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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    Genetic diversity and phenotypic variation of wild, feral and cultivated Coffea canephora in relation to drought stress
    Kiwuka, Catherine - \ 2020
    Wageningen University. Promotor(en): N.P.R. Anten, co-promotor(en): J. Vos; V. Poncet. - Wageningen : Wageningen University - ISBN 9789463955379 - 180
    Development and evaluation of a genome-wide Coffee 8.5K SNP array and its application for high-density genetic mapping and for investigating the origin of Coffea arabica L.
    Merot-L'anthoene, Virginie ; Tournebize, Rémi ; Darracq, Olivier ; Rattina, Vimel ; Lepelley, Maud ; Bellanger, Laurence ; Tranchant-Dubreuil, Christine ; Coulée, Manon ; Pégard, Marie ; Metairon, Sylviane ; Fournier, Coralie ; Stoffelen, Piet ; Janssens, Steven B. ; Kiwuka, Catherine ; Musoli, Pascal ; Sumirat, Ucu ; Legnaté, Hyacinthe ; Kambale, Jean Léon ; Ferreira da Costa Neto, João ; Revel, Clara ; Kochko, Alexandre de; Descombes, Patrick ; Crouzillat, Dominique ; Poncet, Valérie - \ 2019
    Plant Biotechnology Journal 17 (2019)7. - ISSN 1467-7644 - p. 1418 - 1430.
    C. canephora - C. eugenioides - Coffea arabica origin - genetic map - single-nucleotide polymorphism - SNP array

    Coffee species such as Coffea canephora P. (Robusta) and C. arabica L. (Arabica) are important cash crops in tropical regions around the world. C. arabica is an allotetraploid (2n = 4x = 44) originating from a hybridization event of the two diploid species C. canephora and C. eugenioides (2n = 2x = 22). Interestingly, these progenitor species harbour a greater level of genetic variability and are an important source of genes to broaden the narrow Arabica genetic base. Here, we describe the development, evaluation and use of a single-nucleotide polymorphism (SNP) array for coffee trees. A total of 8580 unique and informative SNPs were selected from C. canephora and C. arabica sequencing data, with 40% of the SNP located in annotated genes. In particular, this array contains 227 markers associated to 149 genes and traits of agronomic importance. Among these, 7065 SNPs (~82.3%) were scorable and evenly distributed over the genome with a mean distance of 54.4 Kb between markers. With this array, we improved the Robusta high-density genetic map by adding 1307 SNP markers, whereas 945 SNPs were found segregating in the Arabica mapping progeny. A panel of C. canephora accessions was successfully discriminated and over 70% of the SNP markers were transferable across the three species. Furthermore, the canephora-derived subgenome of C. arabica was shown to be more closely related to C. canephora accessions from northern Uganda than to other current populations. These validated SNP markers and high-density genetic maps will be useful to molecular genetics and for innovative approaches in coffee breeding.

    In search of artificial domatia for predatory mites
    Bresch, C. ; Carlesso, L. ; Suay, R. ; Oudenhove, L. van; Touzeau, S. ; Fatnassi, H. ; Ottenwaelder, L. ; Paris, B. ; Poncet, C. ; Mailleret, L. ; Messelink, G.J. ; Parolin, P. - \ 2019
    Biocontrol Science and Technology 29 (2019). - ISSN 0958-3157 - p. 131 - 148.
    banker plant - biological pest control - domatia - microhabitat - Neoseiulus californicus - Tetranychus urticae

    Banker plants can enhance biological pest control by providing both floral resources and appropriate oviposition sites, e.g. through acarodomatia, to predator species. The use of materials mimicking domatia i.e. artificial domatia may be an economically favourable alternative to the use of banker plants bearing domatia. The aim of the present study was to identify materials that are able to host eggs of the Neoseiulus californicus predatory mite but not those of the Tetranychus urticae pest mite. In a laboratory experiment, the oviposition of predatory and phytophagous mites were compared in Petri dishes containing leaves. The different modalities compared were (i) natural domatia of Viburnum tinus or (ii) one of twelve potential artificial domatia materials. The overall oviposition response of predatory mites to all artificial domatia was similar to that of the natural domatia. The oviposition of the Tetranychus urticae pest mite did not increase in response to the artificial domatia. Five artificial domatia hosted as many eggs of the predatory mite as observed in the natural domatia. The effect of the physical properties of artificial domatia was also tested and N. californicus was found to favour the artificial domatia that had high heat retention capacities for oviposition. Three of these artificial domatia were tested on rose plants in a greenhouse experiment; none of which enhanced the biological control on the plants under these conditions. The present study highlights the difficulty in identifying and using suitable artificial domatia as substitutes to banker plants in biological pest control efforts.

    Genome-wide association mapping of flowering and ripening periods in apple
    Urrestarazu, Jorge ; Muranty, Hélène ; Denancé, Caroline ; Leforestier, Diane ; Ravon, Elisa ; Guyader, Arnaud ; Guisnel, Rémi ; Feugey, Laurence ; Aubourg, Sébastien ; Celton, Jean Marc ; Daccord, Nicolas ; Dondini, Luca ; Gregori, Roberto ; Lateur, Marc ; Houben, Patrick ; Ordidge, Matthew ; Paprstein, Frantisek ; Sedlak, Jiri ; Nybom, Hilde ; Garkava-Gustavsson, Larisa ; Troggio, Michela ; Bianco, Luca ; Velasco, Riccardo ; Poncet, Charles ; Théron, Anthony ; Moriya, Shigeki ; Bink, Marco C.A.M. ; Laurens, François ; Tartarini, Stefano ; Durel, Charles Eric - \ 2017
    Frontiers in Plant Science 8 (2017). - ISSN 1664-462X
    Adaptive traits - Association genetics - Germplasm collection - GWAS - Malus × domestica Borkh - Microsynteny - Quantitative trait loci - SNP
    Deciphering the genetic control of flowering and ripening periods in apple is essential for breeding cultivars adapted to their growing environments. We implemented a large Genome-Wide Association Study (GWAS) at the European level using an association panel of 1,168 different apple genotypes distributed over six locations and phenotyped for these phenological traits. The panel was genotyped at a high-density of SNPs using the Axiom®Apple 480 K SNP array. We ran GWAS with a multi-locus mixed model (MLMM), which handles the putatively confounding effect of significant SNPs elsewhere on the genome. Genomic regions were further investigated to reveal candidate genes responsible for the phenotypic variation. At the whole population level, GWAS retained two SNPs as cofactors on chromosome 9 for flowering period, and six for ripening period (four on chromosome 3, one on chromosome 10 and one on chromosome 16) which, together accounted for 8.9 and 17.2% of the phenotypic variance, respectively. For both traits, SNPs in weak linkage disequilibrium were detected nearby, thus suggesting the existence of allelic heterogeneity. The geographic origins and relationships of apple cultivars accounted for large parts of the phenotypic variation. Variation in genotypic frequency of the SNPs associated with the two traits was connected to the geographic origin of the genotypes (grouped as North+East, West and South Europe), and indicated differential selection in different growing environments. Genes encoding transcription factors containing either NAC or MADS domains were identified as major candidates within the small confidence intervals computed for the associated genomic regions. A strong microsynteny between apple and peach was revealed in all the four confidence interval regions. This study shows how association genetics can unravel the genetic control of important horticultural traits in apple, as well as reduce the confidence intervals of the associated regions identified by linkage mapping approaches. Our findings can be used for the improvement of apple through marker-assisted breeding strategies that take advantage of the accumulating additive effects of the identified SNPs.
    Genome wide association study of two phenology traits (flowering time and maturity date) in apple
    Muranty, Hélène ; Urrestarazu, J. ; Denancé, C. ; Leforestier, D. ; Ravon, E. ; Guyader, A. ; Guisnel, R. ; Feugey, L. ; Tartarini, S. ; Dondini, L. ; Gregori, R. ; Lateur, M. ; Houben, E.H.P. ; Sedlak, J. ; Paprstein, F. ; Ordidge, M. ; Nybom, H. ; Garkava-Gustavsson, L. ; Troggio, M. ; Bianco, L. ; Velasco, R. ; Poncet, C. ; Théron, Anthony ; Bink, M.C.A.M. ; Laurens, F. ; Durel, C.E. - \ 2017
    In: 14th EUCARPIA Symposium on Fruit Breeding and Genetics International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462611689 - p. 411 - 417.
    Germplasm collections - Malus × domestica - Marker-assisted selection
    The aim of Genome Wide Association Studies (GWAS) is to identify markers in tight linkage disequilibrium with loci controlling quantitative trait variation. These markers can then be used in marker-assisted selection (MAS) in fruit crops such as apple. The GWAS approach involves both phenotyping of a large population of mostly unrelated individuals for the traits of interest, and genotyping at high marker density. In the EU-FP7 project FruitBreedomics, almost 1,200 European diploid dessert apple accessions (old and/or local cultivars) from six germplasm collections were genotyped with the Affymetrix Axiom-Apple480K array (487,000 SNPs). Phenotypic data on a large number of traits have been gathered during the project. Here we focus on flowering period and harvesting date. Knowledge of the genetic control of these traits is necessary to develop cultivars that can face the challenges imposed by global climate change and to target cultivar development as a function of a prolonged vegetation period in the production regions. Different models were tested, including control for effects of population structure and relatedness between cultivars. The full model, controlling for both structure and relatedness, was shown to be the most appropriate to avoid spurious marker-trait associations. When analyzing data over all collections, one significant marker-trait association was obtained for each trait, on chromosomes 9 and 3, for flowering period and harvesting date, respectively. Thereby, genomic locations previously identified in bi-parental populations could now be confirmed for a genetically diverse germplasm.
    TanDEM-X elevation model data for canopy height and aboveground biomass retrieval in a tropical peat swamp forest
    Schlund, Michael ; Poncet, Felicitas von; Kuntz, Steffen ; Boehm, Hans Dieter Viktor ; Hoekman, Dirk H. ; Schmullius, Christiane - \ 2016
    International Journal of Remote Sensing 37 (2016)21. - ISSN 0143-1161 - p. 5021 - 5044.

    It was demonstrated in the past that radar data is useful to estimate aboveground biomass due to their interferometric capability. Therefore, the potential of a globally available TanDEM-X digital elevation model (DEM) was investigated for aboveground biomass estimation via canopy height models (CHMs) in a tropical peat swamp forest. However, CHMs based on X-band interferometers usually require external terrain models. High accurate terrain models are not available on global scale. Therefore, an approach exclusively based on TanDEM-X and the decrease of accuracy compared to an approach utilizing a high accurate terrain model is assessed. In addition, the potential of X-band interferometric heights in tropical forests needs to be evaluated. Therefore, two CHMs were derived from an intermediate TanDEM-X DEM (iDEM; as a precursor for WorldDEMTM) alone and in combination with lidar measurements used as terrain model. The analysis showed high accuracies (root mean square error [RMSE] = 5 m) for CHMs based on iDEM and reliable estimation of aboveground biomass. The iDEM CHM, exclusively based on TanDEM-X, achieved a poor R2 of 0.2, nonetheless resulted in a cross-validated RMSE of 54 t ha−1 (16%). The low R2 suggested that the X-band height alone was not sufficient to estimate an accurate CHM, and thus the need for external terrain models was confirmed. A CHM retrieved from the difference of iDEM and an accurate lidar terrain model achieved a considerably higher correlation with aboveground biomass (R2 = 0.68) and low cross-validated RMSE of 24.5 t ha−1 (7.5%). This was higher or comparable to other aboveground biomass estimations in tropical peat swamp forests. The potential of X-band interferometric heights for CHM and biomass estimation was thus confirmed in tropical forest in addition to existing knowledge in boreal forests.

    Development and validation of the Axiom®Apple480K SNP genotyping array
    Bianco, Luca ; Cestaro, Alessandro ; Linsmith, Gareth ; Muranty, Hélène ; Denancé, Caroline ; Théron, Anthony ; Poncet, Charles ; Micheletti, Diego ; Kerschbamer, Emanuela ; Pierro, Erica A. Di; Larger, Simone ; Pindo, Massimo ; De Weg, Eric Van; Davassi, Alessandro ; Laurens, François ; Velasco, Riccardo ; Durel, Charles Eric ; Troggio, Michela - \ 2016
    The Plant Journal 86 (2016)1. - ISSN 0960-7412 - p. 62 - 74.
    genome-wide association study - genotyping - linkage mapping - Malus × domestica Borkh. - SNP chip - validation

    Cultivated apple (Malus × domestica Borkh.) is one of the most important fruit crops in temperate regions, and has great economic and cultural value. The apple genome is highly heterozygous and has undergone a recent duplication which, combined with a rapid linkage disequilibrium decay, makes it difficult to perform genome-wide association (GWA) studies. Single nucleotide polymorphism arrays offer highly multiplexed assays at a relatively low cost per data point and can be a valid tool for the identification of the markers associated with traits of interest. Here, we describe the development and validation of a 487K SNP Affymetrix Axiom® genotyping array for apple and discuss its potential applications. The array has been built from the high-depth resequencing of 63 different cultivars covering most of the genetic diversity in cultivated apple. The SNPs were chosen by applying a focal points approach to enrich genic regions, but also to reach a uniform coverage of non-genic regions. A total of 1324 apple accessions, including the 92 progenies of two mapping populations, have been genotyped with the Axiom®Apple480K to assess the effectiveness of the array. A large majority of SNPs (359 994 or 74%) fell in the stringent class of poly high resolution polymorphisms. We also devised a filtering procedure to identify a subset of 275K very robust markers that can be safely used for germplasm surveys in apple. The Axiom®Apple480K has now been commercially released both for public and proprietary use and will likely be a reference tool for GWA studies in apple.

    Classification of urban structural types with multisource data and structured models
    Montanges, Arnaud Poncet ; Moser, Gabriele ; Taubenböck, Hannes ; Wurm, Michael ; Tuia, Devis - \ 2015
    In: 2015 Joint Urban Remote Sensing Event, JURSE 2015. - Institute of Electrical and Electronics Engineers Inc. (2015 Joint Urban Remote Sensing Event, JURSE 2015 ) - ISBN 9781479966523

    In this paper, we study the land use distribution of the city of Munich, Germany. We describe the city as a set of Urban Structural Types (UST) related to the type of spatial patterns occurring within regions composed of 200m side cells. To do so, we resort to a set of multimodal descriptors extracted from remote sensing data, a 3D city model and open access vector information. Based on these descriptors, we train a SVM classifier and apply two structured prediction models to enforce spatial relationships (Markov and Conditional Random fields).

    TanDEM-X data for aboveground biomass retrieval in a tropical peat swamp forest
    Schlund, Michael ; Poncet, Felicitas von; Kuntz, Steffen ; Schmullius, Christiane ; Hoekman, D.H. - \ 2015
    Remote Sensing of Environment 158 (2015). - ISSN 0034-4257 - p. 255 - 266.
    Biomass - Interferometric coherence - REDD+ - TanDEM-X - Tropical forests

    Forests play an important role in the global carbon cycle as a carbon sink. Deforestation and degradation of forests lead to carbon emissions, which should be prevented or minimized by protecting forests. Radar remote sensing has proven to be particularly useful to monitor forests especially in the tropics due to weather and daytime independence. Radar data from the TanDEM-X mission provide a potential opportunity to monitor large areas of tropical forests due to the multi-temporal global coverage and the high resolution. Tropical peat swamp forests are difficult to access and thus high effort to conduct field measurements is necessary. Therefore, aboveground biomass was estimated from a limited amount of in-situ measurements of relatively undisturbed peat swamp forest and a LiDAR based canopy height model to achieve a representative amount of biomass estimates for radar analysis. The LiDAR and field measurements resulted in an identical estimate of mean biomass and thus provided a reliable source to correlate with SAR (synthetic aperture radar) features from the TanDEM-X mission and ultimately up-scale the found relation to the entire study site. The relationship of interferometric coherence of the bistatic TanDEM-X data showed a moderate to high correlation with the biomass (R2=0.5) and RMSE of 53t/ha corresponding to a biomass range from 183 to 495t/ha. Thus, it could be used to indicate forest degradation areas, which are characterized by larger opening of the canopy cover and thus lower biomass. The results indicate that interferometric coherence is useful for quantification of aboveground biomass in tropical peat swamp forest. TanDEM-X coherence can at minimum serve as a stratification to assess spatial distribution of qualitative biomass classes in the context of REDD+ monitoring, reporting, and verification schemes and for the identification of forest degradation areas.

    Importance of bistatic SAR features from TanDEM-X for forest mapping and monitoring
    Schlund, M. ; Poncet, F. von; Hoekman, D.H. ; Kuntz, S. ; Schmullius, C. - \ 2014
    Remote Sensing of Environment 151 (2014)sp. issue. - ISSN 0034-4257 - p. 16 - 26.
    land-cover - southeast-asia - feature-selection - polarimetric sar - tropical-forest - decision tree - alos palsar - rain-forest - sir-c - classification
    Deforestation and forest degradation are one of the important sources for human induced carbon dioxide emissions and their rates are highest in tropical forests. For man-kind, it is of great importance to track land-use conversions like deforestation, e.g. for sustainable forest management and land use planning, for carbon balancing and to support the implementation of international initiatives like REDD + (Reducing Emissions from Deforestation and Degradation). SAR (synthetic aperture radar) sensors are suitable to reliably and frequently monitor tropical forests due to their weather independence. The TanDEM-X mission (which is mainly aimed to create a unique global high resolution digital elevation model) currently operates two X-band SAR satellites, acquiring interferometric SAR data for the Earth's entire land surface multiple times. The operational mission provides interferometric data as well as mono- and bistatic scattering coefficients. These datasets are homogenous, globally consistent and are acquired in high spatial resolution. Hence, they may offer a unique basic dataset which could be useful in land cover monitoring. Based on first datasets available from the TanDEM-X mission, the main goal of this research is to investigate the information content of TanDEM-X data for mapping forests and other land cover classes in a tropical peatland area. More specifically, the study explores the utility of bistatic features for distinguishing between open and closed forest canopies, which is of relevance in the context of deforestation and forest degradation monitoring. To assess the predominant information content of TanDEM-X data, the importance of information derived from the bistatic system is compared against the monostatic case, usually available from SAR systems. The usefulness of the TanDEM-X mission data, i.e. scattering coefficients, derived textural information and interferometric coherence is investigated via a feature selection process. The resulting optimal feature sets representing a monostatic and a bistatic SAR dataset were used in a subsequent classification to assess the added value of the bistatic TanDEM-X features in the separability of land cover classes. The results obtained indicated that especially the interferometric coherence significantly improved the separability of thematic classes compared to a dataset of monostatic acquisition. The bistatic coherence was mainly governed by volume decorrelation of forest canopy constituents and carries information about the canopy structure which is related to canopy cover. In contrast, the bistatic scattering coefficient had no significant contribution to class separability. The classification with coherence and textural information outperformed the classification with the monostatic scattering coefficient and texture by more than 10% and achieved an overall accuracy of 85%. These results indicate that TanDEM-X can serve as a valuable and consistent source for mapping and monitoring tropical forests.
    Relationship of Canopy Cover with TanDEM-X Features in a Tropical Peat Swamp Forest
    Schlund, M. ; Poncet, F. von; Kuntz, S. ; Hoekman, D.H. - \ 2013
    In: GI_Forum 2013 Creating the GISociety - Conference Proceedings. - Berlin : Wichmann Verlag - ISBN 9783879075324 - p. 109 - 112.
    Monitoring of tropical forests and peat swamp forests becomes increasingly important in order to reduce carbon emissions from deforestation and forest degradation. SAR systems are suitable for that purpose due to their weather independence and sensitivity for changes in time series. The TanDEM-X mission delivers global datasets of a single-pass SAR interferometer, which provides more information in comparison to normal X-band SAR acquisitions. In particular the interferometric coherence can be regarded as useful information because it is dependent on tree height and canopy cover representing stand structure, which are important parameters for monitoring of forests.
    Recent developments and market opportunities for IPM in greenhouse tomatoes in southern Europe; Consequences for advanced IPM toolboxes and greenhouse engineering
    Velden, N.J.A. van der; Suay, R. ; Urbaneja, A. ; Giorgini, M. ; Ruocco, M. ; Poncet, C. ; Lefèvre, A. - \ 2012
    The Hague : LEI, part of Wageningen UR (LEI memorandum / LEI Wageningen UR 12-077) - 41
    marktonderzoek - geïntegreerde bestrijding - tomaten - pesticidenresiduen - glastuinbouw - zuid-europa - duitsland - market research - integrated control - tomatoes - pesticide residues - greenhouse horticulture - southern europe - germany
    The market for greenhouse tomatoes requires a production system with lower use and risks of pesticides. These requirements culminate in the tight restrictions on residues for German retailers, both in number and in levels of residues. Germany is an important import country for tomatoes because of the size of the German market. Furthermore, exports to Germany entail a price premium. For that reason the revenues of IPM in greenhouse tomatoes are more important than the costs. Consequently, the experiments in task 3 and the ex post assessment in task 4 of work package 7 of the Pure programme should focus on IPM strat egies by which the German residue restrictions can be respected.
    Distribution and abundance of the Southern Fulmar Fulmarus glacialoides
    Creuwels, J.C.S. ; Poncet, S. ; Hodum, P.J. ; Franeker, J.A. van - \ 2007
    Polar Biology 30 (2007)9. - ISSN 0722-4060 - p. 1083 - 1097.
    antarctic seabirds - prydz bay - breeding seabirds - windmill islands - petrels - adelie - birds - populations - albatrosses - fisheries
    We reviewed published and unpublished literature to establish the status of the breeding distribution and abundance of Southern Fulmars Fulmarus glacialoides. The species breeds widely throughout the Antarctic and on peri-Antarctic islands. From breeding population data collated from 73 of these localities, we estimated the minimum global population to be about 400,000 breeding pairs. After adjusting for seasonal variation in numbers of breeding pairs based on studies at Ardery Island, East Antarctica, the total global population is estimated to be at least one million breeding pairs. Of this, 72% nest on islands of the Scotia Sea arc and the South Atlantic Ocean. The precision of the estimate on the total number of breeding pairs is low, as several colony estimates were only available as orders of magnitude. Furthermore, different timing of the surveys and the difficulties of censusing colonial cliff-nesting birds reduced the count accuracy. Currently, there are no known threats to the global population, although the effects of fishery activities are not fully known.
    Rumen escape nitrogen from forages in sheep: comparison of in situ and in vitro techniques using in vivo data
    Gosselink, J.M.J. ; Dulphy, J.P. ; Poncet, C. ; Aufrère, J. ; Tamminga, S. ; Cone, J.W. - \ 2004
    Animal Feed Science and Technology 116 (2004)1-2. - ISSN 0377-8401 - p. 35 - 51.
    purine derivative excretion - protein-degradation - dry-matter - chemical-composition - perennial ryegrass - net carbohydrate - crude protein - feed-intake - digestion - cattle
    The objective of this study was to relate in vivo data of rumen escape N (REN) of forages with REN estimated from models and with determinations of rumen undegradable N. For these determinations and models measurements from in situ and in vitro techniques were used. Eleven forages were investigated in vivo using sheep with cannula in the rumen, duodenum and ileum. These forages were fresh, silage and hay from lucerne and orchard grass, and fresh, silage and haylage from red clover, and silage and hay from perennial ryegrass. Digesta flows were measured with the double marker technique using 51Cr-EDTA and 103Ru-phenanthroline. To measure the duodenal flow of microbial nitrogen (N), 15N was infused as well as purine derivatives were measured in urine excretion. In vivo REN, expressed as g N kg-1 of N intake or as g N kg-1 of duodenal flow of non-ammonia N (NAN), was calculated from duodenal flows of NAN and microbial N and with assumptions for the duodenal flow of endogenous N. REN was also estimated from the models estimating effective undegradable N, using measurements from the in situ nylon bag technique or using Cornell net carbohydrate and protein system with data from CPM (Cornell, Penn, Minor Institute) Dairy Beta program (CPM-REN). With the in situ technique REN was calculated from N residues of forages incubated in the rumen, with and without corrections for microbial contamination. These in situ measurements were applied in cows fed a standard diet and in sheep fed the same forage as incubated in the nylon bag. CPM-REN was calculated from five N fractions determined with in vitro techniques. Undegradable N of the 11 forages was measured as N residue after 72 h incubation in nylon bags in the rumen of cows (in situ residual N), after 24 h incubation with protease and as acid detergent insoluble N (ADIN). REN from different in situ measurements and in situ residual N had no relationships with in vivo data. CPM-REN and the in vitro technique using protease had also no relationship with in vivo data. ADIN had a moderate relationship with different in vivo REN determinations and these relations improved when fresh and conserved (silage, hay and haylage) forages were separated (R2 = 0.83–0.87; coefficient of VARIATION = 0.08–0.16). It was concluded, that ADIN has potency to predict in vivo REN of forages.
    Prediction of forage digestibility in ruminants using in situ and in vitro techniques
    Gosselink, J.M.J. ; Dulphy, J.P. ; Poncet, C. ; Jailler, M. ; Tamminga, S. ; Cone, J.W. - \ 2004
    Animal Feed Science and Technology 115 (2004)3-4. - ISSN 0377-8401 - p. 227 - 246.
    nylon bag degradability - gas-production - dry-matter - grass-silage - fermentation characteristics - degradation characteristics - laboratory measurements - cellulase technique - digesta kinetics - voluntary intake
    Two experiments were completed to determine the in vivo digestibility of organic matter (OMD) of forages in sheep. The first experiment was done with 12 forages (database 12) consisting of fresh and conserved forms of lucerne, red clover, orchard grass and perennial ryegrass, fed restricted to sheep. The second experiment was done with 98 forages fed ad libitum to sheep, divided in a database with 37 forages (database 37) with similar qualities as database 12 and a database with 61 forages (database 61). OM and DM digestibility of the forages from these databases was also determined with the in situ nylon bag technique, the pepsin–cellulase technique, the technique of Tilley and Terry and the gas production technique. Database 37 was used to find relationships between OMD and the alternative techniques and between OMD and chemical composition. Databases 12 and 61 were used to validate the observed relationships. The databases were also used to find out if there was an effect of DM intake on the relationships. The OMD predictions by the alternative techniques improved and the effect of DM intake disappeared upon the inclusion of a chemical parameter. The prediction by the in situ technique plus crude protein content showed highest accuracy in the validations, although the four alternative techniques showed similar potency in predicting OMD. The choice of the technique for prediction also depends on other factors, such as animal welfare, price, time, experience and additional information on feed degradation.
    A comparison of in situ and in vitro methods to estimate in vivo fermentable organic matter of forages in ruminants
    Gosselink, J.M.J. ; Dulphy, J.P. ; Poncet, C. ; Tamminga, S. ; Cone, J.W. - \ 2004
    Netherlands Journal of Agricultural Science 52 (2004)1. - ISSN 0028-2928 - p. 29 - 45.
    gas-production profiles - dry-matter - degradation characteristics - grass-silage - dairy-cows - rumen - digestibility - protein - degradability - prediction
    Farmers in five districts of north-eastern Uganda were interviewed to generate information on sweet potato production and constraints, with emphasis on damage by millipedes. Participatory rural appraisal methodology was used to interview 148 farmers. The peak period of planting sweet potato was from the end of May till the beginning of July in order to produce dried form food (amukeke) for storage in the dry season, which sets in around November. Vine cuttings were usually planted on mounds and weeding was mostly done only once. Osukut, Araka Red and Araka White were the most popular varieties. Many respondents obtained planting material from volunteer plants. Separation of plots over time and in space was often not practised. Sweet potato crop rotations were diverse. Millet, groundnut and maize were commonly grown after sweet potato. Cassava, sweet potato, groundnut and maize are host crops for millipedes and were often grown in succession. Millipede incidences were not statistically different for the three agro-ecological zones of north-eastern Uganda, but depended on the frequency of millipede hosts (including sweet potato) in the crop rotations. Groundnut planted after sweet potato had high levels of millipede attack. Millipede incidence was often associated with the incidence of weevils. The results of this inventory show that most farmers consider millipedes as a pest of sweet potato and other major food and cash crops, but that many farmers lack the knowledge to control them.
    Estimation of the duodenal flow of microbial nitrogen in ruminants based on the chemical composition of forages: a literature review
    Gosselink, J.M.J. ; Poncet, C. ; Dulphy, J.P. ; Cone, J.W. - \ 2003
    Animal Research 52 (2003)3. - ISSN 1627-3583 - p. 229 - 243.
    cattle consuming bermudagrass - live-weight-gain - fed beef-cows - oryzae fermentation extract - supplemental cracked corn - dry-matter intake - fed fresh alfalfa - feed-intake - protein-synthesis - dairy-cows
    The objective of this study was to evaluate the estimation of the duodenal flow of microbial nitrogen (N) in ruminants fed forage only, per kilogram of dry matter (DM) intake, which is the yield of microbial protein (YMP). The estimation was based on the chemical composition of forages. A data file of 62 observations was collected from in vivo studies on cattle and sheep fed diets with forage only. A statistical analysis of YMP was conducted with neutral detergent fibre (NDF), crude protein (CP), non structural carbohydrates (NSC), group of forage species (legumes or grasses), method of conservation, physical form of presentation, level of DM intake, animal species, methodology and references as parameters. After a stepwise regression, CP was significant and the most important predictor. NSC or the method of conservation had an extra effect on YMP. On the basis of these three parameters the best fit equations were found and the influence of all parameters on YMP were discussed. Using the data file of this study, the prediction of YMP from the PDI-system was also validated. The statistics of the validation of the PDI prediction were similar to the statistics of the equations from this study. In conclusion, the chemical composition of forages, with or without the method of conservation, is a poor indication for the duodenal flow of microbial N (g $\cdot$kg -1 DM intake) in ruminants fed diets with forages only.
    Adsorption of hydrophobically modified polyacrylic acid on a hydrophobic surface : hysteresis caused by an electrostatic adsorption barrier
    Göbel, J.G. ; Besseling, N.A.M. ; Cohen Stuart, M.A. ; Poncet, C. - \ 1999
    Journal of Colloid and Interface Science 209 (1999). - ISSN 0021-9797 - p. 129 - 135.
    The adsorption of hydrophobically modified polyacrylic acid (HM-PAAc) has been compared to the adsorption of unmodified polymers by means of reflectometry. The polymers were adsorbed onto a noncharged hydrophobic polystyrene surface. The adsorption kinetics of both types of polymer is the same until a certain surface coverage. Then the unmodified sample shows a saturation while the hydrophobically modified polyacrylic acid continues to adsorb. The adsorption behavior of the polyelectrolyte can be controlled by the pH and the ionic strength of the solution. For ionic strengths of 0.001MNaCl the hydrophobically modified polymer shows a larger adsorbed amount at pH 3 to 4 compared to the unmodified polymer. At pH higher than 4 the differences are less significant. At higher ionic strength the amount of adsorbed material increases for both polymers. While doing adsorption–desorption cycles a hysteresis-effect was detected. At the same pH the hydrophobically modified polymer sticks to the surface while the unmodified polymer is already desorbing completely. The hysteresis vanishes when the ionic strength of the solution is increased.
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