Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Camera vervangt ervaren selecteur
    Kamp, J.A.L.M. - \ 2015
    Boerderij 100 (2015)36. - ISSN 0006-5617 - p. 50 - 53.
    akkerbouw - aardappelen - vermeerderingsmateriaal - detectie - monitoring - diagnostische technieken - fotometrie - pootaardappelen - kwaliteit - kunstmatige selectie - gewasbescherming - precisielandbouw - arable farming - potatoes - propagation materials - detection - monitoring - diagnostic techniques - photometry - seed potatoes - quality - artificial selection - plant protection - precision agriculture
    Selecteren van pootaardappelen kost de teler veel tijd en vergt een hoge mate van vakmanschap. Wellicht kan een machine dat sneller en beter. Daarom start dit jaar het vierjarige project Smart Ziekzoeken Pootaardappelen om te testen of het automatisch opsporen van zieke aardappelplanten haalbaar is. Het project wordt uitgevoerd door Praktijkonderzoek Plant en Omgeving (PPO) en specialisten van Plant Research International (beide onderdeel van Wageningen UR)
    Control of Pig Reproduction IX
    Rodriguez-Martinez, H. ; Soede, N.M. ; Flowers, W.L. - \ 2013
    Leicestershire, United Kingdom : Context Products Ltd (Society of Reproduction and Fertility volume 68) - ISBN 9781899043484 - 345
    varkens - geslachtelijke voortplanting - gameten - embryo's - kunstmatige inseminatie - embryotransplantatie - zwangerschap - partus - pasgeborenen - biggen - overleving - biotechnologie - metabolomica - eiwitexpressieanalyse - kunstmatige selectie - pigs - sexual reproduction - gametes - embryos - artificial insemination - embryo transfer - pregnancy - parturition - neonates - piglets - survival - biotechnology - metabolomics - proteomics - artificial selection
    Innovations in the dairy chain: bio-economic analysis of novel breeding opportunities
    Demeter, R.M. - \ 2011
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Alfons Oude Lansink; Miranda Meuwissen; A.R. Kristensen. - [S.l.] : S.n. - ISBN 9789461732088 - 192
    dierveredeling - melkkoeien - zuivelindustrie - kunstmatige selectie - melkproducten - genomica - melkvetpercentage - melkeiwitpercentage - animal breeding - dairy cows - dairy industry - artificial selection - milk products - genomics - milk fat percentage - milk protein percentage
    In recent years, there has been a growing interest in the dairy sector to move from producing bulk dairy commodities towards producing specialized dairy products aimed at niche markets. Dairy farmers consider shifting from commodity milk to raw milk with specialized composition to meet consumer or industrial demands. In this context, the objectives of the thesis were 1) to assess qualitatively future scenarios to create value added in the dairy chain and 2) to ex-ante assess quantitatively the technical and economic implications at farm level of producing differentiated raw milk by using genetic selection. A two-step approach was applied, where the first step assessed qualitatively the strategic opportunities offered by a wide range of novel methods emerging at various stages in the production chain, whereas the second step assessed quantitatively the implications of specific strategies on farm level. The main findings indicate that creating value added is vital for the sustainable growth of the dairy industry, and producing raw milk with specialized characteristics by using novel breeding concepts can play an important role in this process. The ex-ante quantitative assessments have found no evidence that implementing novel genetic selection strategies to change fat or protein composition in milk would have large effects on herd production and profitability. The stakeholders of the dairy industry should initiate joint action plans to capitalize on the opportunities offered by recent milk genomics research.
    Nucleotide variation and footprints of selection in the porcine and chicken genomes
    Amaral, A.J. - \ 2010
    Wageningen University. Promotor(en): Martien Groenen, co-promotor(en): Hendrik-Jan Megens; Henri Heuven. - [S.l. : S.n. - ISBN 9789085856559 - 160
    varkens - kippen - genomen - nucleotiden - genetische diversiteit - kunstmatige selectie - selectief fokken - rassen (dieren) - genetica - pigs - fowls - genomes - nucleotides - genetic diversity - artificial selection - selective breeding - breeds - genetics
    Genetics of survival in cannibalistic laying hens : the contribution of social effects
    Ellen, E.D. - \ 2009
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Piter Bijma; M.J. Wade. - [S.l. : S.n. - ISBN 9789085853664 - 168
    pluimvee - hennen - eierproductie - kannibalisme - dierveredeling - fokkerijmethoden - sociale interactie - lijnen - kunstmatige selectie - selectie - mortaliteit - overleving - pluimveehokken - diergenetica - poultry - hens - egg production - cannibalism - animal breeding - animal breeding methods - social interaction - lines - artificial selection - selection - mortality - survival - poultry housing - animal genetics
    Mortality due to cannibalism in laying hens is a worldwide economic and welfare problem occurring in all types of commercial poultry housing systems. Due to prohibition of beak-trimming and the traditional battery system in the European Union in the near future, mortality due to cannibalism in laying hens may increase. To reduce mortality in laying hens, it is possible to use genetic selection. Mortality due to cannibalism, however, depends on social interactions between group members. Traditional selection methods neglect these social interactions, meaning that they ignore the genetic effect an individual has on its group members. These methods are, therefore, not very effective. The main aim of this thesis is to investigate the effect of social interactions on the heritable variance in mortality due to cannibalism in laying hens and to develop a selection method that takes into account social interactions.
    To investigate the effect of social interactions on the heritable variance in mortality due to cannibalism, genetic parameters for direct and associative effects on survival time in three layer lines were estimated. For all three layer lines it was found that social interactions contribute approximately two-third of the heritable variation in survival time. The heritable variation in survival time is, therefore, substantially larger than suggested by the traditional methods currently used in poultry breeding.
    To improve traits affected by social interactions in laying hens, a solution is to select individually housed candidates based on the performance of their full sibs kept in family groups. Theoretical results suggest that this selection method offers good opportunities to improve traits affected by social interactions. A selection experiment was applied aiming to improve mortality due to cannibalism in laying hens using selection based on relatives. After one generation, mortality was 10% lower in the selection line compared to the control. In the second generation, no significant effect was found, which seemed to be related to environmental factors.
    Results in this thesis suggest that prospects for reducing mortality due to cannibalism by means of genetic selection are good. Using selection methods that incorporate social interactions may lead to substantial reduction of one of the major welfare problems in egg production. Further research is needed to investigate the effect of group size and kin recognition on social interactions.

    Cold stress and immunity: Do chickens adapt to cold by trading-off immunity for thermoregulation?
    Hangalapura, B.N. - \ 2006
    Wageningen University. Promotor(en): Bas Kemp, co-promotor(en): Henk Parmentier; Henry van den Brand. - s.n. : S.n. - ISBN 9789085043584 - 160
    kippen - koudestress - voedselbeperking - immuniteit - immuniteitsreactie - kunstmatige selectie - genetica - adaptatie - diergezondheid - fowls - cold stress - food restriction - immunity - immune response - artificial selection - genetics - adaptation - animal health
    Future animal husbandry aims at enhanced animal welfare, with minimal use of preventive medical treatments. These husbandry conditions will resemble more natural or ecological conditions. Under such farming systems, animals will experience various kinds of stressors such as environmental (e.g. cold, heat, wind), and social stressors (e.g. pecking in chicken, competition for food). In Western Europe, environmental temperature can drop significantly below the optimal temperature needed for poultry farming during winter season. Apart from cold stress, competition for food could pose nutritional stress in future husbandry practices. Therefore, cold and nutritional stressors can pose a significant threat for poultry farming, as stressors are believed to affect health and welfare of animals. However, effects of cold and nutritional stress on health of poultry are not clearly understood. It has also been proposed that "artificial selection for a trait (e.g. growth, egg production) may program an individual to allocate a large portion of its resources to a demand, leaving it lacking the ability to respond to other demands". Therefore, the focus of this thesis was a) to understand the effects of cold and nutritional stressors on health status (immunocompetence) of two lines of chicken which have selectively been bred for high and low health status (antibody responses). b) to understand the effects of artificially selection on adaptive capacity of chickens to stressful conditions. Important findings of the present thesis are 1. both cold and nutritional stressors did not affect specific antibody responses. 2. both cold and moderate nutritional stressors have positive effect on innate immune component (e.g. phagocytic activity, natural antibody levels), both at cellular and gene levels. 3. cold stress suppresses plasma corticosterone levels in a dose dependent manner, whereas severe nutritional stress enhances plasma corticosterone levels. 4. inverse relation was found between cell mediate immune competence and plasma corticosterone levels. 5. genetic selection for a trait (e.g. selection for either high or low antibody levels) did not affect the immunological adaptive capacity of chickens to both cold and nutritional stressors. It was concluded that cold and nutritional stressors may not pose significant threat for the health of chickens in future farming conditions.
    Selection for longevity in dairy cattle
    Vollema, A.R. - \ 1998
    Agricultural University. Promotor(en): E.W. Brascamp; A.F. Groen. - S.l. : Vollema - ISBN 9789054858782 - 155
    melkvee - selectief fokken - kunstmatige selectie - fokwaarde - gebruiksduur - productieve levensduur - kenmerken - heritability - dairy cattle - selective breeding - artificial selection - breeding value - longevity - productive life - traits - heritability

    This thesis deals with several aspects of longevity of dairy cattle. When breeding organizations want to implement longevity in their breeding programs they have to make several decisions. This thesis aims to give tools to make those decisions.

    Chapter 2 gives an overview of the literature containing estimates of heritabilities of longevity traits and correlations between longevity and conformation traits. The results of Chapters 3 and 4 of this thesis are included as well. There are many different definitions of longevity. In this thesis, two distinctions are made: 1. between lifetime and stayability traits, and 2. between uncorrected and functional longevity traits. Lifetime traits measure the period a cow is alive or producing, and are usually expressed in days. Stayability traits measure whether or not a cow is alive at a certain point in time. Functional longevity traits are corrected for milk production, thus aiming to be a better measure for involuntary culling. In Chapters 1 and 7 of this thesis, residual longevity is introduced, which is longevity corrected not only for milk production but also for all other traits that are already in the breeding goal. So far, this trait has not been used in practice. From the literature it is concluded that, in general, heritability of longevity traits is below 0.10. The heritability of stayability traits is lower (around 0.04) than that of lifetime traits (around 0.09), and the heritability of functional longevity traits is lower (around 0.07 for lifetime traits and around 0.03 for stayability traits) than that of uncorrected longevity traits. Genetic correlations among different longevity traits are generally strong. Genetic correlations between longevity and conformation traits are strongest for conformation traits describing the mammary system and, to a lesser extent, feet and legs. The reliability of a breeding value prediction of a sire based solely on the conformation information of his daughters is approximately 55% at maximum.

    In Chapter 3, the longevity realized of cows born in different years (1978 through 1985) has been calculated. Longevity of cows born in 1978 through 1984 decreases, and longevity of cows born in 1985 is at the same level as the longevity of cows born in 1978. In 1984, the quota system was implemented in the Netherlands and farmers culled 20% more cows than their normal annual culling percentage. These cows, of course, were born before 1984. Besides this process, during the eighties large-scale crossing with Holstein-Friesian bulls took place. The original Dutch-Friesian cow population was replaced by Holstein-Friesians, and this process was accelerated by imlementation of the quota system. Both processes not only affected longevity of dairy cows realized in the Netherlands, but also the estimates of heritabilities. Data on cows born in 1978, 1982, or 1985 were used to estimate heritabilities, and the estimates were highest for the 1978 dataset, lower for the 1982 dataset, and lowest for the 1985 dataset. Possible explanations are that the population was under strong selection during the period considered, that the genetic background of the population changed, and that under the quota system, farmers base their culling decisions on a shorter planning horizon, thus increasing the environmental variation of longevity traits.

    In Chapter 4, data on cows born in different years (1978, 1982, and 1989/1990) were used to estimate genetic correlations between longevity and conformation traits. These parameters were also affected by the changing population structure during the eighties. In the 1978 data file, the correlation between functional herdlife and type was rather weak (0.16) while in the 1982 data file, this correlation was very strong (0.46). For the 1989/1990 data file, only stayability traits could be analysed because cows had not had enough time to be culled. The correlation between functional stayability until 48 months of age and type was 0.21. The strongest correlation was between functional stayability and the subjective score for udder (0.93), followed by the subjective score for feet and legs (0.43). The estimate of 0.93 is probably too high but also from other studies it was concluded that, apart from production, the udder is the most important factor determining longevity of a dairy cow. From Chapters 3 and 4 it was concluded that especially in an upgrading population estimates of genetic parameters should be based on the most recent data possible, and that estimation of these parameters should be repeated regularly.

    In Chapter 5 the value of a relatively new method in animal breeding was investigated: survival analysis. Survival analysis differs in two aspects from traditional methods of analysis: 1. it correctly utilizes information from censored records, i.e., records of cows that are still alive at the moment of data collection; and 2. effects can be modelled in a time-dependent way, yielding a more realistic model. Breeding values of sires for longevity were estimated in three different ways: as the average realized longevity of the sire's daughters, with a best linear unbiased prediction, and with survival analysis. This was done using data from small and from large farms to identify a possible genotype by environment interaction. The phenotypic average of the sire's daughters had weak rank correlations with the other two methods of breeding value prediction (ranging from -0.32 to 0.46). The correlation between the best linear unbiased prediction and the survival analysis prediction was strong (-0.91 and -0.94 on small and large farms, respectively) if only uncensored records were used in the survival analysis, and weaker (-0.71 on both small and large farms) if censored records were included as well. Correlations were negative due to the definition of the traits: in the best linear unbiased prediction the length of productive life was analysed, and in the survival analysis the risk of being culled. A long length of productive life is associated with a small risk of being culled. Thus it was concluded that best linear unbiased prediction and survival analysis mainly differ by the data that can be included in the analysis. No different rankings of sires on small or large farms were found with any of the three methods. From the survival analysis, it appeared that cows with a high percentage of Holstein-Friesian genes had a lower chance of being culled than cows with a low percentage, confirming the hypothesis in Chapters 3 and 4.

    Even though censored records can be analysed as well in survival analysis, a certain number of uncensored data is needed for a reliable breeding value prediction. Young bulls will probably not have a sufficient large number of daughters that have already been culled. Thus, conformation traits might be used for an early breeding value prediction, because they have reasonably strong correlations with longevity and can be measured early in a cow's life. In practice, a breeding value prediction will contain parental information on longevity, direct information on longevity of a sire's daughters, and indirect information on conformation of a sire's daughters. In Chapter 6 survival analysis was used to investigate the importance of conformation traits for the risk of a cow to be culled. This risk was corrected for milk production. Both the phenotypes of the cows themselves and their sires' breeding values for conformation were included in a model. The cows' phenotypes explained more variation in the risk of being culled than their sires' breeding values. In general, smaller cows with a steep rump angle, shallow udder, high score for udder and for feet and legs had the lowest chance of being culled. Survival analysis was also used to predict breeding values of sires for longevity based solely on the longevity of their daughters. These breeding values were correlated with the sires' national proofs for conformation traits, to obtain approximations of genetic correlations. The correlations were strong for nearly all conformation traits except height, rear legs set, and size. In the national proofs the conformation traits were not corrected for each other, while in the survival analysis they were.

    In Chapter 7 it was argued that survival analysis should be used whenever possible to predict breeding values for longevity, even though with current computer capacities only a sire model can be used. Choosing this method implies that a lifetime trait has to be analysed. If length of productive life is analysed, a Weibull model can be assumed, which simplifies the calculations. In practice, this breeding value prediction will have to be combined with information on conformation to obtain a reliable breeding value for longevity early in a bull's life. Because most breeding programs of dairy cows pay already much attention to milk production, functional longevity will be more informative for breeding decisions than uncorrected longevity.

    Wolda, H. ; Centrum voor Landbouwpublikaties en Landbouwdocumentatie (PUDOC), - \ 1975
    Wageningen : Pudoc (Biologische Raad reeks ) - 240
    diergedrag - kunstmatige selectie - ecologie - evolutie - gewoonten - natuurlijke selectie - plantenecologie - populatie-ecologie - populatiebiologie - animal behaviour - artificial selection - ecology - evolution - habits - natural selection - plant ecology - population ecology - population biology
    Biologische Raad KNAW
    Populatiebiologie : voordrachten tijdens het symposium georganiseerd door de Biologische raad van de Koninklijke Nederlandse akademie van wetenschappen te Amsterdam op 31 maart en 1 april 1967
    Wolda, H. ; Centrum voor Landbouwpublikaties en Landbouwdocumentatie (PUDOC), - \ 1967
    Wageningen : Pudoc (Biologische Raad reeks ) - 240
    ecologie - diergedrag - gewoonten - plantenecologie - populatie-ecologie - natuurlijke selectie - kunstmatige selectie - evolutie - populatiebiologie - ecology - animal behaviour - habits - plant ecology - population ecology - natural selection - artificial selection - evolution - population biology
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