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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    Changes in in vitro gas and methane production from rumen fluid from dairy cows during adaptation to feed additives in vivo
    Klop, G. ; Laar-van Schuppen, S. van; Pellikaan, W.F. ; Hendriks, W.H. ; Bannink, A. ; Dijkstra, Jan - \ 2017
    Animal 11 (2017)4. - ISSN 1751-7311 - p. 591 - 599.
    adaptation - dairy cows - essential oils - lauric acid - methane
    The adaptation of dairy cows to methane (CH4)-mitigating feed additives was evaluated using the in vitro gas production (GP) technique. Nine rumen-fistulated lactating Holstein cows were grouped into three blocks and within blocks randomly assigned to one of three experimental diets: Control (CON; no feed additive), Agolin Ruminant® (AR; 0.05 g/kg dry matter (DM)) or lauric acid (LA; 30 g/kg DM). Total mixed rations composed of maize silage, grass silage and concentrate were fed in a 40 : 30 : 30 ratio on DM basis. Rumen fluid was collected from each cow at days −4, 1, 4, 8, 15 and 22 relative to the introduction of the additives in the diets. On each of these days, a 48-h GP experiment was performed in which rumen fluid from each individual donor cow was incubated with each of the three substrates that reflected the treatment diets offered to the cows. DM intake was on average 19.8, 20.1 and 16.2 kg/day with an average fat- and protein-corrected milk production of 30.7, 31.7 and 26.2 kg/day with diet CON, AR and LA, respectively. In general, feed additives in the donor cow diet had a larger effect on gas and CH4 production than the same additives in the incubation substrate. Incubation substrate affected asymptotic GP, half-time of asymptotic CH4 production, total volatile fatty acid (VFA) concentration, molar proportions of propionate and butyrate and degradation of organic matter (OMD), but did not affect CH4 production. No substrate×day interactions were observed. A significant diet×day interaction was observed for in vitro gas and CH4 production, total VFA concentration, molar proportions of VFA and OMD. From day 4 onwards, the LA diet persistently reduced gas and CH4 production, total VFA concentration, acetate molar proportion and OMD, and increased propionate molar proportion. In vitro CH4 production was reduced by the AR diet on day 8, but not on days 15 and 22. In line with these findings, the molar proportion of propionate in fermentation fluid was greater, and that of acetate smaller, for the AR diet than for the CON diet on day 8, but not on days 15 and 22. Overall, the data indicate a short-term effect of AR on CH4 production, whereas the CH4-mitigating effect of LA persisted.
    A straightforward method to determine flavouring substances in food by GC-MS
    Lopez Sanchez, P. ; Sisseren, M. van; Marco, S. De; Jekel, A.A. ; Nijs, W.C.M. de; Mol, J.G.J. - \ 2015
    Food Chemistry 174 (2015). - ISSN 0308-8146 - p. 407 - 416.
    solid-phase extraction - essential oils - cinnamaldehyde - beverages - coumarin - cinnamon - products - pulegone - absinthe - thujone
    A straightforward GC–MS method was developed to determine the occurrence of fourteen flavouring compounds in food. It was successfully validated for four generic types of food (liquids, semi-solids, dry solids and fatty solids) in terms of limit of quantification, linearity, selectivity, matrix effects, recovery (53–120%) and repeatability (3–22%). The method was applied to a survey of 61 Dutch food products. The survey was designed to cover all the food commodities for which the EU Regulation 1334/2008 set maximum permitted levels. All samples were compliant with EU legislation. However, the levels of coumarin (0.6–63 mg/kg) may result in an exposure that, in case of children, would exceed the tolerable daily intake (TDI) of 0.1 mg/kg bw/day. In addition to coumarin, estragole, methyl-eugenol, (R)-(+)-pulegone and thujone were EU-regulated substances detected in thirty-one of the products. The non-EU regulated alkenylbenzenes, trans-anethole and myristicin, were commonly present in beverages and in herbs-containing products.
    Chemical analysis of estragole in fennel based teas and associated safety assessment using the Margin of Exposure (MOE) approach
    Berg, S.J.P.L. van den; Alhusainy, W. ; Restani, P. ; Rietjens, I. - \ 2014
    Food and Chemical Toxicology 65 (2014). - ISSN 0278-6915 - p. 147 - 154.
    foeniculum-vulgare - essential oils - methyl eugenol - supplements - fruits - risk
    This study describes the analysis of estragole in dry fennel preparations and in infusions prepared from them and an associated safety assessment. A wide range of estragole levels of 0.15–13.3 mg/g dry fennel preparation was found. The estragole content in infusions was considerably lower ranging between 0.4 and 133.4 µg/25 mL infusion prepared from 1 g dry material. Infusions prepared from whole fennel fruits contained about 3-fold less estragole compared to infusions prepared from fine cut fennel material. Safety assessment was performed using the Margin of Exposure (MOE) approach comparing available tumour data to the estimated daily estragole intakes from the consumption of 1–3 cups fennel tea. MOEs obtained for adults generally point at a low priority for risk management, especially when one cup of fennel tea is used daily during lifetime. MOEs for use of fennel teas by children were generally
    Effect of antimicrobial compounds on cut Gerbera flowers: Poor relation between stem bending and numbers of bacteria in the vase water
    Witte, Y. van de; Harkema, H. ; Doorn, W.G. van - \ 2014
    Postharvest Biology and Technology 91 (2014). - ISSN 0925-5214 - p. 78 - 83.
    jamesonii flowers - essential oils - rose flowers - membranes - longevity - stress - sugars - plants - life - acid
    Gerbera flowers (Gerbera jamesonii) often show stem bending. In four cultivars (Tamara, Liesbeth, Cora, and Mickey), we tested the effects on bending of antimicrobial compounds (chlorine bleach, a slow release chlorine compound, 8-hydroxyquinoline citrate [HQC], silver nitrate, carvacrol and thymol), some combined with sugars. At concentrations used for other cut flowers, inclusion in the vase solution of several of the antimicrobial compounds delayed bending, had no effect, or hastened bending. Hastening of bending was found at higher concentrations. It was accompanied with visible damage on the stem ends. Results with HQC indicated high toxicity as it did not delay bending at any of the concentration tested (100-400 mg L-1). At 200 mg L-1 HQC induced growth of bacteria that were not found in the controls. The number of bacteria in the vase water showed a low correlation with bending. Visible toxicity on the stem surface was often associated with a high bacteria count. However, at relatively high concentrations of the antimicrobial compounds stem bending was associated with a low count. This indicated an effect other than bacteria. Water uptake was low in stems that bent early. It is hypothesized that material from dead stem cells resulted in a xylem blockage which led to early bending. Sucrose at 15 g L-1 in combination with an antimicrobial compound (slow release chlorine, HQC) resulted in the absence of stem damage and produced much less bending than the same concentration of the antimicrobial compounds alone. Sucrose apparently counteracted the toxic effects of the antimicrobial chemicals. (C) 2014 Published by Elsevier B.V.
    Testen van stoffen met een mogelijk afwerende werking op trips
    Pijnakker, J. ; Leman, A. - \ 2014
    Bleiswijk : Wageningen UR Glastuinbouw (Rapport / Wageningen UR Glastuinbouw 1325) - 22
    frankliniella occidentalis - plantenplagen - waardplanten - etherische oliën - insectenplagen - lokstoffen - vangmethoden - proeven - frankliniella occidentalis - plant pests - host plants - essential oils - insect pests - attractants - trapping - trials
    Secundaire plantenstoffen, zoals essentiële oliën, hebben het vermogen om te interfereren met het selectieproces van een geschikte waardplant door een plaaginsect. In het eerste gedeelte van dit verslag worden de resultaten beschreven van laboratorium- en kasproeven waarin een aantal mogelijk afwerende plantenstoffen zijn getest tegen Californische trips (Frankliniella occidentalis). In het tweede gedeelte van dit verslag is aandacht besteed aan de extrinsieke en intrinsieke factoren die de werking van de commercieel verkrijgbare lokstof Lurem-TR op Californische trips kunnen beïnvloeden
    Evaluation of tobacco (Nicotiana tabacum L. cv. Petit Havana SR1) hairy roots for the production of geraniol, the first committed step in terpenoid indole alkaloid pathway
    Ritala, A. ; Dong, L. ; Imseng, N. ; Seppanen-Laakso, T. ; Vasilev, N. ; Krol, A.R. van der; Rischer, H. ; Maaheimo, H. ; Virkki, A. ; Brandli, J. ; Schillberg, S. ; Eibl, R. ; Bouwmeester, H.J. ; Oksman-Caldentey, K.M. - \ 2014
    Journal of Biotechnology 176 (2014). - ISSN 0168-1656 - p. 20 - 28.
    catharanthus-roseus - isoprenoid biosynthesis - plastidial pathways - essential oils - key enzyme - monoterpene - cultures - synthase - cells - bioreactors
    The terpenoid indole alkaloids are one of the major classes of plant-derived natural products and are well known for their many applications in the pharmaceutical, fragrance and cosmetics industries. Hairy root cultures are useful for the production of plant secondary metabolites because of their genetic and biochemical stability and their rapid growth in hormone-free media. Tobacco (Nicotiana tabacum L. cv. Petit Havana SR1) hairy roots, which do not produce geraniol naturally, were engineered to express a plastidtargeted geraniol synthase gene originally isolated from Valeriana officinalis L. (VoGES). A SPME-GC–MS screening tool was developed for the rapid evaluation of production clones. The GC–MS analysis revealed that the free geraniol content in 20 hairy root clones expressing VoGES was an average of 13.7 g/g dry weight (DW) and a maximum of 31.3 g/g DW. More detailed metabolic analysis revealed that geraniol derivatives were present in six major glycoside forms, namely the hexose and/or pentose conjugates of geraniol and hydroxygeraniol, resulting in total geraniol levels of up to 204.3 g/g DW following deglycosylation. A benchtop-scale process was developed in a 20-L wave-mixed bioreactor eventually yielding hundreds of grams of biomass and milligram quantities of geraniol per cultivation bag.
    Comparison of plant-based expression platforms for the heterologous production of geraniol
    Vasilev, N. ; Schmitz, C. ; Dong, L. ; Ritala, A. ; Imseng, N. ; Hakkinen, S.T. ; Krol, A.R. van der; Eibl, R. ; Oksman-Caldentey, K.M. ; Bouwmeester, H.J. ; Fischer, R. ; Schillberg, S. - \ 2014
    Plant Cell, Tissue and Organ Culture: an international journal on in vitro culture of higher plants 117 (2014)3. - ISSN 0167-6857 - p. 373 - 380.
    mevalonate kinase-deficiency - pelargonium-graveolens - chemical-composition - catharanthus-roseus - response factor - mentha-spicata - essential oils - sweet basil - mouse model - biosynthesis
    We compared the ability of different plant-based expression platforms to produce geraniol, a key metabolite in the monoterpenoid branch of the terpenoid indole alkaloid biosynthesis pathway. A geraniol synthase gene isolated from Valeriana officinalis (VoGES) was stably expressed in different tobacco systems. Intact plants were grown in vitro and in the greenhouse and were used to generate cell suspension and hairy root cultures. VoGES was also transiently expressed in N. benthamiana. The highest geraniol content was produced by intact transgenic plants grown in vitro (48 µg/g fresh weight, fw), followed by the transient expression system (27 µg/g fw), transgenic plants under hydroponic conditions in the greenhouse and cell suspension cultures (16 µg/g fw), and finally hairy root cultures (9 µg/g fw). Differences in biomass production and the duration of cultivation resulted in a spectrum of geraniol productivities. Cell suspension cultures achieved a geraniol production rate of 1.8 µg/g fresh biomass per day, whereas transient expression produced 5.9 µg/g fresh biomass per day (if cultivation prior to agroinfiltration is ignored) or 0.5 µg/g fresh biomass per day (if cultivation prior to agroinfiltration is included). The superior productivity, strict process control and simple handling procedures available for transgenic cell suspension cultures suggest that cells are the most promising system for further optimization and ultimately for the scaled-up production of geraniol
    Capturing flavors from Capsicum baccatum by introgression in sweet pepper
    Eggink, P.M. ; Tikunov, Y.M. ; Maliepaard, C.A. ; Haanstra, J.P.W. ; Rooij, H. de; Vogelaar, A. ; Gutteling, E.W. ; Freymark, G. ; Bovy, A.G. ; Visser, R.G.F. - \ 2014
    Theoretical and Applied Genetics 127 (2014)2. - ISSN 0040-5752 - p. 373 - 390.
    plastid compartment size - lycopersicon-esculentum - volatile compounds - anthracnose resistance - chemical-composition - gas-chromatography - sensory evaluation - mass-spectrometry - candidate gene - essential oils
    The species Capsicum baccatum includes the most common hot peppers of the Andean cuisine, known for their rich variation in flavors and aromas. So far the C. baccatum genetic variation remained merely concealed for Capsicum annuum breeding, due to post-fertilization genetic barriers encountered in interspecific hybridization. However, to exploit the potential flavor wealth of C. baccatum we combined interspecific crossing with embryo rescue, resulting in a multi-parent BC2S1 population. Volatile and non-volatile compounds plus some physical characters were measured in mature fruits, in combination with taste evaluation by a sensory panel. An enormous variation in biochemical composition and sensory attributes was found, with almost all traits showing transgression. A population-specific genetic linkage map was developed for QTL mapping. BC2S1 QTLs were validated in an experiment with near-isogenic lines, resulting in confirmed genetic effects for physical, biochemical and sensory traits. Three findings are described in more detail: (1) A small C. baccatum LG3 introgression caused an extraordinary effect on flavor, resulting in significantly higher scores for the attributes aroma, flowers, spices, celery and chives. In an attempt to identify the responsible biochemical compounds few consistently up- and down-regulated metabolites were detected. (2) Two introgressions (LG10.1 and LG1) had major effects on terpenoid content of mature fruits, affecting at least 15 different monoterpenes. (3) A second LG3 fragment resulted in a strong increase in Brix without negative effects on fruit size. The mapping strategy, the potential application of studied traits and perspectives for breeding are discussed.
    Four new depsides in Origanum dictamnus methanol extract
    Exarchou, V. ; Takis, P.G. ; Malouta, M. ; Vervoort, J. ; Karali, E. ; Troganis, A.N. - \ 2013
    Phytochemistry Letters 6 (2013)1. - ISSN 1874-3900 - p. 46 - 52.
    greek aromatic plants - antioxidant activities - salvia-officinalis - acid-derivatives - essential oils - caffeic acid - antimicrobial activity - constituents - l. - lamiaceae
    We herein describe the identification of four new depsides present in methanol extract of Origanum dictamnus. O. dictamnus’ (dittany) aerial parts methanol extract was subjected to semi-preparative RP-HPLC fractionation followed by identification of individual compounds in each fraction using 1D/2D NMR, MS approaches and DFT calculations. The structural data revealed that 4 of the compounds were novel hitherto unidentified molecules, whereas the other 6 corresponded to known structures belonging to the groups of monoterpenes, phenolic acids and depsides. We have additionally estimated the antioxidant capacity of the methanol extract and individual fractions using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) in vitro assay. Methanol extract exhibited significant scavenging activity, which was attributed predominantly to the depside group of phytochemicals. The scavenging activity of the new compounds is reported herein for first time. Moreover, the antimitotic activities of the methanol extract as well as that of rosmarinic acid were examined and appeared to be several fold weaker comparing to their scavenging capacity.
    Characterization of two geraniol synthases from Valeriana officinalis and Lippia dulcis: similar activity but difference in subcellular localization
    Dong, L. ; Miettinen, K. ; Verstappen, F.W.A. ; Voster, A. ; Jongsma, M.A. ; Memelink, J. ; Krol, S. van der; Bouwmeester, H.J. - \ 2013
    Metabolic Engineering 20 (2013). - ISSN 1096-7176 - p. 198 - 211.
    indole alkaloid pathway - gland secretory-cells - roseus hairy roots - catharanthus-roseus - monoterpene biosynthesis - isoprenoid biosynthesis - plant transformation - essential oils - grape juice - metabolism
    Two geraniol synthases (GES), from Valeriana officinalis (VoGES) and Lippia dulcis (LdGES), were isolated and were shown to have geraniol biosynthetic activity with Km values of 32 µM and 51 µM for GPP, respectively, upon expression in Escherichia coli. The in planta enzymatic activity and sub-cellular localization of VoGES and LdGES were characterized in stable transformed tobacco and using transient expression in Nicotiana benthamiana. Transgenic tobacco expressing VoGES or LdGES accumulate geraniol, oxidized geraniol compounds like geranial, geranic acid and hexose conjugates of these compounds to similar levels. Geraniol emission of leaves was lower than that of flowers, which could be related to higher levels of competing geraniol-conjugating activities in leaves. GFP-fusions of the two GES proteins show that VoGES resides (as expected) predominantly in the plastids, while LdGES import into to the plastid is clearly impaired compared to that of VoGES, resulting in both cytosolic and plastidic localization. Geraniol production by VoGES and LdGES in N. benthamiana was nonetheless very similar. Expression of a truncated version of VoGES or LdGES (cytosolic targeting) resulted in the accumulation of 30% less geraniol glycosides than with the plastid targeted VoGES and LdGES, suggesting that the substrate geranyl diphosphate is readily available, both in the plastids as well as in the cytosol. The potential role of GES in the engineering of the TIA pathway in heterologous hosts is discussed.
    The methanolic extract of Cordycepts militaris (L.) Link fruiting body shows antioxidant, antibacterial, antifungal and antihuman tumor cell lines properties
    Reis, F.S. ; Barros, L. ; Calhelha, R.C. ; Ciric, A. ; Griensven, L.J.L.D. van; Sokovic, M. ; Ferreira, I.C.F.R. - \ 2013
    Food and Chemical Toxicology 62 (2013). - ISSN 0278-6915 - p. 91 - 98.
    appreciated cultivated mushrooms - photodiode-array detection - essential oils - vapor-phase - liquid-chromatography - edible mushrooms - wild mushrooms - fungi - susceptibility - bodies
    Being Cordyceps militaris (L.) Link recognized as a medicinal and edible mushroom, this work intends to reveal new interesting bioactive molecules that could be isolated from this species. Hydrophilic and lipophilic compounds were analyzed by chromatographic techniques coupled to different detectors. The methanolic extract of C. militaris was tested for its antioxidant, antibacterial, antifungal and anti-proliferative properties in different human tumor cell lines. Mannitol (2.01g/100gdw) and trehalose (24.71g/100g) were the free sugars found in C. militaris. Polyunsaturated fatty acids (68.87%) predominated over saturated fatty acids (23.40%) and d-tocopherol was the only isoform of vitamin E detected (55.86µg/100g). The organic acids found in this mushroom were oxalic, citric and fumaric acids (0.33, 7.97 and 0.13g/100g, respectively). p-Hydroxybenzoic acid was the only phenolic acid quantified in this species (0.02mg/100g); although cinnamic acid was also found (0.11mg/100g). The methanolic extract of C. militaris proved to inhibit lipid peroxidation, have reducing power and scavenge free radicals. This extract also revealed strong antibacterial and antifungal properties. Finally, the C. militaris extract was able to inhibit the proliferation of MCF-7 (breast), NCI-H460 (non-small lung), HCT-15 (colon) and HeLa (cervical) human carcinoma cell lines.
    Relation between HLA genes, human skin volatiles and attractiveness of humans to malaria mosquitoes
    Verhulst, N.O. ; Beijleveld, H. ; Qiu, Y.T. ; Maliepaard, C.A. ; Verduyn, W. ; Haasnoot, G.W. ; Claas, F.H.J. ; Mumm, R. ; Bouwmeester, H.J. ; Takken, W. ; Loon, J.J.A. van; Smallegange, R.C. - \ 2013
    Infection, Genetics and Evolution 18 (2013). - ISSN 1567-1348 - p. 87 - 93.
    major histocompatibility complex - gambiae-sensu-stricto - human axillary odor - anopheles-gambiae - aedes-aegypti - mating preferences - carbon dioxide - essential oils - host-seeking - body odors
    Chemical cues are considered to be the most important cues for mosquitoes to find their hosts and humans can be ranked for attractiveness to mosquitoes based on the chemical cues they emit. Human leukocyte antigen (HLA) genes are considered to be involved in the regulation of human body odor and may therefore affect human attractiveness to mosquitoes, and hence, affect the force of malaria transmission. In the present study the correlations between HLA profiles, human skin volatiles and human attractiveness to the malaria mosquito Anopheles gambiae Giles sensu stricto were examined. Skin emanations of 48 volunteers were collected by rubbing a foot over glass beads. Previously the attractiveness of these emanations to An. gambiae was determined. In this study, the chemical composition of these emanations was determined by gas chromatography–mass spectroscopy (GC–MS) and blood samples of all volunteers were taken for HLA analysis. Hierarchical cluster analysis (HCA), partial least squares discriminant analysis (PLS-DA), Fisher’s exact test and random forest regression were used to test for correlations between individuals classified as either highly or poorly attractive to mosquitoes and their HLA profile and volatile composition. HLA profiling suggests that people carrying HLA gene Cw*07 are more attractive to mosquitoes. GC–MS revealed that limonene, 2-phenylethanol and 2-ethyl-1-hexanol were associated with individuals that were poorly attractive to An.gambiae and lactic acid, 2-methylbutanoic acid, tetradecanoic acid and octanal with individuals that were highly attractive. Such compounds offer potential for disruption of mosquito behavior in malaria intervention programs.
    Dietary inclusion of diallyl disulfide, yucca powder, calcium fumarate, an extruded linseed product, or medium-chain fatty acids does not affect methane production in lactating dairy cows
    Zijderveld, S.M. van; Dijkstra, J. ; Perdok, H.B. ; Newbold, J.R. ; Gerrits, W.J.J. - \ 2011
    Journal of Dairy Science 94 (2011)6. - ISSN 0022-0302 - p. 3094 - 3104.
    production in-vitro - rumen microbial fermentation - ruminal fermentation - linolenic acids - essential oils - beef-cattle - garlic oil - metaanalysis - metabolism - schidigera
    Two similar experiments were conducted to assess the effect of diallyl disulfide (DADS), yucca powder (YP), calcium fumarate (CAFU), an extruded linseed product (UNSAT), or a mixture of capric and caprylic acid (MCFA) on methane production, energy balance, and dairy cow performance. In experiment 1, a control diet (CON1) and diets supplemented with 56 mg of DADS/kg of dry matter (DM), 3g of YP/kg of DM, or 25 g of CAFU/kg of DM were evaluated. In experiment 2, an inert saturated fat source in the control diet (CON2) was exchanged isolipidically for an extruded linseed source (100g/kg of DM; UNSAT) or a mixture of C8:0 and C10:0 (MCFA; 20.3g/kg of DM). In experiment 2, a higher inclusion level of DADS (200mg/kg of DM) was also tested. Both experiments were conducted using 40 lactating Holstein-Friesian dairy cows. Cows were adapted to the diet for 12 d and were subsequently kept in respiration chambers for 5 d to evaluate methane production, diet digestibility, energy balance, and animal performance. Feed intake was restricted to avoid confounding effects of possible differences in ad libitum feed intake on methane production. Feed intake was, on average, 17.5 and 16.6 kg of DM/d in experiments 1 and 2, respectively. None of the additives reduced methane production in vivo. Methane production in experiment 1 was 450, 453, 446, and 423 g/d for CON1 and the diets supplemented with DADS, YP, and CAFU, respectively. In experiment 2, methane production was 371, 394, 388, and 386 g/d for CON2 and the diets supplemented with UNSAT, MCFA, and DADS, respectively. No effects of the additives on energy balance or neutral detergent fiber digestibility were observed. The addition of MCFA increased milk fat content (5.38% vs. 4.82% for control) and fat digestibility (78.5% vs. 59.8% for control), but did not affect milk yield or other milk components. The other products did not affect milk yield or composition. Results from these experiments emphasize the need to confirm methane reductions observed in vitro with in vivo data.
    A novel method to determine simultaneously methane production during in vitro gas production using fully automated equipment
    Pellikaan, W.F. ; Hendriks, W.H. ; Uwimanaa, G. ; Bongers, L.J.G.M. ; Becker, P.M. ; Cone, J.W. - \ 2011
    Animal Feed Science and Technology 168 (2011)3-4. - ISSN 0377-8401 - p. 196 - 205.
    rumen microbial fermentation - essential oils - production profiles - condensed tannins - ruminant feeds - dairy-cows - kinetics - nitrogen - nutrition - invitro
    An adaptation of fully automated gas production equipment was tested for its ability to simultaneously measure methane and total gas. The simultaneous measurement of gas production and gas composition was not possible using fully automated equipment, as the bottles should be kept closed during the incubations. A separate small opening with a screw cap and septum was made in each bottle, making it possible to take very small aliquots (10 µl) from the gas in the headspace with a syringe for immediate gas analysis. As the used automatic gas production equipment was a venting system, corrections had to be made for the vented total gas and methane, as well as for the dilution of the produced methane with the gas in the headspace. To test the suitability and accuracy of the system, known amounts of methane were injected in bottles in the venting system and methane concentrations in the headspace were determined. It proved that the methane concentration in the headspace, corrected for the vented gas, coincided with the injected amount of methane. To show the potency of the adapted equipment, experiments were conducted with different feedstuffs. Total gas production and methane production were recorded and their relationships were calculated. The ability of the system to test feed additives for methane reduction was demonstrated for maize and soybean hulls as substrate (0.5 g DM), supplemented with monensin (15 mg), sodium-2-bromoethanesulphonate (BES, 15 mg), cinnemaldehyde (150 mg) and tea tannins (150 mg), additives known to effect methane synthesis. The adapted gas production equipment showed to be a powerful tool to determine rate and extent of gas production as a measure of fermentation and to simultaneously determine methane production.
    Metabolic engineering of geranic acid in maize to achieve fungal resistance is compromised by novel glycosylation patterns
    Yang, T. ; Stoopen, G. ; Yalpani, N. ; Vervoort, J.J.M. ; Vos, R. de; Voster, A. ; Verstappen, F.W.A. ; Bouwmeester, H.J. ; Jongsma, M.A. - \ 2011
    Metabolic Engineering 13 (2011)4. - ISSN 1096-7176 - p. 414 - 425.
    altered monoterpene composition - seed-borne fungi - essential oils - fusarium-graminearum - terpenoid metabolism - linalool synthase - limonene synthase - mass-spectrometry - beta-glucosidase - tomato fruits
    Many terpenoids are known to have antifungal properties and overexpression of these compounds in crops is a potential tool in disease control. In this study, 15 different mono- and sesquiterpenoids were tested in vitro against two major pathogenic fungi of maize (Zea mays), Colletotrichum graminicola and Fusarium graminearum. Among all tested terpenoids, geranic acid showed very strong inhibitory activity against both fungi (MIC
    Control methods for Dermanyssus gallinae in systems for laying hens: results of an international seminar
    Mul, M.F. ; Niekerk, T.G.C.M. van; Chirico, J. ; Maurer, V. ; Kilpinen, O. ; Sparagano, O. ; Thind, B. ; Zoons, J. ; Moore, D. ; Bell, B. ; Gjevre, A.G. ; Chauve, C. - \ 2009
    Worlds Poultry Science Journal 65 (2009)4. - ISSN 0043-9339 - p. 589 - 599.
    poultry red mite - essential oils - chicken mite - acari - host - susceptibility - temperature - candidate - humidity - traps
    This paper reports the results of a seminar on poultry red mite (PRM), Dermanyssus gallinae. Eighteen researchers from eight European countries discussed life cycle issues of the mite, effects of mites on hens and egg production, and monitoring and control methods for PRM in poultry facilities. It was determined that PRM probably causes more damage than envisaged, with the cost in The Netherlands alone reaching 11 million euro per annum. However a great deal is still unknown about PRM (e.g. reproduction, survival methods, etc.) and that PRM monitoring is an important instrument in recognising and admitting the problem and in taking timely measures. Currently, the most promising control method combines heating the hen house in combination with chemical treatments. Future areas of development which show promise include the use of entomopathogenic fungi, vaccination and predatory mites. The final aim is to solve the problem of D. gallinae in housing systems for laying hens.
    Impact of bioactive substances on the gastrointestinal tract and performance of weaned piglets: a review
    Lalles, J.P. ; Bosi, P. ; Janczyk, P. ; Koopmans, S.J. ; Torrallardona, D. - \ 2009
    Animal 3 (2009)12. - ISSN 1751-7311 - p. 1625 - 1643.
    dried animal plasma - enterotoxigenic escherichia-coli - in-feed antibiotics - gut-derived sepsis - low-threonine diet - egg-yolk antibody - essential oils - antimicrobial activity - growth-performance - organic-acids
    The EU ban on in-feed antibiotics has stimulated research on weaning diets as a way of reducing post-weaning gut disorders and growth check in pigs. Many bioactive components have been investigated but only few have shown to be effective. Amongst these, organic acids (OA) have been shown to exert a bactericidal action mediated by non-dissociated OA, by lowering gastric pH, increasing gut and pancreas enzyme secretion and improving gut wall morphology. It has been postulated that they may also enhance non-specific immune responses and improve disease resistance. In contrast, relatively little attention has been paid to the impact of OA on the stomach but recent data show they can differently affect gastric histology, acid secretion and gastric emptying. Butyrate and precursors of butyric acid have received special attention and although promising results have been obtained, their effects are dependent upon the dose, treatment duration, initial age of piglets, gastrointestinal site and other factors. The amino acids (AA) like glutamine, tryptophan and arginine are supportive in improving digestion, absorption and retention of nutrients by affecting tissue anabolism, stress and (or) immunity. Glutamine, cysteine and threonine are important for maintaining mucin and permeability of intestinal barrier function. Spray-dried plasma (SDP) positively affects gut morphology, inflammation and reduces acquired specific immune responses via specific and a-specific influences of immunoglobulins and other bioactive components. Effects are more pronounced in early-weaned piglets and under poorer health conditions. Little interaction between plasma protein and antibiotics has been found, suggesting distinct modes of action and additive effects. Bovine colostrum may act more or less similarly to SDP The composition of essential oils is highly variable, depending on environmental and climatic conditions and distillation methods. These oils differ widely in their antimicrobial activity in vitro and some components of weaning diets may decrease their activity Results in young pigs are highly variable depending upon the product and doses used. These studies suggest that relatively high concentrations of essential oils are needed for beneficial effects to be observed and it has been assumed that these plant extracts mimic most of the effects of antibiotics active on gut physiology, microbiology and immunology. Often, bioactive substances protective to the gut also stimulate feed intake and growth performance. New insights on the effects of selected OA and AA, protein sources (especially SDP bovine colostrum) and plant extracts with anti-bacterial activities on the gut are reported in this review.
    Physiologically based biokinetic (PBBK) models to characterize dose dependent effects, species differences, and interindividual human variation and detoxification of estragole
    Punt, A. - \ 2009
    Wageningen University. Promotor(en): Ivonne Rietjens; Peter van Bladeren, co-promotor(en): B. Schilter. - [S.l.] : s.n. - ISBN 9789085853718 - 251
    toxiciteit - soortverschillen - metabolische detoxificatie - etherische oliën - risicoschatting - carcinogenese - toxicity - species differences - metabolic detoxification - essential oils - risk assessment - carcinogenesis - cum laude
    cum laude graduation (with distinction)
    Evaluation of two counterflow traps for testing behaviour-mediating compounds for the malaria vector Anopheles gambiae s.s. under semi-field conditions in Tanzania
    Schmied, W.H. ; Takken, W. ; Killeen, G.F. ; Knols, B.G.J. ; Smallegange, R.C. - \ 2008
    Malaria Journal 7 (2008). - ISSN 1475-2875 - 9 p.
    adult aedes-aegypti - human landing catch - mm-x traps - western kenya - field-evaluation - carbon-dioxide - essential oils - bg-sentinel - light trap - insect repellents
    Background Evaluation of mosquito responses towards different trap-bait combinations in field trials is a time-consuming process that can be shortened by experiments in contained semi-field systems. Possible use of the BG Sentinel (BGS) trap to sample Anopheles gambiae s.s. was evaluated. The efficiency of this trap was compared with that of the Mosquito Magnet-X (MM-X) trap, when baited with foot odour alone or combinations of foot odour with carbon dioxide (CO2) or lemongrass as behaviour-modifying cues. Methods Female An. gambiae s.s. were released in an experimental flight arena that was placed in a semi-field system and left overnight. Catch rates for the MM-X and BGS traps were recorded. Data were analysed by fitting a generalized linear model to the (n+1) transformed catches. Results Both types of traps successfully captured mosquitoes with all odour cues used. When the BGS trap was tested against the MM-X trap in a choice assay with foot odour as bait, the BGS trap caught about three times as many mosquitoes as the MM-X trap (P = 0.002). Adding CO2 (500 ml/min) to foot odour increased the number of mosquitoes caught by 268% for the MM-X (P <0.001) and 34% (P = 0.051) for the BGS trap, compared to foot odour alone. When lemongrass leaves were added to foot odour, mosquito catches were reduced by 39% (BGS, P <0.001) and 38% (MM-X, P = 0.353), respectively. Conclusion The BGS trap shows high potential for field trials due to its simple construction and high catch rate when baited with human foot odour only. However, for rapid screening of different baits in a contained semi-field system, the superior discriminatory power of the MM-X trap is advantageous.
    Proceedings of the 2nd international symposium on natural preservatives in food, feed, and cosmetics : Amsterdam, the Netherlands, June 7-8, 2006
    Havkin-Frenkel, D. ; Dudai, N. ; Mheen, H.J.C.J. van der - \ 2008
    Leuven : International Society for Horticultural Science (Acta horticulturae 778) - ISBN 9789066057302 - 110
    conserveermiddelen - voedselconserveermiddelen - voer - cosmetica - natuurlijke producten - medicinale planten - antioxidanten - etherische oliën - aromatische gewassen - preservatives - food preservatives - feeds - cosmetics - natural products - medicinal plants - antioxidants - essential oils - aromatic plants
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