Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    '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 

Records 1 - 20 / 3408

  • help
  • print

    Print search results

  • export
    A maximum of 250 titles can be exported. Please, refine your queryYou can also select and export up to 30 titles via your marked list.
  • alert
    We will mail you new results for this query: q=jong de
Check title to add to marked list
Transmission of digital dermatitis in dairy cattle: population dynamics and host quantitative genetics
Biemans, Floor - \ 2018
University. Promotor(en): Mart de Jong, co-promotor(en): Piter Bijma. - Wageningen : Wageningen University - ISBN 9789463437639 - 204
Intact DNA purified from flow-sorted nuclei unlocks the potential of next-generation genome mapping and assembly in Solanum species
Gaiero, Paola ; Šimková, Hana ; Vrána, Jan ; Santiñaque, Federico F. ; López-Carro, Beatriz ; Folle, Gustavo A. ; Belt, José van de; Peters, Sander A. ; Doležel, Jaroslav ; Jong, Hans de - \ 2018
MethodsX 5 (2018). - ISSN 2215-0161 - p. 328 - 336.
BioNano genome mapping - Flow sorting - Genome finishing - HMW DNA isolation
Next-generation genome mapping through nanochannels (Bionano optical mapping) of plant genomes brings genome assemblies to the ‘nearly-finished’ level for reliable and detailed gene annotations and assessment of structural variations. Despite the recent progress in its development, researchers face the technical challenges of obtaining sufficient high molecular weight (HMW) nuclear DNA due to cell walls which are difficult to disrupt and to the presence of cytoplasmic polyphenols and polysaccharides that co-precipitate or are covalently bound to DNA and might cause oxidation and/or affect the access of nicking enzymes to DNA, preventing downstream applications. Here we describe important improvements for obtaining HMW DNA that we tested on Solanum crops and wild relatives. The methods that we further elaborated and refined focus on • Improving flexibility of using different tissues as source materials, like fast-growing root tips and young leaves from seedlings or in vitro plantlets.• Obtaining nuclei suspensions through either lab homogenizers or by chopping.• Increasing flow sorting efficiency using DAPI (4′,6-diamidino-2-phenylindole) and PI (propidium iodide) DNA stains, with different lasers (UV or 488 nm) and sorting platforms such as the FACSAria and FACSVantage flow sorters, thus making it appropriate for more laboratories working on plant genomics.The obtained nuclei are embedded into agarose plugs for processing and isolating uncontaminated HMW DNA, which is a prerequisite for nanochannel-based next-generation optical mapping strategies.
Origin and Processing Methods Slightly Affect Allergenic Characteristics of Cashew Nuts (Anacardium occidentale)
Reitsma, Marit ; Bastiaan-Net, Shanna ; Sijbrandij, Lutske ; Weert, Evelien de; Sforza, Stefano ; Gerth van Wijk, Roy ; Savelkoul, Huub F.J. ; Jong, Nicolette W. de; Wichers, Harry J. - \ 2018
Journal of Food Science 83 (2018)4. - ISSN 0022-1147 - p. 1153 - 1164.
2D electrophoresis - Anacardium occidentale - cashew - in vitro gastric digestion
The protein content and allergen composition was studied of cashews from 8 different origins (Benin, Brazil, Ghana, India, Ivory Coast, Mozambique, Tanzania, Vietnam), subjected to different in-shell heat treatments (steamed, fried, drum-roasted). On 2D electrophoresis, 9 isoforms of Ana o 1, 29 isoforms of Ana o 2 (11 of the acidic subunit, 18 of the basic subunit), and 8 isoforms of the large subunit of Ana o 3 were tentatively identified. Based on 1D and 2D electrophoresis, no difference in allergen content (Ana o 1, 2, 3) was detected between the cashews of different origins (P > 0.5), some small but significant differences were detected in allergen solubility between differently heated cashews. No major differences in N- and C-terminal microheterogeneity of Ana o 3 were detected between cashews of different origins. Between the different heat treatments, no difference was detected in glycation, pepsin digestibility, or IgE binding of the cashew proteins.
Analysis for low-molecular-weight carbohydrates is needed to account for all energy-contributing nutrients in some feed ingredients, but physical characteristics do not predict in vitro digestibility of dry matter
Navarro, D.M.D.L. ; Bruininx, E.M.A.M. ; Jong, L. de; Stein, H.H. - \ 2018
Journal of Animal Science 96 (2018)2. - ISSN 0021-8812 - p. 532 - 544.
Energy - In vitro digestibility - Physicochemical characteristics - Total dietary fiber
An experiment was conducted to quantify nutrient and fiber fractions of feed ingredients and to determine in vitro apparent ileal digestibility (IVAID) and in vitro apparent total tract digestibility (IVATTD) of DM and OM in each ingredient. Ten ingredients that vary in fiber concentration and composition were used: corn, wheat, soybean meal (SBM), canola meal, distillers dried grains with solubles (DDGS), corn germ meal, copra expellers, sugar beet pulp (SBP), synthetic cellulose (SF), and pectin. Correlations between chemical and physical characteristics of ingredients and IVAID and IVATTD of DM and OM were determined. The physical characteristics measured included bulk density, water-binding capacity (WBC), swelling, and viscosity. The analyzed GE was compared with values for GE calculated from all energy-contributing components. Results indicated that the analyzed chemical composition of most ingredients added to 100% or greater, except for DDGS, SBP, and SF, where nutrients added to only 94.29%, 88.90%, and 96.09%, respectively. The difference between the sum of the calculated GE of the analyzed components and the analyzed GE of the ingredients ranged from −2.25 MJ/kg in DDGS to 1.74 MJ/kg in pectin. No correlation was observed between swelling, WBC, or viscosity and IVAID or IVATTD of DM or OM. The concentration of insoluble dietary fiber (IDF) and total dietary fiber (TDF) was negatively correlated (P < 0.05) with IVAID and IVATTD of DM and OM. There was a tendency for NDF (r = −0.60) and ADF (r = −0.61) to be negatively correlated (P < 0.10) with IVAID of DM. However, no correlation was observed between the concentration of CP, GE, acid-hydrolyzed ether extract, lignin, or soluble dietary fiber and IVAID and IVATTD of DM and OM. The stronger correlations between IDF, TDF, and insoluble non-starch polysaccharides and IVAID and IVATTD of DM and OM than between ADF and NDF and IVAID and IVATTD of DM and OM indicate that the concentration of TDF in feed ingredients is a better predictor of the digestibility of DM and OM than values for NDF and ADF. In conclusion, the calculated GE of some feed ingredients was in agreement with the analyzed GE, which gives confidence that energy-contributing components were accounted for, but for DDGS and SBP, it was not possible to account for all analyzed GE. Concentrations of IDF and TDF, but not the physical characteristics of feed ingredients, may be used to estimate IVAID and IVATTD of DM and OM in feed ingredients.
Technische prestatie uitkomst in de stal
Jong, I.C. de; Gunnink, H. ; Hattum, T.G. van; Kempen, I. ; Baere, Kris De; Cardinaels, Sofie - \ 2018
De Pluimveehouderij 2018 (2018). - ISSN 0166-8250 - p. 57 - 59.
Vleeskuikenhouders die uitkomst in de stal als innovatief concept omarmen, geven aan dat ze positieve effecten zien op de productie, lager antibioticagebruik en minder ziektegevoeligheid. Deze veronderstelde positieve effecten ten opzichte van uitkomen in de broederij en het vervolgens transporteren van eendagskuikens is nu wetenschappelijk onderzocht.
Life histories of an invasive and native ladybird under field experimental conditions in a temperate climate
Raak-van den Berg, C.L. ; Jong, Peter W. de; Gort, Gerrit ; Manly, Bryan F.J. ; Lenteren, Joop C. van - \ 2018
Entomologia Experimentalis et Applicata 166 (2018)3. - ISSN 0013-8703 - p. 151 - 161.
Harmonia axyridis - Adalia bipunctata - Coccinellidae - Coleoptera - Competition between species - Field experimental study - Immature development - Immature survival - Intraguild predation - Life table - Northwestern Europe - Tilia × europaea
Among characteristics that are thought to determine the success of invasive species, life-history traits feature prominently. However, in most cases, these have been determined under laboratory conditions. Here, we use a field set-up to determine immature development time and survival of invasive Harmonia axyridis (Pallas) and native Adalia bipunctata L. (both Coleoptera: Coccinellidae). On caged Tilia × europaea L. cv. Pallida trees (Malvaceae) with ample amounts of aphid food, we introduced freshly hatched larvae of a single or of both ladybird species and followed their development until emergence of adults. Under the condition of ample prey availability, both ladybird species apparently hardly interacted and intraguild predation did not cause significant mortality. Development time of both species is in line with data from laboratory tests under controlled conditions. Immature survival can reach high levels, but is considerably higher for H. axyridis (44-100%) than for A. bipunctata (11-77%), resulting in faster increase of H. axyridis populations, which is one of the factors that may explain its invasion success.
Aardappeldemodag 2018: Sterke schakels verbinden
Ampt-de Jong, Marieke ; Brouwer, Thie Arend ; Mol-van de Erve, Leanne ; Tramper, Marcel - \ 2018
Serum folate and vitamin B12 are associated with body composition in elderly: The B-PROOF study
Oliai Araghi, S. ; Braun, K.V.E. ; Velde, Nathalie van der; Dijk, S. van; Schoor, Natasja M. van; Zillikens, M.C. ; Groot, C.P.G.M. de; Uitterlinden, André G. ; Stricker, B.H. ; Voortman, Trudy ; Kiefte-de Jong, J.C. - \ 2018
Kuiken kan maximaal 36 uur zonder eten
Jong, Ingrid de - \ 2018
animal welfare - animal production - poultry - animal nutrition - animal health
Effects of dietary supplementation of organic minerals, fish oil and hydrolysed collagen on growth performance and tibia characteristics of broiler chickens
Guz, Bahadir ; Molenaar, R. ; Krimpen, M.M. van; Brand, H. van den; Jong, I.C. de; Kemp, B. - \ 2018
In: Abstract of the WIAS Science Day 2018. - - p. 27 - 27.
Review of environmental enrichment for broiler chickens
Riber, A.B. ; De Weerd, H.A. Van; Jong, I.C. De; Steenfeldt, S. - \ 2018
Poultry Science 97 (2018)2. - ISSN 0032-5791 - p. 378 - 396.
behavior - broiler - environmental enrichment - production system - welfare
Welfare problems are commonly found in both conventional and organic production of broiler chickens. In order to reduce the extent of welfare problems, it has been suggested to provide stimulating, enriched environments. The aim of the present paper is to provide a review of the effect on behavior and welfare of the different kinds of environmental enrichments in the production of broilers that have been described in the scientific literature. Environmental enrichment is defined as an improvement of the environment of captive animals, which increases the behavioral opportunities of the animal and leads to improvements of the biological function. This definition has been broadened to include practical and economic aspects, as any enrichment strategy that adversely affects the health of animals or that has too many economic or practical constraints will never be implemented on commercial farms and thus never benefit animals. Environmental enrichment for broilers often has the purpose of satisfying behavioral needs and/or stimulating the broilers to an increased level of activity, which among others will reduce the occurrence of leg problems. Potentially successful environmental enrichments for broiler chickens are elevated resting-places, panels, barriers, and bales of straw ("point-source enrichment"), as well as covered verandas and outdoor ranges ("complex enriched environments"). Many of the ideas for environmental enrichment for broilers need to be further developed and studied, preferably in commercial trials, with respect to the use, the effect on behavior and on other welfare aspects such as leg health, and the interaction with genotype, production system, stocking density, light, and flock size. In addition, information on the practical application and the economics of the production system is often lacking, although it is important for application in practice.
Bovine lumpy skin disease: epidemiology, economic impact and control opportunities in Ethiopia
Abebe, Wassie Molla - \ 2018
University. Promotor(en): Mart de Jong, co-promotor(en): Klaas Frankena. - Wageningen : Wageningen University - ISBN 9789463437288 - 236

Lumpy skin disease (LSD) is a serious pox disease of cattle caused by LSD virus of the genus Capripoxvirus, subfamily Chordopoxvirinae and family Poxviridae. It is economically an important disease due to its effect on productivity, fertility, animal survival, hide quality, and trade. LSD is an endemic disease in Ethiopia having serious consequences on both national and household incomes. This PhD study has been undertaken with the main aim to generate information on LSD epidemiology, vaccination effect and financial consequences to support the formulation of a disease control strategy. An LSD outbreak occurred at least once in all of the regional states and city administrations in Ethiopia between 2000 and 2015. The average incidence of LSD outbreaks at district level was 5.58 per 16 years (0.35 per year). The trend of LSD outbreaks increased over the study period. Outbreaks were frequent at the end of the long rainy season and more numerous in areas with relatively high rain fall. The true animal level and herd level sero-prevalences were estimated as 26.5% (95% CI: 24.7-28.3) and 51.0% (95% CI: 46.8-55.1), respectively. Adult age (OR=2.44, (95% CI: 1.67-3.55)), contact with other animals (OR=0.41 (95% CI: 0.23-0.74)), and presence of water bodies (OR=1.61 (95% CI: 1.03-2.52)) were identified as the most important risk factors at individual animal level in relation to LSD sero-positivity. The transmission rate between animals in the crop-livestock production system was 0.072 (95% CI: 0.068-0.076) per day, whereas the transmission rate among animals in intensive production system was 0.076 (95% CI: 0.068-0.085) per day. The reproduction ratio (R) of LSD between animals in the crop-livestock production system was 1.07 and in the intensive production system it was 1.09. Kenyan sheep pox virus strain vaccine (KS1 O-180) significantly reduces the severity of the disease. The vaccine efficacy for susceptibility was estimated to be 0.46 (i.e. a susceptibility effect of 0.54) while the infectivity effect of the vaccine was 1.83. The LSD field outbreak economic impact assessment revealed a total economic loss of USD 1176 per affected herd (USD 489 in the subsistence and USD 2735 in the commercial farm type). The financial analysis showed a positive net profit of USD 136 per herd (USD 56 in the subsistence and USD 283 in the commercial farm type) to LSD vaccine investment. Generally, this PhD research provides insight into the epidemiology, economic impact and control opportunities of LSD in Ethiopia that can support policy makers to formulate control strategy for the disease, which is currently lacking in the country.

Concurrentie, concentratie en rentabiliteit in de glastuinbouw in Nederland
Veerman, Kees - \ 2018
University. Promotor(en): Olaf van Kooten. - Wageningen : Wageningen University - ISBN 9789463438865 - 331


The expansion of the market area of the European Union has caused a strong increase of supply and demand of fresh horticulture products of the Dutch glasshouse sector on the European market. Consequently there is increased competition with companies from new European member states, producing against lower prices, as well as changes in production and sales structure. In the Dutch food horticulture sector this led to a large horizontal and vertical merger between most of the auctions and a number of large exporters. From 1996 to 1998 VTN/The Greenery changed from a co-operative auction into a co-operative trade organisation. In the floriculture sector only horizontal mergers took place between co-operative auctions. The wholesalers/exporters remained independent. At present there are two Flower Auctions, FloraHolland te Naaldwijk (market share 98%) and Plantion in Ede (2%).

Central research question

This thesis explores the development of market structure, market strategy and market results in the horticulture glasshouse sector over the last thirty-five years. The central research question is whether the difference in market structure and market strategy in the Dutch sectors of glasshouse vegetables and glasshouse cut flowers and pot plants is a significant cause to explain the difference in market results for the growers and their co-operative organisations.

The conceptual model

A number of theories and models have been studied derived from the Industrial Organisation Theory. This theory focuses on the analysis of branches of industries, industry chains and markets involved. It examines the relation between market structure (S), market conduct (C) and market performance (P) through the SCP-model (in Dutch: SGR-model). A description and explanation is given of the static SCP-model of Bain, the dynamic SGR-model of De Jong and the branch-analysing models of Porter and Daems. The conceptual model of competition, concentration and performance (figure 1.1) has been constructed from these models to analyse the Dutch horticulture glasshouse sectors.

Research of producers, sector research and research of auctions/sales organisations

From 2006-2008 three research projects on producers were conducted amongst 40 growers of vegetables, 40 growers of cut flowers and 40 growers of pot plants, all under glass. Data and opinions of growers about their company, market strategy and performance were gathered. In the same period sector research of the development of total production, imports and exports took place in the three sectors of the glasshouse industry on sector level, on the level of sales organisations and the wholesalers/ exporters. The gathered data have been analysed and tested on selected variables. In three different chapters temporary conclusions have been drawn. The most important business and market characteristics and research outcomes are discussed in three separate tables at the end of these three chapters and the associated appendices. The research of producers was expanded in 2015/2016 on the basis of the data of the research 2006-2008 with econometric research and multiple analysis of a number of the most important variables of market structure and market conduct to explain the market results (Lerner Index).

Results of sector research

The three horticulture sectors under glass show a positive development in yearly production and export value over a period of thirty-five years, besides a small decrease in 2009 and 2011, as a result of the banking and EHEC crisis. In the Dutch floriculture sector the average growing figures are a bit higher than in the food horticulture sector because of a stronger yearly increase in the production of pot plants. In all three sectors the production and export values are increased almost every year until the banking crisis in 2009. After 2010/2011 the sectors have been recovering.

Development of variables in Dutch horticulture glasshouse sector 1980-2016

The sector cut flowers under glass show a decrease of area and production (m2 glass) in The Netherlands. However, there is an increase of import and direct supply of cut flowers from foreign growers and Dutch companies from the southern part of Africa (roses, chrysanthemums etc.). All sectors profit from the growing import/re-export function of vegetables and fruit, cut flowers and pot plants from The Netherlands to neighbouring countries and trade partners in Europe. The high share of the sector variables domestic share and export share in all three sectors stimulate the development of production value, export value and prices.

Results of research into auctions/sales organisations

In the food horticulture and floriculture sectors there has been quite a difference in market strategy and market structure since 1998. In the sector vegetables under glass the degree of concentration of the four largest sales organisations (C4) has decreased to the level of before the merger (60%). In 1997 this figure was 96%. Also the share of growers of VTN/The Greenery in the area of Dutch vegetables under glass has decreased. VTN/The Greenery did not reach her target of 1996 with their strategy of horizontal and vertical concentration: organizing a larger bundling of the turnover of the Dutch auctions and wholesalers/exporters.

The search for a good working integration of horticultural production and trade in one company with an efficient and effective structure has not been completed yet and started in 2016 with a new sales organisation. The financial position of VTN/The Greenery on the European market is not strong. Since 1996 the annual turnover has strongly fluctuated between 0.9 and 1.5 billion euros, with a variation range of 25 to 30 %. The supply of their own members halved, just like the income out of commission. The position on the Dutch market is stable, on the most important European markets difficult. The return on investment is low. In 2015 and 2016 a careful recovery started after the difficult years of crisis 2009, 2011 and 2013.

Flower auctions FloraHolland and VBA showed a clear strategy and good results around the merger of 2007. The merger was a good example of a carefully implemented strategy of horizontal concentration, bringing together the interests of the flower auctions and their members. For FloraHolland the period of the crisis 2009-2011 was a test with success.

There was an expansion of horizontal concentration across the borders: a new joint venture auction Rhein-Maas, founded together with the German organisation Landgard and there was an integration with the import auction TFA in Aalsmeer. Both organisations are important for the market position of FloraHolland. In the Dutch floriculture sector under glass there are hardly any examples of vertical concentration of producers or sales organisations with wholesalers/exporters. There are examples, though, of vertical co-operation between these organisations and international retail, especially with the larger growers of pot plants.

The auction clock, physical and digital, is the most important sales method the flower auctions use daily. For most products there is a public pricing system. It provides a transparent process of supply and demand against sharp tariffs of the auction. For cut flowers as well as for pot and garden plants a large part of the product groups are sold by way of the auction clock, which mostly ensures a reliable reference price for mediation and personal selling and provides a good match of supply and demand and a ‘clean’ market. Attention to strengthen the position of the auction clock, especially with the selling of pot and garden plants, is important. The turnover of FloraHolland decreased in 2009 (bank crisis) and increased in 2010 and 2011 just above the level of 2008. Incomes out of services dropped. As costs decreased more than incomes, profits and solvency improved in this period.

In 2012 FloraHolland realised a turnover increase of 3% compared to 2011. However, the incomes out of services decreased. In 2013 the sector performed reasonably. The turnover of FloraHolland increased slightly but costs were higher than incomes and FloraHolland had an exploitation loss. 2014 was a year of slight recovery, 2015 and 2016 ended with an increasing turnover of 3 and 4%. Profit after tax in these years are 12 and 3 million euros. For most of the growers and customers the results in 2015 and 2016 were positive. The decision of the wholesale/export (VGB) to contribute again in the promotion costs of Bloemenbureau Holland was welcomed very positively. Along with the new strategy of 2020 FloraHolland is working on the strengthening and expansion of the physical and digital market places.

Research results of producers

On producers level there is also quite a difference in market strategy, structure and results between growers in the sectors of glasshouse vegetables and glasshouse cut flowers and pot plants. At present there is a fierce struggle to survive in each sector. It seems that the small grower of cut flowers and pot plants stands a better chance than the small grower in vegetables. The most striking single relations between structure, conduct and result will be mentioned.

Most striking single relations glasshouse vegetables

- The small company has relatively higher costs than the larger types. If the sales organisation uses the principle of ‘the user pays the total costs made’ this burden is rather heavy for the smallest companies.

- Auction growers mainly deliver round or grape tomatoes, the majority of independent growers choose for the special varieties. This influences the pricing process.

- Small and large auction growers differ significantly in business size from independent growers, but realise comparable margins. Large-scale production does not always lead to lower average costs and a better margin, but it does entail a greater risk of too much supply and low prices. Growers with a larger business size are faced with larger financial problems in difficult years than smaller ones.

- Horizontal concentration of the four largest growers of vegetables lies at a low level and their sales power is low. The concentration of the four largest sales organisations is about 60%.

- Vertically integrated auction growers are smaller in business size and invest less than non- integrated independent growers. They realise comparable margins.

- The importance of the sales organisation to realise good prices and margins for the members’ products seems rather small. Sharp purchase prices are of equal importance for the trade organisation and influence the margin of the members.

- Higher investments don’t produce higher results (directly). More innovative investments are needed to improve prices and margins.

Most striking single relations glasshouse cut flowers

- The small auction grower realises an expected smaller turnover and pays higher commission than the larger auction grower, member of a growers organisation. Although there is no significant relation between grower type and realised margin, higher commission can lead to higher prices and margins. Besides the higher price level, smaller growers realise a higher solvency than larger growers.

- Growers of roses under glass realise a higher margin than growers of chrysanthemums because of a wide and deep assortment.

- Small growers of cut flowers show comparable or better results than the larger ones.

- Horizontal concentration of the four largest growers of cut flowers lies, just like the sectors of vegetables and pot plants under glass, at a low level. The small auction grower has little market power and needs the sales organisation for reasonable prices and successful sales.

- There are no significant relations between the organisation of sales and growers’ turnover, realised margin and the height of commission. It looks as if every grower uses his own mix of marketing and sales activities in a way that no significant differences in results arise.

- Selling of cut flowers by means of the auction clock gives good results.

Most striking single relations glasshouse pot plants

- The smaller auction grower, with or without personal selling, realises an expected smaller turnover but a higher margin than the larger auction grower, member of a growers organisation.

- Smaller growers (in m2 glass) get higher results or results comparable to those of the larger ones. Old and new companies get comparable margins.

- Growers of green plants get a significant lower yearly turnover than growers of blooming pot plants. Green plants are often more unique than blooming plants. That is why growers of green plants get higher prices and margins.

- Horizontal concentration of the growers of pot plants lies, just like in the other sectors, at a low level. The small auction grower has little market power and needs the sales organisation for realising reasonable prices and successful sales.

- Like in the other sectors the small grower invests less in his business than the larger ones. Higher investments do not directly produce higher results. More innovative investments are needed to improve prices and margins.

- There is a significant relation between the organisation of sales and the yearly realised turnover: larger growers use more personal selling besides the sales services of the auction, as their own business activity or as an activity of the growers organisation.

Boarding out all sales activities to FloraHolland is effective especially for the small grower and enlarges the chance of realising a higher margin. Although he pays a higher commission, he realises a higher margin because of the positive relation between commission and margin.

Producers results through econometric research

Most striking multiple relations glasshouse vegetables

The results of the econometric analysis show that in the sector glasshouse vegetables membership of a growers association produces better results on average than membership of a traditional marketing corporation. Especially young producers with new ideas about the organisation of the company and vertical co-operation with on average large and modern companies are booking the best results.

Most striking multiple relations glasshouse cut flowers

Auction growers using the auction clock exclusively to sell their products realise a higher margin on average than growers using other selling methods. The membership of a growers association produces higher results on average than no membership and smaller companies get higher margins than large ones. Senior growers get higher results than junior growers. The auction clock is the best guarantee for realising higher margins. It seems that in the sector cut flowers a larger scale has less effect on the margin than producing ‘niche’ product types. For the latter the selling method via the auction clock plays an important role. Companies with ‘niche’ products have higher fixed costs although a higher margin gives fewer problems when it comes to finance the production.

Final conclusion

The answer to the central question confirms the following: the difference in market structure and market strategy in the Dutch sectors of glasshouse vegetables and glasshouse cut flowers is a significant cause to explain the difference in market results. If we follow the position and the results of the small grower in the sector glasshouse vegetables, we are looking at a producer in a tight spot with lower average results for the grower and his co-operation in comparison with the independent grower and his grower association. In the sector glasshouse cut flowers the position and results of the small auction clock grower is better in comparison with the grower who sells on his own or via a growers association.

The results of this research indicate that in the sector glasshouse vegetables the highest margins are obtained by the independent growers associations, working either cooperativly with the classical co-operations or independent there from but in any case with their own marketing strategy. In the sector glasshouse cut flowers it is the grower selling through the auction clock who gets the highest margins. In the sector glasshouse pot plants, where the type of the product clearly differs from the perishable vegetables and cut flowers, there are too few data to draw conclusions.

Infection dynamics and effective control strategies of tuberculosis in badgers and cattle in Ireland
Aznar Asensio, J.I. - \ 2018
University. Promotor(en): Mart de Jong, co-promotor(en): Klaas Frankena. - Wageningen : Wageningen University - ISBN 9789463437264 - 161

Bovine tuberculosis (bTB) is a chronic inflammatory disease of cattle caused by infection with Mycobacterium bovis. In Ireland, a comprehensive control/eradication programme for M. bovis commenced in 1954, and by 1965, cattle incidence had been reduced by more than 95%. Despite this early and rapid success, the infection has remained relatively stable since. The inability to eradicate the disease by focusing on strategies that aimed at reducing cattle to cattle transmission suggested the presence of one or more reservoirs of the pathogen outside the cattle population. M. bovis was first isolated from a badger (Meles meles) in Ireland in 1974. Since then, a large amount of literature looking at different epidemiological aspects was dedicated to investigating the role of badgers in bTB maintenance. Evidence of the role of badgers as a disease-maintenance-host in areas of known cattle infection was gathered from the results of two large field studies carried in Ireland, the East Offaly and the four area projects. Following the proactive removal of badgers in some of the study areas, these studies demonstrated a significant reduction in cattle incidence in comparison to control areas where no badger removals were carried. In Ireland, badger culling commenced in 2000 as a short/medium term strategy to reduce the incidence of the infection in badgers, with the aim to achieve eradication in cattle. Nonetheless, there were expectations that BCG vaccination of badgers in the field, by helping to reduce M. bovis transmission in badgers and subsequently in the cattle population, would be the long term solution. In this thesis, a field trial enabling quantification of the efficacy of BCG vaccination on M. bovis transmission in badgers under field conditions was designed and analysed. Vaccine efficacy for susceptibility was estimated as VES=59% (95% CI =6.5%-82%) whereas vaccine efficacy for infectivity (VEI) was 0%, implying that there was a complete lack of effect from BCG vaccination on the infectivity of vaccinated and subsequently infected badgers. Also, the quantitative role of each of these two host species in the transmission of M. bovis within the system was assessed. Algorithms to estimate the Next Generation Matrix (NGM) and the reproduction ratio for the cattle-badger system were developed, and all plausible NGMs describing the transmission between the two species were calculated from prevalence data and the number of cattle herds and badgers, collected at the endemic steady state. Taking into account the results obtained for vaccine efficacy, and the reproduction ratios obtained, it was possible to demonstrate that for almost all these plausible transmission scenarios, BCG vaccination of badgers in addition to current controls could successfully achieve eradication of M. bovis infection in the system. Further, the small number of transmission scenarios where eradication of M. bovis from the system (by adding BCG badger vaccination to the current controls) was not feasible, were classified as highly unlikely to represent transmission in the field.

Female response to predation risk alters conspecific male behaviour during pre-copulatory mate guarding
Oku, Keiko ; Poelman, Erik H. ; Jong, Peter W. de; Dicke, Marcel - \ 2018
Ethology 124 (2018)2. - ISSN 0179-1613 - p. 122 - 130.
pre-copulatory pair - predatory mite - sex difference - solitary female - spider mite
Mating behaviour often increases predation risk, but the vulnerability within mating pairs differs between the sexes. Such a sex difference is expected to lead to differences in responses to predation risk between the sexes. In the two-spotted spider mite Tetranychus urticae, males engage in pre-copulatory mate guarding because only the first mating results in fertilisation. We investigated (i) whether pre-copulatory pairs are more conspicuous to the predatory mite Phytoseiulus persimilis than solitary females, (ii) whether the vulnerability to the predator differs between sexes within the pre-copulatory pair, (iii) whether each sex of T. urticae responds to predation risk during pre-copulatory mate guarding and (iv) whether T. urticae's response to predation risk affects predator behaviour. Because T. urticae females are immobile during pre-copulatory mate guarding, we observed male behaviour to evaluate effects of predation risk. We found that the predators detect more pre-copulatory pairs than solitary females and that more females than males of the pre-copulatory pairs are preyed upon by the predators. The preference of spider mite males for pre-copulatory pairs versus solitary females was affected by whether or not the female had been exposed to predators during development. Male T. urticae exposed to predation risk did not alter their behaviour. These results suggest that only the most vulnerable sex, that is the female, responds to predation risk, which modifies male behaviour. Regardless of T. urticae females’ experience, however, P. persimilis detected more T. urticae pre-copulatory pairs than solitary females, suggesting that pre-copulatory mate guarding itself is dangerous for T. urticae females when these predators are present. We discuss our results in the context of sex-dependent differences in predation risk.
Mercury associated neurochemical response in Arctic barnacle goslings (Branta leucopsis)
Brink, Nico W. van den; Scheiber, Isabella B.R. ; Jong, Margje E. de; Braun, Anna ; Arini, Adeline ; Basu, Niladri ; Berg, Hans van den; Komdeur, Jan ; Loonen, Maarten J.J.E. - \ 2018
Science of the Total Environment 624 (2018). - ISSN 0048-9697 - p. 1052 - 1058.
Exposure and effect - Neurotoxicity - Polar - Terrestrial - Tundra
There remains great concern over mercury pollution in the Arctic, though relatively little is known about impacts on biota that inhabit Arctic terrestrial systems. To help address this, the current study was performed with barnacle goslings (Branta leucopsis) from a coal mine-impacted site and a control site near Ny-Ålesund, Spitsbergen (Svalbard). The works focused mainly on mercury, as coal contains trace levels of this element. Total mercury concentrations were quantified in soil and vegetation from the two sites, as well as feces and liver from the goslings. Next, the mercury exposures were related to dopamine 2 (D2)- and NMDA-receptors in the brain, given that mercury is a proven neurotoxicant. Soil and vegetation in the mining area contained mercury levels that were approximately 3- and 2.2-times higher than in the control site. Despite a significant difference between the sites, the soil and vegetation mercury levels where were within ranges found at other Arctic locations. Goslings grazing in the mine-impacted area contained significantly higher hepatic mercury levels than those sampled from the control site. Compared to other species, the hepatic concentrations were relatively low possibly due to dilution of the mercury in growing goslings (growth dilution) and deposition of mercury in the growing feathers. Hepatic mercury concentrations were positively related to D2-neuroreceptor levels but not to NMDA-receptor levels thus suggesting a possible subtle neurological effect. To our knowledge, this is among the first studies on mercury exposure in Arctic terrestrial organisms, and one of the first to document potential subtle neurological responses associated with exposure to low, environmentally relevant mercury levels, which also can be found at other locations in the Arctic. However, as a pilot effort, the results here need to be examined in additional studies that include, for example, lager study designs, different geographic sites and other terrestrial species.
Fluctuations in milk yield are heritable and can be used as a resilience indicator to breed healthy cows
Elgersma, G.G. ; Jong, G. de; Linde, R. van der; Mulder, H.A. - \ 2018
Journal of Dairy Science 101 (2018)2. - ISSN 0022-0302 - p. 1240 - 1250.
Big data - Fluctuation - Health - Resilience - Variance
Automatic milking systems record an enormous amount of data on milk yield and the cow itself. These type of big data are expected to contain indicators for health and resilience of cows. In this study, the aim was to define and estimate heritabilities for traits related with fluctuations in daily milk yield and to estimate genetic correlations with existing functional traits, such as udder health, fertility, claw health, ketosis, and longevity. We used daily milk yield records from automatic milking systems of 67,025 lactations in the first parity from 498 herds in the Netherlands. We defined 3 traits related to the number of drops in milk yield using Student t-tests based on either a rolling average (drop rolling average) or a regression (drop regression) and the natural logarithm of the within-cow variance of milk yield (LnVar). Average milk yield was added to investigate the relationships between milk yield and these new traits. ASReml was used to estimate heritabilities, breeding values (EBV), and genetic correlations among these new traits and average milk yield. Approximate genetic correlations were calculated using correlations between EBV of the new traits and existing EBV for health and functional traits correcting for nonunity reliabilities using the Calo method. Partial genetic correlations controlling for persistency and average milk yield and relative contributions to reliability were calculated to investigate whether the new traits add new information to predict fertility, health, and longevity. Heritabilities were 0.08 for drop rolling average, 0.06 for drop regression, and 0.10 for LnVar. Approximate genetic correlations between the new traits and the existing health traits differed quite a bit, with the strongest correlations (-0.29 to -0.52) between LnVar and udder health, ketosis, persistency, and longevity. This study shows that fluctuations in daily milk yield are heritable and that the variance of milk production is best among the 3 fluctuations traits tested to predict udder health, ketosis, and longevity. Using the residual variance of milk production instead of the raw variance is expected to further improve the trait to breed healthy, resilient, and long-lasting dairy cows.
Quantification of Mycobacterium bovis transmission in a badger vaccine field trial
Aznar, I. ; Frankena, K. ; More, S.J. ; O'Keeffe, J. ; McGrath, G. ; Jong, M.C.M. de - \ 2018
Preventive Veterinary Medicine 149 (2018). - ISSN 0167-5877 - p. 29 - 37.
Bacille calmette-Guérin (BCG) - Badgers - Basic reproduction ratio - Mycobacterium bovis - Transmission - Vaccine efficacy for infectiousness - Vaccine efficacy for susceptibility
In the UK and Ireland, Bacille Calmette-Guérin (BCG) vaccination of badgers has been suggested as one of a number of strategies to control or even eradicate Mycobacterium bovis infection in badgers. In this manuscript, we present the results of a badger field trial conducted in Ireland and discuss how the novel trial design and analytical methods allowed the effects of vaccination on protection against infection and, more importantly, on transmission to be estimated. The trial area was divided into three zones North to South (A, B and C) where vaccination coverages of 0, 50 and 100%, respectively, were applied. Badgers were trapped over a 4 year period. Badgers were assigned to either placebo or vaccine treatment, with treatment allocation occurring randomly in zone B. Blood samples were collected at each capture, and serology was performed in these samples using a chemiluminescent multiplex ELISA system (Enfer test). The analysis aimed to compare new infections occurring in non-infected non-vaccinated badgers to those in non-infected vaccinated ones, while accounting for the zone in which the badger was trapped and the infection pressure to which this individual badger was exposed. In total, 440 records on subsequent trappings of individual non-infected badgers were available for analysis. Over the study period, 55 new infections occurred in non-vaccinated (out of 239 = 23.0%) and 40 in vaccinated (out of 201 = 19.9%) badgers. A Generalized Linear Model (GLM) with a cloglog link function was used for analysis. Statistical analysis showed that susceptibility to natural exposure with M. bovis was reduced in vaccinated compared to placebo treated badgers: vaccine efficacy for susceptibility, VES, was 59% (95% CI = 6.5%–82%). However, a complete lack of effect from BCG vaccination on the infectivity of vaccinated badgers was observed, i.e. vaccine efficacy for infectiousness (VEI) was 0%. Further, the basic reproduction ratio as a function of vaccination coverage (p) (i.e. R(p)) was estimated. Given that the prevalence of M. bovis infection in badgers in endemic areas in Ireland is approximately 18%, we estimated the reproduction ratio in the unvaccinated population as R(0) = 1.22. Because VES was now known, the reproduction ratio for a fully vaccinated population was estimated as R(1) = 0.50. These results imply that with vaccination coverage in badgers exceeding 30%, eradication of M. bovis in badgers in Ireland is feasible, provided that the current control measures also remain in place.
Small percentage of anaphylactic reactions treated with epinephrine during food challenges in Dutch children
Valk, Johanna P.M. van der; Berends, Irene ; Wijk, Roy Gerth van; Arends, Nicolette J.T. ; Maaren, Maurits S. van; Groot, Hans de; Wichers, Harry J. ; Emons, Joyce A.M. ; Dubois, Anthony E.J. ; Jong, Nicolette W. de - \ 2018
Annals of Allergy, Asthma and Immunology 120 (2018)3. - ISSN 1081-1206 - p. 300 - 303.
Background: Severe allergic reactions, including anaphylaxis, occur during oral food challenges (OFCs) and the first-line treatment of anaphylaxis is epinephrine. Objective: To evaluate the percentage of anaphylactic reactions treated with epinephrine during OFCs and to identify associated factors for the administration of epinephrine. Methods: Children who underwent an OFC with peanut, hazelnut, cow's milk, hen's egg, or cashew nut from 2005 through 2015 in the Netherlands were evaluated. Children with reactions meeting the criteria for anaphylaxis according to the European Academy of Allergy and Clinical Immunology guidelines for food allergy and anaphylaxis were included. Children with an anaphylactic reaction treated with vs without epinephrine were compared. Possible factors associated with the administration of epinephrine, such as age, sex, symptoms consistent with asthma, history of an allergic reaction to the tested allergen, and symptom types during the anaphylactic reaction, were evaluated using logistic regression analysis. Results: Eighty-three children in clinical and research settings (43% boys; median age, 7 years; range, 1-17) who met the criteria for anaphylaxis were included in this study. Thirty-two of 83 children (39%) with anaphylaxis were treated with epinephrine. Respiratory symptoms during the OFC were treated significantly more often with epinephrine than gastrointestinal symptoms (P = .01). Conclusion: Only 39% of children with anaphylaxis, according to the guideline criteria, were treated with epinephrine during the OFC and most of these children had respiratory symptoms. There is need for an easy-to-use international guideline for the treatment of allergic symptoms during OFCs.
The relationship between measures of fear of humans and lameness in broiler chicken flocks
Vasdal, G. ; Moe, R.O. ; Jong, I.C. de; Granquist, E.G. - \ 2018
Animal 12 (2018)2. - ISSN 1751-7311 - p. 334 - 339.
broiler - fear - humans - lameness - Welfare Quality
In the Welfare Quality® assessment protocol for broilers, the touch test is included to assess the human–animal relationship in the flock. The test is designed to measure the animals’ fear of humans, assuming that broilers will withdraw from the observer if they are fearful. However, many broilers close to slaughter age have impaired walking ability, and the results from the touch test may thus be biased by lameness and poor leg health. As the touch test is currently being used in several countries to assess human–animal relationship in broilers, there is an urgent need to examine this potential relationship for a further validation of the test. In the present study, fear of humans was assessed in 50 randomly selected Norwegian broiler flocks, using the touch test as described in the Welfare Quality® protocol for ty broilers. Leg health was assessed by examining the gait of 150 random birds in each of the flocks, using a six-point gait score scale from 0 to 5. The coefficient for the relationship between touch test score and gait score was 0.034 (P<0.001), indicating that the animals express less fear as assessed by the touch test when the gait scores increase. This implies that the touch test may be confounded by impaired walking ability and therefore might be a suboptimal method of assessing fear of humans and human–animal relationship in broilers. In conclusion, the results from this study suggests that the touch test must be further validated in broilers and perhaps be replaced with a fear test that doesn’t rely on walking ability.
Check title to add to marked list
<< previous | next >>

Show 20 50 100 records per page

Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.