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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    Early-life microbiota transplantation affects behavioural responses, serotonin and immune characteristics in chicken lines divergently selected on feather pecking
    Eijk, J.A.J. van der; Rodenburg, T.B. ; Vries, H.J.A. de; Kjaer, J.B. ; Smidt, H. ; Naguib, M. ; Kemp, B. ; Lammers, A. - \ 2020
    Scientific Reports 10 (2020). - ISSN 2045-2322 - 13 p.
    Gut microbiota influences host behaviour and physiology, such as anxiety, stress, serotonergic and immune systems. These behavioural and physiological characteristics are related to feather pecking (FP), a damaging behaviour in chickens that reduces animal welfare and productivity. Moreover, high FP (HFP) and low FP (LFP) lines differed in microbiota composition. However, it is unknown whether microbiota can influence the development of FP. For the first time, we identified the effects of microbiota transplantation on FP, and behavioural and physiological characteristics related to FP. HFP and LFP chicks received sterile saline (control), HFP or LFP microbiota transplantation during the first two weeks post-hatch. Microbiota transplantation influenced behavioural responses of the HFP line during treatment and of the LFP line after treatment. In both lines, homologous microbiota transplantation (i.e., receiving microbiota from their line) resulted in more active behavioural responses. Furthermore, microbiota transplantation influenced immune characteristics (natural antibodies) in both lines and peripheral serotonin in the LFP line. However, limited effects on microbiota composition, stress response (corticosterone) and FP were noted. Thus, early-life microbiota transplantation had immediate and long-term effects on behavioural responses and long-term effects on immune characteristics and peripheral serotonin; however, the effects were dependent on host genotype. Since early-life microbiota transplantation influenced behavioural and physiological characteristics that are related to FP, it could thus influence the development of FP later in life
    Correction to: Functional characterization of genes mediating cell wall metabolism and responses to plant cell wall integrity impairment
    Engelsdorf, Timo ; Kjaer, Lars ; Gigli-Bisceglia, Nora ; Vaahtera, Lauri ; Bauer, Stefan ; Miedes, Eva ; Wormit, Alexandra ; James, Lucinda ; Chairam, Issariya ; Molina, Antonio ; Hamann, Thorsten - \ 2019
    BMC Plant Biology 19 (2019)1. - ISSN 1471-2229 - 1 p.

    Following publication of the original article [1], the author reported that the two curves in the sub-diagram WSR4 in Fig. 2a should be the other way round.

    Functional characterization of genes mediating cell wall metabolism and responses to plant cell wall integrity impairment
    Engelsdorf, Timo ; Kjaer, Lars ; Gigli-Bisceglia, Nora ; Vaahtera, Lauri ; Bauer, Stefan ; Miedes, Eva ; Wormit, Alexandra ; James, Lucinda ; Chairam, Issariya ; Molina, Antonio ; Hamann, Thorsten - \ 2019
    BMC Plant Biology 19 (2019). - ISSN 1471-2229 - 15 p.
    Bioenergy production - Cell wall - Cell wall integrity - Cell wall metabolism - Cell wall signalling - Plant pathogen-interaction

    BACKGROUND: Plant cell walls participate in all plant-environment interactions. Maintaining cell wall integrity (CWI) during these interactions is essential. This realization led to increased interest in CWI and resulted in knowledge regarding early perception and signalling mechanisms active during CWI maintenance. By contrast, knowledge regarding processes mediating changes in cell wall metabolism upon CWI impairment is very limited. RESULTS: To identify genes involved and to investigate their contributions to the processes we selected 23 genes with altered expression in response to CWI impairment and characterized the impact of T-DNA insertions in these genes on cell wall composition using Fourier-Transform Infrared Spectroscopy (FTIR) in Arabidopsis thaliana seedlings. Insertions in 14 genes led to cell wall phenotypes detectable by FTIR. A detailed analysis of four genes found that their altered expression upon CWI impairment is dependent on THE1 activity, a key component of CWI maintenance. Phenotypic characterizations of insertion lines suggest that the four genes are required for particular aspects of CWI maintenance, cell wall composition or resistance to Plectosphaerella cucumerina infection in adult plants. CONCLUSION: Taken together, the results implicate the genes in responses to CWI impairment, cell wall metabolism and/or pathogen defence, thus identifying new molecular components and processes relevant for CWI maintenance.

    Differences in gut microbiota composition of laying hen lines divergently selected on feather pecking
    Eijk, J.A.J. van der; Vries, H.J.A. de; Kjaer, Joergen B. ; Naguib, M. ; Kemp, B. ; Smidt, H. ; Rodenburg, T.B. ; Lammers, A. - \ 2019
    Poultry Science 98 (2019)12. - ISSN 0032-5791 - p. 7009 - 7021.
    Feather pecking (FP), a damaging behavior where laying hens peck and pull at feathers of conspecifics, is multifactorial and has been linked to numerous behavioral and physiological characteristics. The gut microbiota has been shown to influence host behavior and physiology in many species, and could therefore affect the development of damaging behaviors, such as FP. Yet, it is unknown whether FP genotypes (high FP [HFP] and low FP [LFP] lines) or FP phenotypes (i.e., individuals differing in FP, feather peckers and neutrals) differ in their gut microbiota composition. Therefore, we identified mucosa-associated microbiota composition of the ileum and cecum at 10 and 30 wk of age. At 30 wk of age, we further identified luminal microbiota composition from combined content of the ileum, ceca, and colon. FP phenotypes could not be distinguished from each other in mucosa-associated or luminal microbiota composition. However, HFP neutrals were characterized by a higher relative abundance of genera of Clostridiales, but lower relative abundance of Lactobacillus for the luminal microbiota composition compared to LFP phenotypes. Furthermore, HFP neutrals had a higher diversity and evenness for the luminal microbiota compared to LFP phenotypes. FP genotypes could not be distinguished from each other in mucosa-associated microbiota composition. Yet, FP genotypes could be distinguished from each other in luminal microbiota composition. HFP birds were characterized by a higher relative abundance of genera of Clostridiales, but lower relative abundance of Staphylococcus and Lactobacillus compared to LFP birds. Furthermore, HFP birds had a higher diversity and evenness for both cecal mucosa-associated and luminal microbiota compared to LFP birds at adult age. In conclusion, we here show that divergent selection on FP can (in)directly affect luminal microbiota composition. Whether differences in microbiota composition are causal to FP or a consequence of FP remains to be elucidated.
    Stress response, peripheral serotonin and natural antibodies in feather pecking genotypes and phenotypes and their relation with coping style
    Eijk, Jerine A.J. van der; Lammers, Aart ; Kjaer, J.B. ; Rodenburg, T.B. - \ 2019
    Physiology and Behavior 199 (2019). - ISSN 0031-9384 - p. 1 - 10.
    Feather pecking - genotype - natural antibody - phenotype - serotonin - stress response

    Feather pecking (FP), a serious welfare and economic issue in the egg production industry, has been related to coping style. Proactive and reactive coping styles differ in, among others, the stress response, serotonergic activity and immune activity. Yet, it is unknown whether genetic lines divergently selected on FP (i.e. FP genotypes) or individuals differing in FP (i.e. FP phenotypes) can be categorized into coping styles. Therefore, we determined peripheral serotonin (5-HT) levels, natural antibody (NAb) titers, behavioral and corticosterone (CORT) responses to manual restraint (MR) in FP genotypes (high FP (HFP), low FP (LFP) and unselected control (CON) line) and FP phenotypes (feather pecker, feather pecker-victim, victim and neutral). We further examined the consistency of and relationships between behavioral and physiological measures. FP genotypes differed in behavioral responses to MR, 5-HT levels and NAb titers, but not in CORT levels after MR. HFP birds had less active responses at adolescent age, but more active responses at adult age compared to LFP and CON birds. The CON line had higher 5-HT levels at adolescent age, while the HFP line had lower 5-HT levels than the other lines at adult age. Overall, the HFP line had lower IgM NAb titers, while the LFP line had lower IgG NAb titers compared to the other lines. FP phenotypes differed in behavioral responses to MR and 5-HT levels, but not in CORT levels after MR or NAb titers. Within the HFP line, feather peckers tended to have less active responses compared to neutrals at adolescent age, while victims had more active responses compared to the other phenotypes at adult age. Feather peckers had higher 5-HT levels than neutrals at adult age. Behavioral and CORT responses to MR were not consistent over time, suggesting that responses to MR might not reflect coping style in this study. Furthermore, proactive behavioral responses were correlated with reactive physiological measures and vice versa. Thus, it was not possible to categorize FP genotypes or FP phenotypes into specific coping styles.

    LED or HPS in ornamentals? A case study in roses and campanulas
    Ouzounis, Theoharis ; Giday, Habtamu ; Kjaer, Katrine H. ; Ottosen, Carl-Otto - \ 2018
    European Journal of Horticultural Science 83 (2018)3. - ISSN 1611-4434 - p. 166 - 172.
    Energy saving - Greenhouses - Light sources - Ornamentals

    The aim of the experiment was to evaluate the effect of novel top-installed high-output light-emitting diodes (LEDs) on ornamental plant production both in terms of productivity and energy use in comparison with conventional HPS lamps in two standard greenhouse compartments. The experiments were performed in late winter period using three varieties of potted miniature roses (Rosa hybrida) and two cultivars of Campanula grown in identical installed supplemental light levels (75–85 µmol m-2 s-1 of PPFD) with temperature set points 18°C at night, 24°C during the day, while 800 ppm of CO2 was supplied. Due to the winter being relatively cold, the set points were equal to the realized temperature as ventilation rarely occurred. The leaf temperature was maintained at the same level by adjusting the top pipe temperature. Two harvests were performed in February and in March to show the potential effect of winter-or early spring-grown plants. The results showed relatively small differences with respect to plant performance between the HPS and LED treatments, and most significant differences were found only in the 1st batch of roses harvested in February regarding plant height and stem fresh and dry weight, indicating that growth was favored under HPS lamps for three out of four cultivars. Both the 2nd batches for roses and campanulas harvested in March showed very limited or no differences between treatments. The energy saving on the electricity side was 60% in LEDs compared to HPS, but due to the increased heat use from top pipes the energy used for heating increased by around 50% over the whole experimental period.

    Feather pecking genotype and phenotype affect behavioural responses of laying hens
    Eijk, Jerine A.J. van der; Lammers, Aart ; Li, Peiyun ; Kjaer, Joergen B. ; Rodenburg, T.B. - \ 2018
    Applied Animal Behaviour Science 205 (2018). - ISSN 0168-1591 - p. 141 - 150.
    Activity - Coping style - Fearfulness - Feather pecking - Genotype - Phenotype

    Feather pecking (FP) is a major welfare and economic issue in the egg production industry. Behavioural characteristics, such as fearfulness, have been related to FP. However, it is unknown how divergent selection on FP affects fearfulness in comparison to no selection on FP. Therefore, we compared responses of birds selected on low (LFP) and high feather pecking (HFP) with birds from an unselected control line (CON) to several behavioural tests (i.e. novel object (NO), novel environment (NE), open field (OF) and tonic immobility (TI)) at young and adult ages. Furthermore, the relation between actual FP behaviour (i.e. FP phenotypes) and fearfulness is not well understood. Therefore, we compared responses of birds with differing FP phenotypes. Feather pecking phenotypes of individual birds were identified via FP observations at several ages. The number of severe feather pecks given and received was used to categorize birds as feather peckers, feather pecker-victims, victims or neutrals. Here we show that HFP birds repeatedly had more active responses (i.e. they approached a NO sooner, vocalized sooner and more, showed more flight attempts and had shorter TI durations), which could indicate lower fearfulness, compared to CON and LFP birds at both young and adult ages. Within the HFP line, feather peckers had more active responses (i.e. they tended to show more flight attempts compared to victims and tended to walk more compared to neutrals), suggesting lower fearfulness, compared to victims and neutrals. Thus, in this study high FP seems to be related to low fearfulness, which is opposite to what previously has been found in other experimental and commercial lines. This stresses the need for further research into the genetic and phenotypic correlations between FP and fearfulness in various populations of chickens, especially in commercial lines. Findings from experimental lines should be used with caution when developing control and/or prevention methods that are to be applied in commercial settings. Furthermore, activity and/or coping style might overrule fearfulness within the HFP line, as HFP birds and feather peckers within the HFP line had more active responses. This might indicate a complex interplay between fearfulness, activity and coping style that could play a role in the development of FP.

    Allopolyploidization in Cucumis contributes to delayed leaf maturation with repression of redundant homoeologous genes
    Yu, Xiaqing ; Wang, Xixi ; Hyldgaard, Benita ; Zhu, Zaobing ; Zhou, Rong ; Kjaer, Katrine Heinsvig ; Ouzounis, Theoharis ; Lou, Qunfeng ; Li, Ji ; Cai, Qingsheng ; Rosenqvist, Eva ; Ottosen, Carl-Otto ; Chen, Jinfeng - \ 2018
    The Plant Journal 94 (2018)2. - ISSN 0960-7412 - p. 393 - 404.
    The important role of polyploidy in plant evolution is widely recognized. However, many questions remain to be explored to address how polyploidy affects the phenotype of the plant. To shed light on the phenotypic and molecular impacts of allopolyploidy, we investigated the leaf development of a synthesized allotetraploid (Cucumis × hytivus), with an emphasis on chlorophyll development. Delayed leaf maturation was identified in C. × hytivus, based on delayed leaf expansion, initial chlorophyll deficiency in the leaves and disordered sink‐source transition. Anatomical observations also revealed disturbed chloroplast development in C. ×hytivus. The determination of chlorophyll biosynthesis intermediates suggested that the chlorophyll biosynthesis pathway of C. × hytivus is blocked at the site at which uroporphyrinogen III is catalysed to coproporphyrinogen III. Three chlorophyll biosynthesis‐related genes, HEMA1, HEME2 and POR, were significantly repressed in C. × hytivus. Sequence alignment showed both synonymous and non‐synonymous substitutions in the HEMA1, HEME2 and POR genes of the parents. Cloning of the chlorophyll biosynthetic genes suggested the retention of homoeologs. In addition, a chimeric clone of the HEMA1 gene that consisted of homologous genes from the parents was identified in C. × hytivus. Overall, our results showed that allopolyploidization in Cucumis has resulted in disturbed chloroplast development and reduced chlorophyll biosynthesis caused by the repressed expression of duplicated homologous genes, which further led to delayed leaf maturation in the allotetraploid, C. × hytivus. The preferential retention/loss of certain types of genes and non‐reciprocal homoeologous recombination were also supported in the present study, which provides new insights into the impact of allopolyploidy.
    Brain monoamine levels and behaviour of young and adult chickens genetically selected on feather pecking
    Kops, M.S. ; Kjaer, J.B. ; Güntürkün, O. ; Westphal, K.G.C. ; Korte-Bouws, G.A.H. ; Olivier, B. ; Korte, S.M. ; Bolhuis, J.E. - \ 2017
    Behavioural Brain Research 327 (2017). - ISSN 0166-4328 - p. 11 - 20.
    Brain monoamines - Chicken - Development - Dopamine - Genetic selection - Hyperactivity - Laying hen - Poultry welfare - Serotonin - Severe feather pecking

    Severe feather pecking (SFP) in chickens is a detrimental behaviour with possibly neurochemical deficits at its base. Recent neurological studies depicted conflicting results on the role of serotonin (5-hydroxytryptamine, 5-HT) and dopamine (DA) in the development and display of feather pecking. We studied brain monoamine levels and behaviour in domestic chickens divergently genetically selected on feather pecking behaviour, the Low Feather Pecking (LFP) and High Feather Pecking (HFP) lines, both at a young age and when adult, to elucidate the role of 5-HT and DA in feather pecking. Also pecking behaviour and the behavioural response to challenging test situations was determined. At 8 weeks of age, HFP had lower 5-HT and DA turnover in several brain areas than LFP, whereas these differences had disappeared or were even reversed at 25 weeks of age. Line differences in central monoamine activity were found both in emotion-regulating and motor-regulating areas. As expected from previous generations, HFP exceeded LFP in most types of pecking at other birds, including severe feather pecking. Furthermore, HFP responded more actively in most behavioural tests conducted, and seem more impulsive or (hyper)active in their way of coping with challenges. This paper shows different developmental trajectories of the neurochemical systems (5-HT and DA) for chickens divergently selected on feather pecking behaviour, and a remarkable reversion of differences in monoamine activity at a later stage of life. Whether this is a cause or consequence of SFP needs further investigation.

    Omnivores Going Astray: A Review and New Synthesis of Abnormal Behavior in Pigs and Laying Hens
    Brunberg, E.I. ; Rodenburg, T.B. ; Rydhmer, L. ; Kjaer, J.B. ; Jensen, P. ; Keeling, L.J. - \ 2016
    Frontiers in Veterinary Science 3 (2016). - ISSN 2297-1769 - 15 p.
    Pigs and poultry are by far the most omnivorous of the domesticated farm animals and it is in their nature to be highly explorative. In the barren production environments, this motivation to explore can be expressed as abnormal oral manipulation directed toward pen mates. Tail biting (TB) in pigs and feather pecking (FP) in laying hens are examples of unwanted behaviors that are detrimental to the welfare of the animals. The aim of this review is to draw these two seemingly similar abnormalities together in a common framework, in order to seek underlying mechanisms and principles. Both TB and FP are affected by the physical and social environment, but not all individuals in a group express these behaviors and individual genetic and neurobiological characteristics play an important role. By synthesizing what is known about environmental and individual influences, we suggest a novel possible mechanism, common for pigs and poultry, involving the brain–gut–microbiota axis.
    Effects of N fertilization on trichome density, leaf size and artemisinin production in artemisia annua leaves
    Bilkova, I. ; Kjaer, A. ; Kooy, F. van der; Lommen, W.J.M. - \ 2016
    Acta Horticulturae 1125 (2016). - ISSN 0567-7572 - p. 369 - 375.
    Glandular trichomes - Leaf area - Malaria - Microscopy - Nitrogen - Trichomes

    Artemisia annua is currently the only economically viable source of the antimalarial compound artemisinin. Synthesis of artemisinin takes place in glandular trichomes, primarily on the leaves from where artemisinin is extracted. It is not well understood why yields and concentrations of artemisinin vary across crops in relation to external conditions and agricultural practices. We therefore studied the diverse processes underlying artemisinin synthesis in A. annua crops, focussing on effects of |nitrogen fertilization on processes involved in formation of leaves and trichomes, and production of artemisinin in the individual leaves. In two field experiments, effects of nitrogen application levels (0, 75, 175, 400 kg N ha-1) on leaves from a selected position at the main stem and a primary branch were studied. Measurements during part of the life cycle of the leaves included: area and dry weight per leaf, trichome density on the abaxial (lower) leaf side, trichome size, and artemisinin concentration. Results showed that effects of N fertilization were generally small, but in line with the hypothesis that at low N levels individual leaves remain smaller but have higher trichome densities. These trends were especially clear in the branch leaves. The total |number of trichomes per leaf usually increased with increase in N application up to at least 175 kg N ha-1. Within a leaf position, effects of N application on artemisinin concentration in the leaf dry mass were similar to effects on percentage of leaf area covered by trichomes. The total quantity of artemisinin produced per (abaxial) trichome varied, but seemed to decrease linearly with increase in N level. There were no systematic linear or quadratic responses to N application in the total quantity of artemisinin per leaf. The reduction in artemisinin concentration in the leaf mass at higher N levels was therefore caused by increased dry weights per leaf.

    Serotonin release in the caudal nidopallium of adult laying hens genetically selected for high and low feather pecking behavior: An in vivo microdialysis study
    Kops, M.S. ; Kjaer, J.B. ; Güntürkün, O. ; Westphal, K.C.G. ; Korte-Bouws, G.A.H. ; Olivier, B. ; Bolhuis, J.E. ; Korte, S.M. - \ 2014
    Behavioural Brain Research 268 (2014). - ISSN 0166-4328 - p. 81 - 87.
    pigeon columba-livia - gallus-gallus-domesticus - dopaminergic innervation - 5-ht1a receptor - rat-brain - efferent connections - avian telencephalon - aggression - forebrain - chick
    Severe feather pecking (FP) is a detrimental behavior causing welfare problems in laying hens. Divergent genetic selection for FP in White Leghorns resulted in strong differences in FP incidences between lines. More recently, it was shown that the high FP (HFP) birds have increased locomotor activity as compared to hens of the low FP (LFP) line, but whether these lines differ in central serotonin (5-hydroxytryptamine, 5-HT) release is unknown. We compared baseline release levels of central 5-HT, and the metabolite 5-HIAA in the limbic and prefrontal subcomponents of the caudal nidopallium by in vivo microdialysis in adult HFP and LFP laying hens from the ninth generation of selection. A single subcutaneous d-fenfluramine injection (0.5 mg/kg) was given to release neuronal serotonin in order to investigate presynaptic storage capacity. The present study shows that HFP hens had higher baseline levels of 5-HT in the caudal nidopallium as compared to LFP laying hens. Remarkably, no differences in plasma tryptophan levels (precursor of 5-HT) between the lines were observed. d-fenfluramine increased 5-HT levels in both lines similarly indirectly suggesting that presynaptic storage capacity was the same. The present study shows that HFP hens release more 5-HT under baseline conditions in the caudal nidopallium as compared to the LFP birds. This suggests that HFP hens are characterized by a higher tonic 5-HT release.
    High and low feather pecking laying hens differ in both storage and release of central serotonin and dopamine
    Kops, M.S. ; Kjaer, J.B. ; Güntürkün, O. ; Westphal, K.C.G. ; Korte-Bouws, G.A.H. ; Olivier, B. ; Bolhuis, J.E. ; Korte, S.M. - \ 2013
    In: Proceedings of the 11th Dutch EndoNeuroPsycho meeting, 29-31 May 2013, Lunteren, The Netherlands. - - p. 2.26 - 2.26.
    Artemisinin production and precursor ratio in full grown Artemisia annua L. plants subjected to external stress
    Kjaer, A. ; Verstappen, F.W.A. ; Bouwmeester, H.J. ; Ivarsen, E. ; Frette, X. ; Christensen, L.P. ; Grevsen, K. ; Jensen, M. - \ 2013
    Planta 237 (2013). - ISSN 0032-0935 - p. 955 - 966.
    hairy root cultures - dihydroartemisinic acid - glandular trichomes - gene-expression - biosynthesis - accumulation - leaves - cells - identification - improvement
    The concentration of the lifesaving antimalarial compound artemisinin (AN) in cultivated Artemisia annua (A. annua) plants is relatively low, and thus research in improving the content is important. In the present study, external stress was applied to adult plants of A. annua and the effect was examined on the concentrations of AN and its immediate precursors in leaves, and these concentrations were related to densities and sizes of the glandular trichomes (GT). Plants were stress treated weekly five times by sandblasting or spraying with salicylic acid, chitosan oligosaccharide, H2O2, and NaCl solutions. Contents of AN-related compounds (AN-c) were analysed in leaf samples from an upper and a lower position of the plants, and GT were quantified and measured. In lower leaves, several stress treatments had significant negative effects on concentrations of AN-c, whereas the ratios between compounds showed an increased conversion to AN. In the upper leaves, no changes were observed compared to controls. Linear relations were found between the concentrations of metabolites and the density of GT in both upper and lower leaves, and size of GT in lower leaves. Results suggested that older and younger leaves may respond differently to applied stress. A part of the plants were infected by powdery mildew, and this caused significantly different compositions of the AN-c, compared to uninfected plants. In conclusion, changes in concentrations of AN-c seemed largely to be related to changes in GT densities and sizes.
    Poultry welfare and management: WPSA Working Group Nine
    Elson, H.A. ; Jong, I.C. de; Kjaer, J.B. ; Sossidou, E. ; Tauson, R.K. - \ 2012
    Worlds Poultry Science Journal 68 (2012)4. - ISSN 0043-9339 - p. 768 - 775.
    range laying hens - production systems - project
    The introduction of the UK Protection of Animals Act 1911 demonstrates that animal welfare has been of concern for at least a century. The matter came to the fore about 50 years ago, when the welfare of hens in battery cages became an issue. Since then poultry welfare research and the development of superior management and housing systems for poultry have been stimulated by the lobbying of animal welfare organisations along with subsequent policy decisions and legislation. WPSA WG9 was formed in 1972 to encourage scientific studies to inform the poultry welfare debate; its members have positively influenced research and development of welfare-friendly housing systems and husbandry throughout Europe. They have also been active in EU projects aimed at improving the wellbeing of poultry e.g. LayWel, EFSA Opinions and Welfare Quality®. Information derived from such projects has influenced EU Directives and national legislation on the protection and welfare of laying hens and broilers, in particular.
    Nitrogen application to field-grown Artemisia annua affects the leaf area and number of glandular trichomes, but not the density and area of glandular trichomes
    Kjaer, A. ; Lommen, W.J.M. ; Dupré, V.C.F. ; Grevsen, K. ; Jensen, M. - \ 2011
    In: The International Symposium on aromatic and medicinal plants, Chiang Mai, Thailand, 15 - 18 December, 2011. - Chiang Mai, Thailand : - p. 145 - 145.
    The Laywell project: welfare implications of changes in production systems for laying hens
    Blokhuis, H.J. ; Fiks, T.G.C.M. ; Bessei, W. ; Elson, H.A. ; Guémené, D. ; Kjaer, J.B. ; Maria Levrino, G.A. ; Nicol, C.J. ; Tauson, R.K. ; Weeks, C.A. ; Weerd, H.A. v.d. - \ 2007
    Worlds Poultry Science Journal 63 (2007)1. - ISSN 0043-9339 - p. 101 - 114.
    furnished cages - housing systems - priorities - health - size - fear
    The conditions under which laying hens are kept remain a major animal welfare concern. It is one of the most intensive forms of animal production and the number of animals involved is very high. Widespread public debate has stimulated the call for more animal friendly, alternative systems to barren conventional cages. Directive 1999/74/EC has encouraged technical changes in current systems. Not only have traditional cages been modified (so-called 'enriched cages'), but also new alternative systems (e.g. aviaries) have been developed. There is an ongoing need to evaluate the actual welfare status of hens in these novel systems including those on commercial farms. The LayWel project, was funded via the European Commission's Sixth Framework Programme and national funding from several EU countries. Its general objective was to produce an evaluation of the welfare of laying hens in various systems, with special focus on enriched cages, and to disseminate the information in all member states of the EU and associated countries. The project took into account pathological, zootechnical, physiological and ethological aspects. A major achievement of the LayWel project was the compilation of a database collecting data from different housing systems and thus enabling data comparison. The project partners recommend that support is given to maintaining the database in the future so that data can be more reliably modelled. As the type of data collected did not often allow a formal statistical analysis the evaluation of welfare was a presentation of risk factors and advantages and disadvantages of various housing systems. Conclusions are that, with the exception of conventional cages, all systems have the potential to provide satisfactory welfare for laying hens. However this potential is not always realised in practice. Among the numerous explanations are management, climate, design, different responses by different genotypes and interacting effects. A second major achievement of the project was the development of feather scoring and integument (skin, head and feet) scoring systems together with comprehensive sets of photographs. It is recommended that the integument scoring systems are widely adopted and used in on-going research. Farms should also routinely and frequently carry out integument scoring to assist in the detection of damaging pecking, which is currently a widespread welfare problem. Within LayWel an on-farm auditing procedure was developed in the form of a manual for self-assessment. The manual first explains what is meant by welfare and outlines the relevance of welfare assessment. It also summarises risks to welfare in the main categories of housing system. The second part contains recording forms, with guidance for assessing hen welfare. These enable regular checks of a range of indicators of laying hen welfare to be carried out systematically. The indicators were chosen to be relevant to hen welfare as well as feasible and reliable to apply in practice. A series of conclusions and recommendations were made on various aspects of housing systems, behaviour, health and mortality and other matters in relation to bird welfare. Full details of these and all other aspects of the LayWel project can be found on The information is also available on CDROM of which copies are freely available on request.
    Proceedings of the Eleventh International Symposium on Insect-Plant Relationships; August 4-10, 2001, in Helsingør, Denmark
    Nielsen, J.K. ; Kjær, C. ; Schoonhoven, L.M. - \ 2003
    Dordrecht : Kluwer Academic Publishers - ISBN 9781402008900 - 260 p.
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