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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    Interactions between egg storage duration and broiler breeder age on egg fat content, chicken organ weights, and growth performance
    Nasri, Hedia ; Brand, Henry van den; Najjar, Taha ; Bouzouaia, Moncef - \ 2020
    Poultry Science (2020). - ISSN 0032-5791
    breeder age - broiler - chicken quality - egg storage - performance

    Egg storage and breeder age are between the most important factors affecting egg lipids, chicken quality, and posthatch performance. To evaluate these factors, including their interaction, the impact of egg storage duration (5, 12, and 19 D), and breeder age (47 and 67 wk) was investigated in Arbor Acres broiler eggs and chickens. Total yolk fat content, chicken organ development at hatch and at 6 D of age, and posthatch performance (at 7 D and 35 D of age) were determined. Total fat content in fresh yolk was lower in 12 and 19 D stored eggs than in 5 D stored eggs (Δ = −2.42% on average). In hatchlings, the heart percentage was not affected by storage duration in the younger flock but was higher after 19 D than after 5 and 12 D of storage in the old flock (Δ = +0.09% on average). Residual yolk weight was higher after 12 D egg storage than after 5 D egg storage (Δ = +1.7 g), with 19 D egg storage in between. Liver and intestine percentage decreased with storage duration. Residual yolk weight (Δ = +1.09 g) and liver percentage (Δ = +0.18%) were higher in old breeders than in younger breeders. At day 6, chicken BW, yolk free body mass, liver percentage, and intestine percentage interacted between egg storage duration and breeder age with the strongest effects in chickens from older breeder after 19 D of storage. Heart percentage was lower after 19 D compared with 5 and 12 D of storage (Δ = −0.05% on average). Feed intake and feed conversion ratio were higher between day 0 to 7 and 0 to 35 after 19 D than after 5 D egg storage (Δ19-5 D = +12 g and +199 g; +0.11 points and +0.09 points, respectively). It can be concluded that when it is needed, eggs from younger breeders should be stored for a prolonged period (≥12 D) rather than those from older breeders.

    Early life supply of competitive exclusion products reduces colonization of extended spectrum beta-lactamase-producing Escherichia coli in broilers
    Dame-Korevaar, Anita ; Fischer, Egil A.J. ; Goot, Jeanet van der; Velkers, Francisca ; Ceccarelli, Daniela ; Mevius, Dik ; Stegeman, Arjan - \ 2020
    Poultry Science 99 (2020)8. - ISSN 0032-5791 - p. 4052 - 4064.
    antimicrobial resistance - competitive exclusion - ESBL - intervention - pAmpC

    Broilers are an important reservoir of extended spectrum beta-lactamase and AmpC beta-lactamase (ESBL/pAmpC)-producing bacteria. In previous studies, a single supply of a competitive exclusion (CE) product before challenge with a high dose of ESBL/pAmpC-producing Escherichia coli led to reduced colonization, excretion, and transmission, but could not prevent colonization. The hypothesized mechanism is competition; therefore, in this study the effect of a prolonged supply of CE products on colonization, excretion, and transmission of ESBL-producing E. coli after challenge with a low dose at day 0 or day 5 was investigated. Day-old broilers (Ross 308) (n = 220) were housed in isolators. Two CE products, containing unselected fermented intestinal bacteria (CEP) or a selection of pre- and probiotics (SYN), were supplied in drinking water from day 0 to 14. At day 0 or 5, broilers were challenged with 0.5 mL with 101 or 102 cfu/mL E. coli encoding the beta-lactamase gene blaCTX-M-1 on an IncI plasmid (CTX-M-1-E. coli). Presence and concentration of CTX-M-1-E. coli were determined using cloacal swabs (days 0–14, 16, 19, and 21) and cecal content (day 21). Cox proportional hazard model and a mixed linear regression model were used to determine the effect of the intervention on colonization and excretion (log10 cfu/g). When challenged on the day of hatch, no effect of CEP was observed. When challenged at day 5, both CEP and SYN led to a prevention of colonization with CTX-M-1-E. coli in some isolators. In the remaining isolators, we observed reduced time until colonization (hazard ratio between 3.71 × 10−3 and 3.11), excretion (up to −1.60 log10 cfu/g), and cecal content (up to −2.80 log10 cfu/g), and a 1.5 to 3-fold reduction in transmission rate. Colonization after a low-dose challenge with ESBL-producing E. coli can be prevented by CE products. However, if at least 1 bird is colonized it spreads through the whole flock. Prolonged supply of CE products, provided shortly after hatch, may be applicable as an intervention to reduce the prevalence of ESBL/pAmpC-producing bacteria in the broiler production chain.

    Estimating the introduction time of highly pathogenic avian influenza into poultry flocks
    Hobbelen, Peter H.F. ; Elbers, Armin R.W. ; Werkman, Marleen ; Koch, Guus ; Velkers, Francisca C. ; Stegeman, Arjan ; Hagenaars, Thomas J. - \ 2020
    Scientific Reports 10 (2020)1. - ISSN 2045-2322

    The estimation of farm-specific time windows for the introduction of highly-pathogenic avian influenza (HPAI) virus can be used to increase the efficiency of disease control measures such as contact tracing and may help to identify risk factors for virus introduction. The aims of this research are to (1) develop and test an accurate approach for estimating farm-specific virus introduction windows and (2) evaluate this approach by applying it to 11 outbreaks of HPAI (H5N8) on Dutch commercial poultry farms during the years 2014 and 2016. We used a stochastic simulation model with susceptible, infectious and recovered/removed disease stages to generate distributions for the period from virus introduction to detection. The model was parameterized using data from the literature, except for the within-flock transmission rate, which was estimated from disease-induced mortality data using two newly developed methods that describe HPAI outbreaks using either a deterministic model (A) or a stochastic approach (B). Model testing using simulated outbreaks showed that both method A and B performed well. Application to field data showed that method A could be successfully applied to 8 out of 11 HPAI H5N8 outbreaks and is the most generally applicable one, when data on disease-induced mortality is scarce.

    Detection of Low Pathogenic Avian Influenza Virus Subtype H10N7 in Poultry and Environmental Water Samples During a Clinical Outbreak in Commercial Free-Range Layers, Netherlands 2017
    Germeraad, Evelien A. ; Elbers, Armin R.W. ; Bruijn, Naomi D. de; Heutink, Rene ; Voorst, Wendy van; Hakze-van der Honing, Renate ; Bergervoet, Saskia A. ; Engelsma, Marc Y. ; Poel, Wim H.M. van der; Beerens, Nancy - \ 2020
    Frontiers in Veterinary Science 7 (2020). - ISSN 2297-1769
    environmental sampling - LPAIV - outbreak - poultry - water

    Wild birds are the natural reservoir of the avian influenza virus (AIV) and may transmit AIV to poultry via direct contact or indirectly through the environment. In the Netherlands, a clinically suspected free-range layer flock was reported to the veterinary authorities by the farmer. Increased mortality, a decreased feed intake, and a drop in egg production were observed. Subsequently, an infection with low pathogenic avian influenza virus was detected. This study describes the diagnostic procedures used for detection and subtyping of the virus. In addition to routine diagnostics, the potential of two different environmental diagnostic methods was investigated for detecting AIV in surface water. AIV was first detected using rRT-PCR and isolated from tracheal and cloacal swabs collected from the hens. The virus was subtyped as H10N7. Antibodies against the virus were detected in 28 of the 31 sera tested. An intravenous pathogenicity index (IVPI) experiment was performed, but no clinical signs (IVPI = 0) were observed. Post-mortem examination and histology confirmed the AIV infection. Multiple water samples were collected longitudinally from the free-range area and waterway near the farm. Both environmental diagnostic methods allowed the detection of the H10N7 virus, demonstrating the potential of these methods in detection of AIV. The described methods could be a useful additional procedure for AIV surveillance in water-rich areas with large concentrations of wild birds or in areas around poultry farms. In addition, these methods could be used as a tool to test if the environment or free-range area is virus-free again, at the end of an AIV epidemic.

    A review of European models to assess the sustainability performance of livestock production systems
    Linden, Aart van der; Olde, Evelien M. de; Mostert, Pim F. ; Boer, Imke J.M. de - \ 2020
    Agricultural Systems 182 (2020). - ISSN 0308-521X
    Availability - Bio-economic model - Impact assessment - Linear programming - Sustainability indicators

    A large variety of models has been developed to explore the multidimensional, and sometimes conflicting, sustainability consequences of innovations and policies for European livestock farms. Implementation of innovations and policies generally results in both synergies and trade-offs between the environmental, economic, and social dimension of sustainability, and among sustainability themes within these dimensions. An overview of the specific sustainability themes addressed by livestock models is lacking, which hinders the further development of models to evaluate a wide array of sustainability dimensions and themes. The aim of this review, therefore, is to provide an overview of European livestock models that can be used to explore synergies and trade-offs among sustainability themes. This systematic literature review yielded 215 European livestock models at the animal level, herd or flock level and farm level. Models were mainly developed in Western Europe, and may have, therefore, a reduced accuracy when applied to other regions than Western Europe. Most models cannot assess a wide array of synergies and trade-offs among sustainability dimensions and themes, as only 33% covered all three sustainability dimensions. Models addressed four sustainability themes on average. Social themes are often lacking in models and additional efforts are needed to develop more integrative models by adapting and extending existing models, especially for monogastric animals. Adaptation and extension of existing models is facilitated by improving the availability of livestock models, increasing the percentage of livestock models published open source, collaborating on the development of joint and generic models and by improving descriptions of the programming languages and programs used and the stakeholders involved. This model review can be used to identify which models or combinations of models are best suited to explore the sustainability consequences of innovations and policies for livestock farms in Europe.

    Method and system for grading hens in a flock
    Hogewerf, P.H. - \ 2020
    Octrooinummer: WO2020009578, gepubliceerd: 2020-01-09.
    The invention pertains to a method for grading individual poultry hens in a flock, wherein the method comprises the following steps: - when a hen is present in or adjacent to a laying nest, applying a mark to that hen, which mark is invisible to the hens of the flock, - after a marking time period which is at least as long as the expected time interval between the laying of two subsequent eggs by a single hen, determining which hens of the flock do not have a mark, therewith grading the hens into a first class of hens which have at least one mark and a second class of hens which do not have a mark.
    Relative contribution of production chain phases to health and performance of broiler chickens : a field study
    Jong, Ingrid C. de; Riel, Johan W. van - \ 2020
    Poultry Science 99 (2020)1. - ISSN 0032-5791 - p. 179 - 188.
    broiler - broiler breeder - health - performance - production chain data

    There is increasing evidence that health and performance of the breeder flock significantly contributes to health and performance of their progeny. Data of broiler performance and health are routinely collected in various stages of the broiler production chain. In the Netherlands, the broiler chain operates at a relatively non-integrated level and the various databases are usually not connected. Connecting databases may however provide important information to improve chain performance. The aim of the present study was to determine systematic effects of broiler breeder production farm or flock on health (mortality and antibiotics use) and performance of their offspring, using data routinely collected at the different stages of the production chain. Broiler flock data collected over 6 yr (daily growth, slaughter weight, carcass weight uniformity, carcass condemnations, first week and total mortality, and antibiotics use) were linked to breeder flocks and farms. In total, 2,174 broiler flock records (at house level) of 74 broiler farms were linked to 88 broiler breeder farms and 209 breeder flocks. A mixed model analysis was applied to simultaneously estimate effects of season, parent flock age, time trend, and the contribution of the different chain phases to broiler performance and health. No systematic effects of breeder farm and only small systematic effects of breeder flock on broiler health and performance were found. The largest breeder flock effect was found for carcass condemnations (estimated contribution to the variance component: 7%). Most variation on broiler health and performance was explained by broiler farm and “day-old chick batch.” The latter refers to the rest variance that could not be explained by other factors, i.e., incidental effects linked to the specific day-old chick batch and the stage between the breeder and broiler farm. Our results suggest that systematic effects of breeder flock and farm could have been overruled by (management in) the hatchery phase and the broiler farm. This indicates room for improvement of management in these production phases.

    Evidence-based management of injurious pecking.
    Niekerk, T. van - \ 2019
    In: Poultry Feathers and Skin: The Poultry Integument in Health and Welfare / Olukosi, O.A., Olori, V.E., Helmbrecht, A., Lambton, S., French, N.A., CABI - ISBN 9781786395115 - p. 57 - 69.
    Injurious pecking in laying hen flocks comprises feather pecking and tissue pecking, the latter often referred to as cannibalism. Although some gentle feather pecking belongs to the natural repertoire of laying hens, the more vigorous form, severe feather pecking, is considered an abnormal behaviour. Various theories have been developed to explain the onset of injurious pecking. All point to suboptimal circumstances leading to abnormal or redirected behaviour. A wide range of husbandry and management factors have been identified. They affect either the onset of injurious pecking (prevention) or its reduction. Prevention is most important, because once started the behaviour is very hard to stop. Therefore the first focus should be on optimizing rearing conditions to prevent injurious pecking. The most important management strategy in rear is a continuous presence of high-quality substrate to stimulate foraging behaviour and to allow the pullets to develop a habit of directing their pecking towards the litter. Any stressor can be a trigger for injurious pecking. This means management should also focus on the prevention of stressful events. Such stressful events may be changes in housing conditions (e.g. transition from rear to lay, climate) and management (e.g. light, feed, access to range), but also suboptimal health, especially parasites and compromised intestinal health. Finally some husbandry conditions seem to increase the propensity to develop injurious pecking, such as large flock sizes and a higher bird density. Management to prevent injurious pecking can only be successful if it aims at optimizing all factors involved
    Automated monitoring of broilers from different hatching conditions: the HealthyLivestock approach
    Giersberg, M.F. ; Molenaar, R. ; Jong, I.C. de; Souza da Silva, Carol ; Brand, H. van den; Kemp, B. ; Rodenburg, T.B. - \ 2019
    In: Book of Abstracts of the 70th Annual Meeting of the European Federation of Animal Science Book of abstracts No. 25 (2019). - Wageningen : Wageningen Academic Publishers (EAAP Book of Abstracts ) - ISBN 9789086863396 - p. 389 - 389.
    The early peri-hatching environment has effects on the health, resilience and welfare of broiler chickens in later life. Optimal early and later life conditions in combination with reliable automated flock monitoring systems will likely contribute to a reduction in the use of antimicrobials in broiler production. The aim of this study is to investigate if recently developed hatching systems promote health and welfare in broiler chickens, and to validate a PLF tool to monitor these parameters automatically. Therefore, a grow-out experiment with chickens from three different hatching conditions is performed. The chickens are hatched either conventionally (no light, feed or water in the hatcher), in a system which provides feed and water in the hatcher (HatchCare, HatchTech) or on-farm (X-treck,
    Vencomatic), where feed and water is available after hatch and, in addition, transport of day-old chickens from
    hatcher to farm is not necessary. The animals are housed in a total of 12 floor pens (1,150 animals/pen) with four
    replications of each treatment. Each pen is equipped with a camera of the eYeNamic system (Fancom) taking topview images of the flocks. A customized software program translates these images into indices for animal distribution and activity, which are valuable indicators for leg and food pad health. Furthermore, changes in flock activity after inspections rounds by farm staff may be used to measure the animals’ fear responses towards humans automatically.
    In order to validate this PLF tool and to investigate whether it is capable to detect also small differences between the treatment groups, the broilers’ health and welfare are assessed manually by means of established scoring protocols. The experiment will be finished at the end of Spring 2019. All data analyses will be completed, and the results will be presented at the EAAP conference.
    Effect of challenge dose of plasmid-mediated extended-spectrum β-lactamase and AmpC β-lactamase producing Escherichia coli on time-until-colonization and level of excretion in young broilers
    Dame-Korevaar, Anita ; Fischer, Egil A.J. ; Goot, Jeanet van der; Velkers, Francisca ; Broek, Jan van den; Veldman, Kees ; Ceccarelli, Daniela ; Mevius, Dik ; Stegeman, Arjan - \ 2019
    Veterinary Microbiology 239 (2019). - ISSN 0378-1135
    Animal model - Antibiotic resistance - Dose-response - Inoculation - Poultry - Transmission

    Plasmid-mediated extended-spectrum β-lactamase and AmpC β-lactamase (ESBL/pAmpC) producing bacteria are present at all levels of the broiler production pyramid. Young birds can be found positive for ESBL/pAmpC-producing Escherichia coli shortly after arrival at farm. The aim of this study was to determine the effect of different challenge doses of ESBL/pAmpC-producing E. coli on time-until-colonization and the level of excretion in young broilers. One-day-old broilers (specific-pathogen free (SPF) and conventional Ross 308) were housed in isolators and challenged with 0.5 ml ESBL/pAmpC-producing E. coli strains of varying doses (101–105 CFU/ml). Presence and concentration (CFU/gram feces) of ESBL/pAmpC-producing E. coli and total E. coli were determined longitudinally from cloacal swabs, and in cecal content 72 h after challenge. Higher challenge doses resulted in shorter time-until-colonization. However, even the lowest dose (101 CFU/ml) resulted in colonization of the broilers which excreted >106 CFU/gram feces 72 h after inoculation. Conventional broilers were colonized later than SPF broilers, although within 72 h after challenge all broilers were excreting ESBL/pAmpC-producing E. coli. A probabilistic model was used to estimate the probability of colonization by initial inoculation or transmission. The higher the dose the higher the probability of excreting ESBL/pAmpC-producing E. coli as a result of inoculation. In conclusion, low initial doses of ESBL/pAmpC-producing E. coli can result in rapid colonization of a flock. Interventions should thus be aimed to eliminate ESBL/pAmpC-producing bacteria in the environment of the hatchlings and measures focusing at reducing colonization and transmission of ESBL/pAmpC-producing E. coli should be applied shortly after hatching.

    Broiler welfare trade-off: A semi-quantitative welfare assessment for optimised welfare improvement based on an expert survey
    Bracke, Marc B.M. ; Koene, Paul ; Estevez, Inma ; Butterworth, Andy ; Jong, Ingrid C. de - \ 2019
    PLoS ONE 14 (2019)10. - ISSN 1932-6203

    In order to support decision making on how to most effectively improve broiler welfare an innovative expert survey was conducted based on principles derived from semantic modelling. Twenty-seven experts, mainly broiler welfare scientists (n = 20; and 7 veterinarians), responded (response rate 38%) by giving welfare scores (GWS, scale 0–10) to 14 benchmarking housing systems (HSs), and explaining these overall scores by selecting, weighing and scoring main welfare parameters, including both input and output measures. Data exploration followed by REML (Linear Mixed Model) and ALM (Automatic Linear Modelling) analyses revealed 6 clusters of HSs, sorted from high to low welfare, i.e. mean GWS (with superscripts indicating significant differences): 1. (semi-natural backyard) Flock (8.8a); 2. Nature (7.7ab), Label Rouge II (7.4ab), Free range EU (7.2ab), Better Life (7.2ab); 3. Organic EU (7.0bc), Freedom Food (6.2bc); 4. Organic US (5.8bcd), Concepts NL (5.6abcdef), GAP 2 (4.9bcd); 5. Conventional EU (3.7de), Conventional US (2.9ef), Modern cage (2.9abcdef); 6. Battery cage (1.3f). Mean weighting factors (WF, scale 0–10) of frequently (n> = 15) scored parameters were: Lameness (8.8), Health status (8.6), Litter (8.3), Density (8.2), Air quality (8.1), Breed (8.0), Enrichment (7.0) and Outdoor (6.6). These did not differ significantly, and did not have much added value in explaining GWS. Effects of Role (Scientist/Vet), Gender (M/F) and Region (EU/non-EU) did not significantly affect GWS or WF, except that women provided higher WF than men (7.2 vs 6.4, p<0.001). The contribution of welfare components to overall welfare has been quantified in two ways: a) using the beta-coefficients of statistical regression (ALM) analyses, and b) using a semantic-modelling type (weighted average) calculation of overall scores (CalcWS) from parameter level scores (PLS) and WF. GWS and CalcWS were highly correlated (R = ~0.85). CalcWS identified Lameness, Health status, Density, Breed, Air quality and Litter as main parameters contributing to welfare. ALM showed that the main parameters which significantly explained the variance in GWS based on all PLS, were the output parameter Health status (with a beta-coefficient of 0.38), and the input parameters (stocking) Density (0.42), Litter (0.14) and Enrichment (0.27). The beta-coefficients indicated how much GWS would improve from 1 unit improvement in PLS for each parameter, thus the potential impact on GWS ranged from 1.4 welfare points for Litter to 4.2 points for Density. When all parameters were included, 81% of the variance in GWS was explained (77% for inputs alone; 39% for outputs alone). From this, it appears that experts use both input and output parameters to explain overall welfare, and that both are important. The major conventional systems and modern cages for broilers received low welfare scores (2.9–3.7), well below scores that may be considered acceptable (5.5). Also, several alternatives like GAP 2 (4.9), Concepts NL (5.6), Organic US (5.8) and Freedom Food (6.2) are unacceptable, or at risk of being unacceptable due to individual variation between experts and farms. Thus, this expert survey provides a preliminary semi-quantified decision-support tool to help determine how to most effectively improve broiler welfare in a wide range of HSs.

    Associations between carcass weight uniformity and production measures on farm and at slaughter in commercial broiler flocks
    Vasdal, Guro ; Granquist, Erik Georg ; Skjerve, Eystein ; Jong, Ingrid C. de; Berg, Charlotte ; Michel, Virginie ; Moe, Randi Oppermann - \ 2019
    Poultry Science 98 (2019)10. - ISSN 0032-5791 - p. 4261 - 4268.
    chicken - health - indicator - poultry - welfare

    In poultry flocks, flock weight uniformity is often defined as the percent individuals within 10% of the mean body weight (BW) and the variability of this uniformity can be expressed as the CV of BW. Flock weight uniformity is a standardized and objective measured, and could potentially be used as a welfare indicator; however, little is known about the relationship between flock uniformity and other production measures on-farm or at slaughter. The aim of this study was to investigate the associations between carcass weight uniformity (CV of BW) and production measures on-farm and at slaughter in Norwegian commercial broiler flocks. A total of 45 randomly selected mixed-sex Ross 308 broiler flocks were visited prior to slaughter at 28 to 30 D of age (average slaughter age 30.6 D). All flocks were raised under similar farm management systems. The Welfare Quality protocol for broilers was used to assess different animal welfare indicators in each flock. All production data from the slaughterhouse were collected for each flock, including carcass weight uniformity (%), mortality (%), growth rate (g), feed conversion ratio (FCR), and rejected birds (%) in different rejection categories. Univariable and multivariable linear regression models were used to investigate the associations between flock weight uniformity and production and welfare measures. The results showed that flock uniformity varied from 11% to 18% between flocks within the same hybrid, similar management standards, and similar slaughter age (day 29 to 32). Poorer uniformity (i.e., high CV) was associated with increased first week mortality (P < 0.004, r = 1.48, increased total mortality (P < 0.013, r = 0.01), increased FCR (i.e., less efficient growth) (P < 0.024, r = 0.06), reduced growth rate (P < 0.0012, r = -0.01), and a reduced rejection rate at slaughter (P < 0.006, r = -0.01). The results show that flock uniformity varies across broiler flocks, and is associated with several production measures.

    Associations between antimicrobial use and the faecal resistome on broiler farms from nine European countries
    Luiken, Roosmarijn E.C. ; Gompel, Liese Van; Munk, Patrick ; Sarrazin, Steven ; Joosten, Philip ; Dorado-García, Alejandro ; Borup Hansen, Rasmus ; Knudsen, Berith E. ; Bossers, Alex ; Wagenaar, Jaap A. ; Aarestrup, Frank M. ; Dewulf, Jeroen ; Mevius, Dik J. ; Heederik, Dick J.J. ; Smit, Lidwien A.M. ; Schmitt, Heike - \ 2019
    Journal of Antimicrobial Chemotherapy 74 (2019)9. - ISSN 0305-7453 - p. 2596 - 2604.

    OBJECTIVES: To determine associations between farm- and flock-level antimicrobial usage (AMU), farm biosecurity status and the abundance of faecal antimicrobial resistance genes (ARGs) on broiler farms. METHODS: In the cross-sectional pan-European EFFORT study, conventional broiler farms were visited and faeces, AMU information and biosecurity records were collected. The resistomes of pooled faecal samples were determined by metagenomic analysis for 176 farms. A meta-analysis approach was used to relate total and class-specific ARGs (expressed as fragments per kb reference per million bacterial fragments, FPKM) to AMU (treatment incidence per DDD, TIDDDvet) per country and subsequently across all countries. In a similar way, the association between biosecurity status (Biocheck.UGent) and the resistome was explored. RESULTS: Sixty-six (38%) flocks did not report group treatments but showed a similar resistome composition and roughly similar ARG levels to antimicrobial-treated flocks. Nevertheless, we found significant positive associations between β-lactam, tetracycline, macrolide and lincosamide, trimethoprim and aminoglycoside antimicrobial flock treatments and ARG clusters conferring resistance to the same class. Similar associations were found with purchased products. In gene-level analysis for β-lactams and macrolides, lincosamides and streptogramins, a significant positive association was found with the most abundant gene clusters blaTEM and erm(B). Little evidence was found for associations with biosecurity. CONCLUSIONS: The faecal microbiome in European broilers contains a high diversity of ARGs, even in the absence of current antimicrobial selection pressure. Despite this, the relative abundance of genes and the composition of the resistome is positively related to AMU in European broiler farms for several antimicrobial classes.

    Estimating within-flock transmission rate parameter for H5N2 highly pathogenic avian influenza virus in Minnesota turkey flocks during the 2015 epizootic
    Ssematimba, A. ; Malladi, S. ; Hagenaars, T.J. ; Bonney, P.J. ; Weaver, J.T. ; Patyk, K.A. ; Spackman, E. ; Halvorson, D.A. ; Cardona, C.J. - \ 2019
    Epidemiology and Infection 147 (2019). - ISSN 0950-2688
    Analysis of data - avian flu - mathematical modelling - veterinary epidemiology

    Better control of highly pathogenic avian influenza (HPAI) outbreaks requires deeper understanding of within-flock virus transmission dynamics. For such fatal diseases, daily mortality provides a proxy for disease incidence. We used the daily mortality data collected during the 2015 H5N2 HPAI outbreak in Minnesota turkey flocks to estimate the within-flock transmission rate parameter (β). The number of birds in Susceptible, Exposed, Infectious and Recovered compartments was inferred from the data and used in a generalised linear mixed model (GLMM) to estimate the parameters. Novel here was the correction of these data for normal mortality before use in the fitting process. We also used mortality threshold to determine HPAI-like mortality to improve the accuracy of estimates from the back-calculation approach. The estimated β was 3.2 (95% confidence interval (CI) 2.3-4.3) per day with a basic reproduction number of 12.8 (95% CI 9.2-17.2). Although flock-level estimates varied, the overall estimate was comparable to those from other studies. Sensitivity analyses demonstrated that the estimated β was highly sensitive to the bird-level latent period, emphasizing the need for its precise estimation. In all, for fatal poultry diseases, the back-calculation approach provides a computationally efficient means to obtain reasonable transmission parameter estimates from mortality data.

    Poultry husbandry, water, sanitation, and hygiene practices, and child anthropometry in rural Burkina Faso
    Gelli, Aulo ; Headey, Derek ; Becquey, Elodie ; Ganaba, Rasmane ; Huybregts, Lieven ; Pedehombga, Abdoulaye ; Santacroce, Marco ; Verhoef, Hans - \ 2019
    Maternal and Child Nutrition 15 (2019)4. - ISSN 1740-8695
    hygiene - nutrition - poultry

    Poultry production in low income countries provides households with nutrient-rich meat and egg products, as well as cash income. However, traditional production systems present potential health and nutrition risks because poultry scavenging around household compounds may increase children's exposure to livestock-related pathogens. Data from a cross-sectional survey were analysed to examine associations between poultry, water, sanitation, and hygiene practices, and anthropometric indicators in children (6–59 months; n = 3,230) in Burkina Faso. Multilevel regression was used to account for the hierarchical nature of the data. The prevalence of stunting and wasting in children 6–24 months was 19% and 17%, respectively, compared with a prevalence of 26% and 6%, respectively, in children 25–60 months. Over 90% of households owned poultry, and chicken faeces were visible in 70% of compounds. Caregivers reported that 3% of children consumed eggs during a 24-hr recall. The presence of poultry faeces was associated with poultry flock size, poultry-husbandry and household hygiene practices. Having an improved water source and a child visibly clean was associated with higher height-for-age z scores (HAZ). The presence of chicken faeces was associated with lower weight-for-height z scores, and no associations were found with HAZ. Low levels of poultry flock size and poultry consumption in Burkina Faso suggest there is scope to expand production and improve diets in children, including increasing chicken and egg consumption. However, to minimize potential child health risks associated with expanding informal poultry production, research is required to understand the mechanisms through which cohabitation with poultry adversely affects child health and design interventions to minimize these risks.

    The possible side-effect of two different drinking water additives on control of the poultry red mite : The effect of suppleting the products Alphamites DW and Hensupp+ on the Dermanyssus gallinae adult’s ability to produce eggs and the ability of nymphs of Dermanyssus gallinae to moult
    Mul, M.F. ; Binnendijk, G.P. ; Riel, J.W. van; Wikselaar, G.P. van - \ 2019
    Wageningen : Wageningen Livestock Research (Wageningen Livestock Research report 1098) - 18
    In laying hen facilities drinking water additives are used to support the hens natural resistance. It seems that these productshave a side-effect on the life cycle of the ecto-parasitic miteDermanyssus gallinae; either because mites do not approach the laying hens by the products repellent effects or by making the blood indigestible for the poultry red mite. Whether these products do need a registration as veterinary medicine or as biocide was not the subject of this study. The aim ofthis studywas to test the effect ofHensupp+ and Alphamites DWon D. gallinaefemale adults’ability to lay eggs and on the D. gallinaenymphs’ability to moult. Here we measuredindirect the effect of the products onthe lifecycle of D. gallinae. D. gallinaemites were collected at 3 commercial farms using Alphamites DW and at 4 commercialfarms using Hensupp+. Mites were also collected at a commercial control farm where no water additives were used, but only a silica product to control D. gallinae. Recently engorged female adults and nymphs were individually placed in 96 well plates enabling to determine mite egg production or moulting. No significant differences were found in the percentage of adult mites producing eggs or the percentage of moulting nymphs of the collected mites from the farms with drinking water additives, compared to the mites from the control farm. A trend however was seen for a lower percentage of moulting nymphs from farms which supplyAlphamites DW compared to the percentage of moultingnymphs from the control farm.This observational studywas carried out at seven commercial farms of which it can be expected that they carried outthe advised treatment protocol, but of which we are not sure. Neither do we know if there werefactors present (such as health status of the flock and water and feed quality)which could have influenced the test results. In this test, we determined a small part of the possible effects of the two drinking water additives on red mites and therefore we are not able to draw conclusions about the total effect of the two water additives on the poultry red mite.
    Lameness and its relationship with health and production measures in broiler chickens
    Granquist, E.G. ; Vasdal, G. ; Jong, I.C. De; Moe, R.O. - \ 2019
    Animal 13 (2019)10. - ISSN 1751-7311 - p. 2365 - 2372.
    condemnation - dermatitis - gait - poultry - welfare

    The aim of this study was to explore lameness and the associations between lameness and health/production measures of animal welfare in commercial broiler production, using the Welfare Quality ® protocol for broilers. A total of 50 flocks were included in the sample and farm visits were conducted for lameness scoring at a mean age of 28.9 days. The percentage of animals (n=7500) in the six different gait score (GS) categories were GS0: 2.53%, GS1: 44.19%, GS2: 33.84%, GS3: 16.32%, GS4: 2.36% and GS5: 0.53%. Production and other welfare data were collected for each flock after slaughter. Higher gait scores were associated with increased hock burn score (P<0.02), increased footpad dermatitis score (P<0.01), reduced bird cleanliness score (P<0.01) and peat litter (P<0.01). Although not statistically significant, there was a tendency for increased flock gait score being associated with wet litter (P=0.07). In addition, condemnations at postmortem inspection were associated with increasing gait scores (P<0.05), indicating that at least a portion of the lameness cases display pathological changes on the carcasses. In conclusion, 19%of the birds showed moderate-to-severe lameness, which was associated with several production or health and welfare observations including feather cleanliness and condemnations as unfit for human consumption at slaughter. Although stocking density and growth rate are already known key factors for lameness, associations of lameness with hock burns, footpad dermatitis and cleanliness of the birds suggest that a suboptimal physical environment (e.g. litter- and air quality) may be detrimental to leg health. Further studies are needed to explore these associations in more detail.

    From green to transparent waters : Managing eutrophication and cyanobacterial blooms by geo-engineering
    Mucci, Maíra N.T. - \ 2019
    Wageningen University. Promotor(en): M.F.L.L.W. Lürling, co-promotor(en): E.J. Faassen; M. Manzi. - Wageningen : Wageningen University - ISBN 9789463434416 - 200

    Eutrophication and cyanobacterial blooms are increasing worldwide. Despite being studied for almost a century, mitigating eutrophication remains a challenge. Motivated by this challenge, we studied potential geo-engineering materials and in-site techniques to manage the eutrophication and cyanobacterial blooms in controlled experiments and a whole-ecosystem intervention.

    As phosphorus (P) control is essential to manage eutrophication, this thesis started evaluating natural and modified clays and soils for their capacity to adsorb P (chapter 2). We showed that four out of ten materials were able to adsorb P, and that P adsorption differed under varying abiotic conditions. The modified materials (lanthanum (La) modified bentonite, commercially called Phoslock® and Aluminium modified zeolite, commercially called Aqual-P®) were able to adsorb more P than the naturals ones such as Fe-rich soils

    The need to mitigate eutrophication in coastal areas prompted us to evaluate Phoslock® efficiency and behaviour in saline waters in chapter 3. Phoslock® was able to adsorb P in all salinities tested from brackish to seawater, whilst filterable La concentrations remained very low. We concluded that the use of Phoslock® on saline waters should be considered, yet, ecotoxicological studies must be performed before field applications in saline environments.

    Beside solid-phase P sorbents, flocculants have also been used in lake restoration. In this context, chitosan has been proposed as an “eco-friendly” flocculant as an alternative to metal based flocculant, such as polyaluminium chloride (PAC). In chapter 4, we tested the effect of chitosan on several cyanobacterial species and showed that chitosan may cause rapid cell lysis. In chapter 5, we looked closer into strain variation whilst also measuring cyanotoxin release. We showed that chitosan was able to cause cyanotoxins release. These effects were, however, strain dependent. Chitosan application might therefore cause toxin release in the water column, and it should not therefore be used without testing its effects on the cyanobacterial assemblage being targeted to avoid unwanted rapid release of cyanotoxins.

    In chapter 6, we showed field results from a whole-lake treatment with PAC and Phoslock®. This technique called Flock and Lock aimed to target P from the water column, P-release from the sediment and the ongoing cyanobacterial bloom. The intervention was successful in improving water quality in Lake De Kuil. After two

    weeks of the treatment, however a surface scum was observed near the shore of the lake, which disappeared spontaneously after two weeks. The lake was open in time for the bathing season without any swimming bans during 2017. Tests to why the scums occurred, and how to avoid their occurrence showed that promising approach to avoid biomass accumulation is to damage the cell first using hydrogen peroxide and later settle them with the Flock and Lock technique. Larger scales tests need still to be performed to shed light on possible limitations of this technique.

    In chapter 7 I reflected that there is no single magical solution to manage eutrophication and cyanobacterial blooms. Each system is unique and each material/technique (P immobilization, chitosan, Flock and Lock, peroxide) has its limitations. Thus, a broad-scale generalization (copy-paste of methods) will in most cases not lead to a successful restoration. A mitigation plan must always include a proper system analysis and experimental tests under realistic condition on various scales before a field application can be performed.

    Mosquito Small RNA Responses to West Nile and Insect-Specific Virus Infections in Aedes and Culex Mosquito Cells
    Göertz, Giel P. ; Miesen, Pascal ; Overheul, Gijs J. ; Rij, Ronald P. van; Oers, Monique M. van; Pijlman, Gorben P. - \ 2019
    Viruses 11 (2019)3. - ISSN 1999-4915
    de novo assembly - insect-specific viruses - mosquito cells - next-generation sequencing - PIWI-interacting RNAs - RNAi - small RNA - small-interfering RNAs - virus discovery - West Nile virus

    Small RNA mediated responses are essential for antiviral defence in mosquitoes, however, they appear to differ per virus-vector combination. To further investigate the diversity of small RNA responses against viruses in mosquitoes, we applied a small RNA deep sequencing approach on five mosquito cell lines: Culex tarsalis CT cells, Aedes albopictus U4.4 and C6/36 cells, Ae. aegypti Aag2 cells (cleared from cell fusing agent virus and Culex Y virus (CYV) by repetitive dsRNA transfections) and Ae. pseudoscutellaris AP-61 cells. De novo assembly of small RNAs revealed the presence of Phasi Charoen-like virus (PCLV), Calbertado virus, Flock House virus and a novel narnavirus in CT cells, CYV in U4.4 cells, and PCLV in Aag2 cells, whereas no insect-specific viruses (ISVs) were detected in C6/36 and AP-61 cells. Next, we investigated the small RNA responses to the identified ISVs and to acute infection with the arthropod-borne West Nile virus (WNV). We demonstrate that AP-61 and C6/36 cells do not produce siRNAs to WNV infection, suggesting that AP-61, like C6/36, are Dicer-2 deficient. CT cells produced a strong siRNA response to the persistent ISVs and acute WNV infection. Interestingly, CT cells also produced viral PIWI-interacting (pi)RNAs to PCLV, but not to WNV or any of the other ISVs. In contrast, in U4.4 and Aag2 cells, WNV siRNAs, and pi-like RNAs without typical ping-pong piRNA signature were observed, while this signature was present in PCLV piRNAs in Aag2 cells. Together, our results demonstrate that mosquito small RNA responses are strongly dependent on both the mosquito cell type and/or the mosquito species and family of the infecting virus.

    Correlating farmers' perception and sheep preference with the nutritional quality of grain legume fodders stored under different conditions
    Akakpo, Daniel ; Oosting, S.J. ; Adjei-nsiah, Samuel ; Duncan, A. ; Boer, I.J.M. de; Giller, K.E. - \ 2019
    In: Trade-Offs in Science - Keeping the balance. - Wageningen University & Research - p. 20 - 20.
    The objective of the present study was to correlate farmers’ perception (FP), sheep preference (SP) and laboratory analysis (LA) of nutritional quality of stored grain legume fodders (GLFs). The GLFs of cowpea, groundnut and soybean were stored at 3-locations (rooftop, room and treefork) in -packaging types (polythene sacks or tied with ropes) for 120 days. FP was assessed by scoring the perceived quality of GLFs on a scale of 1 to 10 (1=bad and 0=good) based on physical appraisal by a group of farmers. SP was assessed by cafeteria feeding trial based on dry matter intake (DMI) of GLFs by a flock of 12 sheep during a 14 hr period. For LA, Organic Matter Digestibility (OMD) and Crude Protein (CP) content were assessed by Near Infra-Red Spectroscopy (NIRS). Cowpea scored higher FP (6.3) and SP (66 g DMI/14hr/sheep) than
    groundnut (FP 5.5 and SP 59 g DMI/14hr/sheep) and soybean had lowest FP (2.3) and SP (39 g DMI/14hr/sheep). However, LA indicated that groundnut had higher CP content (140 g kg DM) than cowpea (115 g kg DM) and soybean (98 g kg DM). OMD, on the other hand, was higher in cowpea (686 g kg DM) than groundnut (659 g kg DM) and soybean (574 g kg DM). CP was positively orrelated with FP (r=0.35) and with SP (r=0.48). Similarly, OMD was positively correlated with FP (r=0.50) and with SP (r=0.70). Room storage had higher FP and SP than rooftop and treefork. Sack storage scored higher than tied on FP, SP and LA. The present study demonstrated that it is possible to used FP and SP to predict the nutritional quality of GLFs.
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