food microbiology
Niet alleen kip geeft ziekte door Campylobacter
Verhoeff-Bakkenes, L. - \ 2012
Campylobacter jejuni: exposure assessment and hazard characterization : growth, survival and infectivity of Campylobacter jejuni
Verhoeff-Bakkenes, L. - \ 2012
University. Promotor(en): Marcel Zwietering, co-promotor(en): Rijkelt Beumer; R. de Jonge. - [S.l.] : s.n. - ISBN 9789461731241 - 144
campylobacter jejuni - groei - overleving - infectiviteit - bacterieziekten - risicoschatting - voedselmicrobiologie - growth - survival - infectivity - bacterial diseases - risk assessment - food microbiology

Campylobacter jejuni, a small, curved or spirally shaped highly motile microorganism, is identified as a major cause of bacterial gastroenteritis throughout the world. Serious complications such as the Guillain-Barré syndrome and reactive arthritis might occasionally follow infection. In this thesis data were generated in the fields of hazard characterization and exposure assessment, which were used to identify risk factors for Campylobacter.

Although C. jejuni is generally seen as an obligate micro-aerophile, in this thesis it was shown that it can grow aerobically in the presence of pyruvate, and growth might also be possible in the presence of other antioxidants. However, as result of the strict minimal growth temperature (30ºC), C. jejuni is still assumed to be generally unable to grow in foods and therefore growth is not considered as a large risk for campylobacteriosis.

C. jejunican, and does, survive effectively for long periods of time under non-growing conditions in various environments. Temperature is the most influencing factor in survival and survival will be optimal at low temperatures (around 4ºC). As many foods are stored chilled, this will prolong the survival of C. jejuni. Furthermore survival is enhanced at low oxygen conditions, as often present in packaged foods. While the effects of environmental conditions on the survival of C. jejuni have been studied extensively, the knowledge of the effect of environmental factors on the infectivity was scarce. Therefore, the effect of environmental conditions (temperature, medium and atmosphere) on both the survival of C. jejuni and the infectivity of the surviving cells was investigated. We revealed that culturability and infectivity are linearly related. Furthermore, our study on the effect on the infectivity of adding nonculturable C. jejuni cells to culturable cell suspensions, showed nonculturable cells not to be infective (in vitro). Therefore, absence of culturable C. jejuni cells indicates that a product can be regarded as representing a very low risk with respect to campylobacteriosis.

Food products can be contaminated with Campylobacter during production or afterwards at the consumer’s home. Once contaminated the risk is high that Campylobacter will survive on food products until the moment of consumption, except if the product undergoes an elimination step during preparation, such as heating. The growth requirements for Campylobacter are met in the gastrointestinal tract of warm-blooded animals. As a result especially products of animal origin, like chicken meat and raw milk, are often contaminated by Campylobacter, but also products of non-animal origin, like vegetables and fruits, can be contaminated. Within the exposure assessment cross-contamination in the home, the importance of raw vegetables and fruits as a risk factor for Campylobacter, and the relative importance of chicken meat, raw milk and raw vegetables and fruits were studied.

The effect of different cross-contamination routes during the preparation of a chicken fruit salad was investigated. It was shown that the mean transfer rate by cross-contamination was 0.12% of the initial number of C. jejunion the chicken fillet, and that the different tested cross-contamination routes; cutlery, cutting board and hands, were equally important. The high prevalence and concentration of C. jejuni on chicken meat, the high percentage of consumers who exhibit improper hygienic and cleaning behaviour, and the significant transfer of Campylobacter during improper food preparation, indicate cross-contamination from raw foods, such as chicken, to other ready-to-eat foods as a large risk factor for Campylobacter infection.

Fresh produce can become contaminated with C. jejuni during cultivation or processing. Especially vegetables and fruits which are eaten raw may present a risk. In this thesis Dutch data on the prevalence of Campylobacter on raw vegetables and fruits were newly analysed. Thirteen of the 5640 vegetable and fruit samples were Campylobacter positive, resulting in a prevalence of 0.23% (95% confidence interval (Cl): 0.12-0.39%). The prevalence on packaged products was significantly higher than on unpackaged products.

Finally, the newly acquired data and quantitative literature data on the prevalence and concentration of Campylobacter entering the consumer phase were summarized for three food groups; vegetables and fruit, chicken, and raw milk. These data were used in a quantitative risk assessment model to estimate the exposure and the number of illnesses as result of the consumption of these foods and to compare their relative importance. The prevalence and concentration are low on raw vegetables and fruit, but the quantity of raw vegetables and fruits consumed is very high. In contrast, raw chicken and raw milk show relative high prevalence and concentration levels, but the consumption is low. Despite the differences in parameters, the exposure calculated out of the combination of parameters indicates all these three foods as high risk factors for Campylobacter. So foods which are not heavily contaminated with Campylobacter, but are consumed in large quantities can constitute a similar high risk on Campylobacter infection as foods which are consumed in small quantities but are heavily contaminated with Campylobacter.

Consumption of raw vegetables and fruits: a risk factor for Campylobacter infections
Verhoeff-Bakkenes, L. ; Jansen, H.A.P.M. ; Veld, P.H. in 't; Beumer, R.R. ; Zwietering, M.H. ; Leusden, F.M. van - \ 2011
International Journal of Food Microbiology 144 (2011)3. - ISSN 0168-1605 - p. 406 - 412.
eat salad vegetables - fresh produce - microbiological quality - retail establishments - organic vegetables - public-health - new-zealand - jejuni - survival - foods
The purpose of this study was to determine the prevalence of Campylobacter in fresh vegetables and fruits at retail level in the Netherlands, and to estimate its implications on the importance of vegetables and fruits as risk factor for campylobacteriosis. Thirteen of the 5640 vegetable and fruit samples were Campylobacter positive, resulting in a prevalence of 0.23% (95% confidence interval (Cl): 0.12–0.39%). The prevalence of packaged products (0.36%, 95% Cl: 0.17–0.66) was significantly higher than of unpackaged products (0.07; 95% Cl: 0.01–0.27). No statistical differences were found between seasons. Combining the mean prevalence found in this study with data on the consumption of vegetables and fruits, an exposure of 0.0048 campylobacters ingested per person per day in the Netherlands by transmission via vegetables and fruits, was calculated. This exposure, as input in a Beta-Poisson dose–response model, resulted in an estimated number of 5.3 × 105 cases of infection with Campylobacter per year for the whole Dutch population. This constitutes the consumption of raw vegetables and fruits, especially when packaged, to be a risk factor for Campylobacter infections
Campylobacter jejuni: a study on environmental conditions affecting culturability and in vitro adhesion/invasion
Verhoeff-Bakkenes, L. ; Hazeleger, W.C. ; Jonge, R. de; Zwietering, M.H. - \ 2009
Journal of Applied Microbiology 106 (2009)3. - ISSN 1364-5072 - p. 924 - 931.
coccoid forms - survival - temperature - cells - invasion - chicks - growth - water - colonization - mechanisms
Aims: Nongrowing cultures of Campylobacter jejuni lose their culturability. It is unclear whether this loss in culturability also affects their ability to interact with host cells. The purpose of this study was to determine the relevance of the number of culturable cells to the ability to adhere/invade in Caco-2 cells. Methods and Results: For C. jejuni C356, culturability and adhesion/invasion were monitored in time (days) under different storage conditions (temperature, medium, atmosphere). Decrease rates of both culturability and adhesion/invasion were dependent on the conditions used, but the number of adhering/invading cells per culturable cell was not affected by the environmental conditions. Furthermore five strains were monitored at one condition. The culturability and adhesion/invasion decrease rates did not significantly differ per strain; however the number of adhering/invading cells per culturable cell was strain dependent. Conclusions: Culturability and adhesion/invasion of C. jejuni are linearly related. The number of adhering/invading cells per culturable C. jejuni cell is strain dependent, but is not affected by environmental conditions. Significance and Impact of the Study: It was shown that the number of culturable cells is a good measure for the in vitro adhesion/invasion of. C. jejuni.
Lack of response of INT-407 cells to the presence of non-culturable Campylobacter jejuni
Verhoeff-Bakkenes, L. ; Hazeleger, W.C. ; Zwietering, M.H. ; Jonge, R. de - \ 2008
Epidemiology and Infection 136 (2008)10. - ISSN 0950-2688 - p. 1401 - 1406.
epithelial-cells - invasion - interleukin-8 - recovery - chicks - colonization - microtubules - mechanisms - virulence - proteins
Many contradictory articles on the infectivity of non-culturable Campylobacter jejuni can be found. We studied the effect of non-culturable C. jejuni in an in vitro assay. To prevent the potential effect of a few culturable bacteria in the non-culturable suspension, INT-407 cells, which mimic the outer cell layer in the small intestines, were exposed to culturable C. jejuni suspensions with or without non-culturable C. jejuni. The number of bacteria adhering to and/or invading INT-407 cells and the IL-8 secretion were measured. No differences were found between bacterial suspensions with or without non-culturable C. jejuni added. These findings show that non-culturable C. jejuni do not adhere to or invade INT-407 cells and do not induce an immune response. As previous studies showed a correlation between the used in vitro assays and the effect in vivo, our study strongly suggests that culturability is a good indicator of the risk for C. jejuni infection.
Quantification of Campylobacter jejuni cross-contamination via hands, cutlery, and cutting board during preparation of a chicken fruit salad
Verhoeff-Bakkenes, L. ; Beumer, R.R. ; Jonge, R. de; Leusden, F.M. van; Jong, A.E.I. de - \ 2008
Journal of Food Protection 71 (2008)5. - ISSN 0362-028X - p. 1018 - 1022.
food-handling practices - foodborne pathogens - domestic kitchen - united-states - risk-factors - survival - infection - safety - salmonella - surfaces
Using artificially contaminated chicken, the quantitative overall effect of Campylobacter jejuni cross-contamination, either via cutlery, cutting board, or hands, on the microbiological quality of a chicken salad was tested to identify the most critical transfer route. The end contamination level of salads prepared according to different scenarios, with or without cross-contamination, was compared. It was shown that the mean transfer rate calculated for all salads prepared allowing cross-contamination was 0.12% of the initial number of C. jejuni on the chicken fillet (8.8 ± 0.2 log CFU). The difference in calculated transfer rates for the tested cross-contamination routes was not significantly different (P > 0.05). The prevention of cross-contamination by replacing cutlery and cutting board after handling raw chicken and the prevention of hand contact resulted in considerably reduced end contamination levels (
Pyruvate relieves the necessity of high induction levels of catalase and enables Campylobacter jejuni to grow under fully aerobic conditions
Verhoeff-Bakkenes, L. ; Arends, A.P. ; Snoep, J.L. ; Zwietering, M.H. ; Jonge, R. de - \ 2008
Letters in Applied Microbiology 46 (2008)3. - ISSN 0266-8254 - p. 377 - 382.
fetus subsp jejuni - superoxide-dismutase - hydrogen-peroxide - escherichia-coli - microaerophilic nature - foodborne pathogen - oxygen - metabolism - survival - aerotolerance
Aims: Several cases of campylobacteriosis reported worldwide seemingly conflict with the strict growth requirements and sensitivity to environmental stress of Campylobacter jejuni. In this study, the need for a micro-aerobic environment [dissolved oxygen tension (DOT): 0·1¿90%; 100% air saturation)] and the adaptive responses to oxygen stress were studied. Methods and Results: The growth of C. jejuni in continuous culture was assessed under different DOT in the presence or absence of pyruvate. In a medium without pyruvate, continuous cultures of C. jejuni showed typically micro-aerobic behaviour and cells were unable to grow under fully aerobic conditions. However in the presence of pyruvate (25 mmol l¿1), continuous cultures of C. jejuni were able to grow in a broad DOT range, varying from 0·1% to at least 90%, and the catalase activity was decreased. Conclusions: Addition of pyruvate results in the decrease in the concentration of hydrogen peroxide, which enables C. jejuni to grow aerobically. Significance and Impact of the Study: New information on the oxidative physiology of C. jejuni and its ability to grow aerobically in media supplemented with pyruvate is presented
Cross-contamination in the kitchen: effect of hygiene measures
Jong, A.E.I. de; Verhoeff-Bakkenes, L. ; Nauta, M.J. ; Jonge, R. de - \ 2008
Journal of Applied Microbiology 105 (2008)2. - ISSN 1364-5072 - p. 615 - 624.
food-handling practices - foodborne pathogens - campylobacter-jejuni - domestic kitchen - united-states - stainless-steel - survival - chicken - safety - risk
Aims: To determine the effect of hygiene measures on cross-contamination of Campylobacter jejuni at home and to select a safe tracer organism for C. jejuni. Methods and Results: Comparative tests were conducted with nonpathogenic Escherichia coli and Lactobacillus casei and L. casei was chosen as the safe tracer organism. Salads containing chicken breast fillet contaminated with a known number of C. jejuni and L. casei were prepared according to different cross-contamination scenarios and contamination levels of salads were determined. Cross-contamination could be strongly reduced when cleaning cutting board and cutlery with hot water (68°C), but generally was not prevented using consumer-style cleaning methods for hands and cutting board. Conclusions: Dish-washing does not sufficiently prevent cross-contamination, thus different cutting boards for raw meat and other ingredients should be used and meat¿hand contact should be avoided or hands should be thoroughly cleaned with soap. Lactobacillus casei can be used as a safe tracer organism for C. jejuni in consumer observational studies. Significance and Impact of the Study: Cross-contamination plays an important role in the transmission of food-borne illness, especially for C. jejuni. This study delivers suitable data to quantitatively assess the risk of campylobacteriosis caused by cross-contamination and it shows the effect of different preventive hygiene measures.
Assessing the repeatability and reproducibility of the Leg Score: a Dutch Claw Health Scoring System for dairy cattle
Holzhauer, M. ; Middelesch, H. ; Bartels, C.J. ; Frankena, K. ; Verhoeff, J. ; Noordhuizen-Stassen, E.N. ; Noordhuizen, J.P.T.M. - \ 2005
Tijdschrift voor Diergeneeskunde 130 (2005)14-15. - ISSN 0040-7453 - p. 440 - 443.
melkveehouderij - klauwen - hoeven - afknippen - herhaalbaarheid - timing - dierverzorging - observatie - dairy farming - claws - hooves - clipping - repeatability - care of animals - observation - reproductive-performance - floor systems - lameness - cows - associations - disorders - disease - lesions - traits - herds
The optimal moment for trimming the claws of all dairy cows in a herd was investigated by assessing the external rotation of the hind claws of individual cows relative to the spinal column. This leg score consisted of three independent descriptors: 1 (good/ normal), 2 (moderately deviant), and 3 (severely deviant). This study assessed the repeatability and the reproducibility of the leg score system, and the consistency of the advice given subsequently about trimming of the hind claws of all cows in the herd. Repeatability was assessed for 52 cows that were scored twice on the same day by 11 observers; the kappa value ranged from 0.17 to 0.66 (mean: 0.36). The probability of the same result for both assessments ranged from 0.49 to 0.80 (mean: 0.61). Claw trimming was advised if at least 20% of the cows had a leg score of 3. On the basis of the scores, 3 observers consistently advised trimming of the hind claws of all the cows in the herd, and 6 observers consistently advised against the need for trimming in the short term; 2 observers had an inconsistent advice. The reproducibility of the scoring system was assessed in two dairy herds (62 and 50 cows). Eight observers evaluated the leg score of the cows of both herds on the same day. The mean kappa value of the leg score for all pairs of different observers (A-B, A-C etcetera) was 0.24 [-0.08-0.49]. In conclusion, the leg score is not a reliable method for determining the optimal moment for claw trimming in dairy cattle. The reasons for the inconsistent observations require further investigation
The optimal moment for trimming the claws of all dairy cows in a herd was investigated by assessing the external rotation of the hind claws of individual cows relative to the spinal column. This leg score consisted of three independent descriptors: 1 (good/normal), 2 (moderately deviant), and 3 (severely deviant). This study assessed the repeatability and the reproducibility of the leg score system, and the consistency of the advice given subsequently about trimming of the hind claws of all cows in the herd. Repeatability was assessed for 52 cows that were scored twice on the same day by 11 observers; the kappa value ranged from 0.17 to 0.66 (mean: 0.36). The probability of the same result for both assessments ranged from 0.49 to 0.80 (mean: 0.61). Claw trimming was advised if at least 20 % of the cows had a leg score of 3. On the basis of the scores, 3 observers consistently advised trimming of the hind claws of all the cows in the herd, and 6 observers consistently advised against the need for trimming in the short term; 2 observers had an inconsistent advice. The reproducibility of the scoring system was assessed in two dairy herds (62 and 50 cows). Eight observers evaluated the leg score of the cows of both herds on the same day. The mean kappa value of the leg score for all pairs of different observers (A-B, A-C etcetera) was 0.24 [-0.08-0.49]. In conclusion, the leg score is not a reliable method for determining the optimal moment for claw trimming in dairy cattle. The reasons for the inconsistent observations require further investigation.
Herd-level diagnosis for Salmonella enterica subsp enterica serovar Dublin infection in bovine dairy herds
Veling, J. ; Barkema, H.W. ; Schans, J. van de; Zijderveld, F.G. van; Verhoeff, J. - \ 2002
Preventive Veterinary Medicine 53 (2002)39479. - ISSN 0167-5877 - p. 31 - 42.
linked-immunosorbent-assay - california dairies - cattle - milk - antibodies - prevalence - tests
Herd-level sensitivities of bacteriological and serological methods were compared in 79 bovine dairy herds, recently infected with Salmonella enterica subsp. enterica serovar Dublin. All farms experienced clinical signs of salmonellosis for the first time and had no history of vaccination against salmonellosis. At the start of the study, infection with serovar Dublin was confirmed with at least one positive bacteriologic culture for serovar Dublin from a clinical case (gold standard for herd infection). Bacteriological culture was done on samples of dung-pits, drinking water, bulk-milk filters, and faeces of animals with current or earlier clinical signs of salmonellosis. Blood samples of all animals and bulk-milk samples were tested using an ELISA. Herd-level sensitivity (HSe) of culture of dung-pits, drinking water, bulk-milk filters, and faeces of animals with current or earlier signs of salmonellosis was 45, 5, 7, and 38%, respectively. HSe for serology of all animals was 100%. If blood samples of all calves 4¿6 months old were examined, at least one calf was seropositive on 91% of the infected farms. If serology was performed on samples of animals with current or earlier signs of salmonellosis, at least one animal was seropositive on 80% of the infected farms. HSe for bulk-milk samples was 54%. However, if clinical signs of salmonellosis were observed only in lactating animals, sensitivity of bulk-milk serology was 79%. Interesting combinations of methods were the combination of serology of bulk milk with either serology of animals with current or earlier signs of salmonellosis (HSe=91%), or serology of all calves of 4¿6 months old (HSe=99%).
Onverwachte omslag in BVD-status high-techbedrijf
Bloemert, J. ; Verhoeff, K. ; Kamp, A. van der - \ 2002
Praktijkkompas. Rundvee 16 (2002)4. - ISSN 1570-8586 - p. 20 - 21.
melkveehouderij - melkvee - diergezondheid - pestivirus - rundveeziekten - pathogeen eliminatie - certificering - infecties - infectieziekten - ziekteoverdracht - ziektebestrijding - melkveebedrijven - proefbedrijven - demonstratiebedrijven, landbouw - proefboerderijen - dairy farming - dairy cattle - animal health - cattle diseases - pathogen elimination - certification - infections - infectious diseases - disease transmission - disease control - dairy farms - pilot farms - demonstration farms - experimental farms
Hoe nu verder te handelen om de vrije status terug te krijgen?
Campylobacteriose in Nederland : risico's en interventiemogelijkheden
Beumer, R.R. ; Boer, E. de; Bogaardt, M.J. ; Duim, B. ; Duynhoven, Y.T.H.P. van; Evers, E.G. ; Havelaar, A.H. ; Horne, P. van; Jacobs-Reitsma, W.F. ; Leusden, F.M. van; Mevius, D.J. ; Nauta, M.J. ; Pelt, W. van; Poppe, K.J. ; Schijven, J.F. ; Stegeman, H.J. ; Verhoeff-Bakkenes, L. ; Wagenaar, J.A. ; Wit, A. de; Wit, M.A.S. de - \ 2002
Bilthoven : RIVM (RIVM rapport 250911001) - 159
volksgezondheid - voedselinspectie - campylobacteriose - campylobacter - risicofactoren - nederland - public health - food inspection - campylobacteriosis - risk factors - netherlands
Effects of bovine respiratory disease on the productivity of dairy heifers quantified by experts
Fels-Klerx, H.J. van der; Saatkamp, H.W. ; Verhoeff, J. ; Dijkhuizen, A.A. - \ 2002
Livestock Production Science 75 (2002). - ISSN 0301-6226 - p. 157 - 166.
The aim of the current study was to obtain expert data on the effects on productivity (EPs) associated with bovine respiratory disease (BRD) in dairy heifers. Expert knowledge on the EPs of BRD was elicited because a complete insight into these effects was not available from the literature. The experts' assessments of the EPs were quantified, applying the computerised ELI technique, by means of subjective probability density functions (PDFs). For each EP, the individual experts' PDFs were aggregated, hereby weighting the experts according to their expertise, to obtain a single weighted distribution per parameter. Results indicated that mortality following severe pneumonia in heifers <3 months was assessed to be increased by nearly 20ørange 16–24Ž Body weight of diseased heifers was estimated to be reduced by 10 kg (range 2–18 kg) at 3 months, up to 29 kg (range 23–36 kg) at 14 months. Furthermore, pneumonia was assessed to delay first calving age with half a month (range 0.1–0.9 months), and to reduce first lactation milk production by about 2ø150 kg, range 40–250 kg). BRD outbreaks in heifers 3 months were also estimated to reduce body weight at 14 months with approximately 30 kg (range 11–54 kg). The resulting EPs following BRD outbreaks were found to be less severe, and only occasionally as detrimental as the EPs associated with early pneumonia. It was concluded that the expert data obtained provide valuable information for economic decision-making in dairy practise.
'Inventarisatie van het onderzoek naar slijtende koeien.'
Meijer, G.A.L. ; Bouma, A. ; Verhoeff, J. - \ 2001
Unknown Publisher
Inventarisatie van het onderzoek naar slijtende koeien
Meijer, G.A.L. ; Bouma, A. ; Verhoeff, K. - \ 2001
In: Jaarboek Koninklijke maatschappij voor diergeneeskunde 2000
Mogelijkheden voor nader onderzoek naar de slijterproblematiek. [Chronic wasting of dairy cows: a review of research]
Meijer, G.A.L. ; Bouma, A. ; Verhoeff, J. - \ 2001
Tijdschrift voor Diergeneeskunde 126 (2001). - ISSN 0040-7453 - p. 223 - 225.
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