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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Het effect van temperatuur op de bloem aanleg en het doorbreken van de winterrust in tulp
Leeggangers, H.A.C.F. ; Hilhorst, H.W.M. ; Immink, G.H. - \ 2014
bloembollen - tulpen - verdroging - bloembeginsels - cultuurmethoden - proeven - temperatuur - kou - winter - groeistadia - ornamental bulbs - tulips - desiccation - flower primordia - cultural methods - trials - temperature - cold - growth stages
Temperatuur is een van de belangrijkste factoren die de ontwikkeling van tulpen beïnvloedt. Het warme voorjaar in 2008 leidde tot bloemverdroging in Strong Gold en in 2011 werd hetzelfde aangetroffen bij partijen van o.a. Yokohama, Purple Prince en Escape (Figuur 1). Niet alleen een warm voorjaar kan een probleem geven, maar ook een warme winter gevolgd door een koud voorjaar (2012). Hierdoor staan de tulpen laat in bloei gevolgd door een vertraagde aanleg van de bloem knop. Voortijdig rooijen kan de aanleg van de bloem knop beïnvloeden. Doel van dit onderzoek is om het effect van temperatuur op de bloem aanleg te bestuderen en de invloed van kou op de ontwikkeling binnen in de bol tijdens de winterrust.
Warmtepomp verplaatst warmte en kou naar behoefte
Animal Sciences Group (ASG), - \ 2011
Lelystad : Animal Sciences Group, Business Unit Veehouderij
varkenshouderij - varkensstallen - energiebesparing - warmte - kou - warmtepompen - elektriciteit - koelen - verwarming - pig farming - pig housing - energy saving - heat - cold - heat pumps - electricity - cooling - heating
Een warmtepomp is geschikt om warmte of kou van de ene naar de andere plaats te brengen, waarbij de warmtepomp 'laagwaardige' warmte omzet in 'hoogwaardige' warmte. Hiermee is flink op energie te besparen. Wel is er elektriciteit nodig om de pomp te laten draaien. Rendabel benutten van een warmtepomp vergt een gerichte inzet.
Shrubs in the cold : interactions between vegetation, permafrost and climate in Siberian tundra
Blok, D. - \ 2011
University. Promotor(en): Frank Berendse, co-promotor(en): Monique Heijmans; Gabriela Schaepman. - [S.l.] : S.n. - ISBN 9789461730251 - 152
struiken - vegetatie - permafrost - kou - klimaat - interacties - toendra - arctische ecologie - plantenecologie - siberië - shrubs - vegetation - cold - climate - interactions - tundra - arctic ecology - plant ecology - siberia

The Arctic is experiencing strong increases in air temperature during the last decades. High-latitude tundra regions are very responsive to changes in temperature and may cause a shift in tundra vegetation composition towards greater dominance of deciduous shrubs. With increasing deciduous shrub cover, the surface albedo (proportion of sunlight that is reflected to the atmosphere) may be reduced and lead to air warming by trapping more solar radiation into the Arctic ecosystem. As a result of this warming, thawing of carbon-rich permafrost soils may increase and cause a large greenhouse gas flux to the atmosphere, thus contributing to global warming.

In my thesis I studied how climate influences shrub growth in the Siberian tundra and how climate-induced changes in shrub cover affect summer permafrost thaw and surface albedo. I investigated these interactions between climate, permafrost and Arctic shrub growth using a combination of shrub ring width analysis, field experiments and remote sensing techniques. I measured and compared growth ring widths with meteorological station data and observed that shrub growth is stimulated by higher summer air temperatures. By performing a shrub removal experiment, I demonstrated that a temperature-induced increase in shrub cover may reduce summer permafrost thaw. Shading by the shrub canopy reduced the transfer of energy to the soil. A denser shrub cover thus effectively reduces summer permafrost thaw, despite leading at the same time to a lower surface albedo. These results indicate it is important to incorporate feedbacks between shrub growth, climate and permafrost thaw in model predictions on the Arctic climate and stability of permafrost in a future warmer world.

Meer winterschade: De Amerikaanse ribkwal is verdwenen
Bragt, P.H. van - \ 2010
Nature Today 2010 (2010)09-07.
geïntroduceerde soorten - invasies - kwal (weekdier) - kustwateren - kou - introduced species - invasions - jellyfish - coastal water - cold
Sinds 2006 is de Amerikaanse ribkwal een exotische gast in onze zoute wateren. Hij vestigde zich meteen explosief langs de hele Nederlandse kust en ook elders op onder andere de Duitse, Deense en Zuid-Noorse kust en de Baltische Zee. Vooral in de Oosterschelde en Grevelingen kwam hij in 2007 en 2008 in onmeetbare hoeveelheden voor. Zoveel zelfs dat men vreesde dat deze nieuwe wereldburger van onze faunalijst een ecologische ramp zou gaan veroorzaken. Vorig jaar was er al sprake van een relatieve daling van het aantal ribkwallen in onze kustwateren. Nu lijken ze zowel uit de Zeeuwse Delta als in de Waddenzee zijn verdwenen. Het is aannemelijk dat de twee recente strenge winters en dan vooral de langdurige winter van 2009-2010 de Amerikaanse ribkwal uit onze kustwateren heeft verdreven.
Eikenprocessierups doorstaat koude winter goed
Mulder, S. - \ 2010
Nature Today 2010 (2010)19-02-2010.
thaumetopoea processionea - overwintering - bosplagen - kou - plantenplagen - rupsen - forest pests - cold - plant pests - caterpillars
Eikenprocessierupsen zijn niet gedeerd door de langdurige koude van deze winter. Bij het opensnijden van eipakketjes blijken de rupsjes springlevend naar buiten te komen. Het is nog te vroeg om nu al iets te zeggen over de mogelijke overlast later dit jaar. Dat is afhankelijk van de weersomstandigheden in april, wanneer de rupsen normaalgesproken uit hun ei komen.
Teeltadviezen DIF en kouval voor pot- en perkplanten : 15 jaar onderzoek op een rij gezet
Dijkshoorn-Dekker, M.W.C. - \ 2000
Aalsmeer : Proefstation voor Bloemisterij en Glasgroente, Vestiging Aalsmeer (Rapport / Proefstation voor Bloemisterij en Glasgroente 242) - 21
potplanten - sierplanten - temperatuur - kou - containerplanten - tuinplanten - pot plants - ornamental plants - temperature - cold - container grown plants - bedding plants
Vermindering ongelijke bloei bij vroege trek van azalea door koudebehandeling
Kromwijk, A. - \ 2000
Aalsmeer : Proefstation voor Bloemisterij en Glasgroente, Vestiging Aalsmeer (Rapport / Proefstation voor Bloemisterij en Glasgroente 197) - 23
rhododendron - temperatuur - kou - bloeidatum - vroegheid - bloemen - sierplanten - temperature - cold - flowering date - earliness - flowers - ornamental plants
Environmental stress in German forests; assessment of critical deposition levels and their exceedances and meteorological stress for crown condition monitoring sites in Germany
Klap, J.M. ; Reinds, G.J. ; Bleeker, A. ; Vries, W. de - \ 2000
Wageningen : Alterra (Alterra-rapport 134) - 73
bossen - bosschade - monitoring - kou - verzuring - vorst - stikstof - zure depositie - stressfactoren - droogte - modellen - luchtverontreiniging - duitsland - forests - forest damage - cold - acidification - frost - nitrogen - acid deposition - stress factors - drought - models - air pollution - germany
Site-specific estimations of meteorological stress and atmospheric deposition were made for the systematic 8 x 8 km2 forest condition monitoring network in Germany for the years 1987-1995. Winter cold and late frost were important temperature stress variables and relative transpiration was a good indicator of drought stress. All variables showed considerable temporal and spatial variation. Present loads of nitrogen and acidity were modelled with an adapted version of the EDACS model and combined withcritical loads and critical deposition levels based on the SMB model. Both present loads and the extents of exceeding showed considerable spatial variation and a clear decrease in time.
Invloed vernalisatie op groei en ontwikkeling bij Gypsophila paniculata 'Perfecta'
Nijssen, H.M.C. ; Mourik, N.M. van - \ 1997
Aalsmeer : Proefstation voor Bloemisterij en Glasgroente (Rapport / Proefstation voor Bloemisterij en Glasgroente 123) - 18
sierplanten - kou - vorst - groei - plantenontwikkeling - rapporten - gypsophila paniculata - ornamental plants - cold - frost - growth - plant development - reports
Verslag van onderzoek aan hyacint 1995
Vreeburg, P.J.M. ; Koster, A.T.J. ; Korsuize, C.A. ; Vlaming - Kroon, E.A.C. - \ 1995
Lisse : Laboratorium voor Bloembollenonderzoek (Rapport bloembollenonderzoek nr. 98) - 37
hyacinthus orientalis - hyacinten - kou - vernalisatie - lichtrelaties - vegetatieve vermeerdering - botrytis - gewasbescherming - hyacinths - cold - vernalization - light relations - vegetative propagation - plant protection
Effect van stikstof en kalium bemesting op de vorstgevoeligheid van Pseudotsuga menziesii
Ruesink, J.B. - \ 1995
Boskoop : Boomteeltpraktijkonderzoek (Rapport / Boomteeltpraktijkonderzoek 38) - 62
kou - oogstschade - bosbouw - beschadigingen door vorst - nederland - stikstof - houtachtige planten als sierplanten - kalium - temperatuur - bomen - pseudotsuga menziesii - cold - crop damage - forestry - frost injury - netherlands - nitrogen - ornamental woody plants - potassium - temperature - trees
Temperatuurbehoefte van lacterende zeugen in relatie tot voeropname, produktie en energieverbruik
Makkink, C.A. - \ 1994
Rosmalen : Praktijkonderzoek varkenshouderij (Proefverslag / Praktijkonderzoek Varkenshouderij P1.105) - 32
diervoedering - dierhouderij - dierfysiologie - lichaamstemperatuur - regulatie van de lichaamstemperatuur - kou - voer - voedingswaarde - productiviteit - rentabiliteit - bescherming - zeugen - thermoregulatie - chemische factoren - fysische factoren - animal feeding - animal husbandry - animal physiology - body temperature - body temperature regulation - cold - feeds - nutritive value - productivity - profitability - protection - sows - thermoregulation - chemical factors - physical factors
Dit rapport is het resultaat van een studie naar de temperatuurbehoefte van lacterende zeugen in relatie tot voeropname, produktie en energieverbruik
Gibberellins and the cold requirement of tulip
Rebers, M. - \ 1994
Agricultural University. Promotor(en): L.H.W. van der Plas; E. Knegt. - S.l. : Rebers - ISBN 9789054853237 - 121
liliaceae - bloembollen - gibberellinen - zaden - stratificatie (zaden) - groei - tulipa - kou - ornamental bulbs - gibberellins - seeds - stratification - growth - cold
<p>Tulip bulbs <em>(Tulipa gesneriana</em> L.), <em></em> with terminal buds containing a complete flower, require a period of low temperature to prepare the bud for floral stalk elongation and full flower development at subsequent higher temperatures. For the cultivar Apeldoorn, a dry- storage treatment of 12 weeks at 5°C prior to planting at 20°C, win lead to proper floral stalk elongation and full flower development. Shorter periods at 5°C usually result in slower shoot elongation and delayed flowering. Without any cold treatment, the growth of the shoot is strongly reduced and often flower abortion occurs. In these processes, the involvement of gibberellins (GAs) has been implicated, because application of GAs could partly replace the cold treatment. In addition, GA biosynthesis inhibitors could reduce the floral stalk elongation of cold-treated bulbs and this effect was reversed by simultaneous application of GA.<p>In horticultural practice, there is a need for a practical assay to test whether a particular bulb has received a proper cold treatment. The amount of GAs or of one particular GA, might provide a suitable parameter in a test for properly cold-treated bulbs.<p>In this study, the role of GAs in the cold requirement of tulip was investigated by analysing the GA levels in cooled and noncooled tulip bulbs, and by studying the effect and metabolism of applied GAs in combination with a' GA biosynthesis inhibitor.<p>An inventory was made of GAs, in sprouts of cooled (12 weeks 5°C) and noncooled bulbs (12 weeks 17°C) (chapter 3). By combined gas chromatography-mass spectrometry (GC-MS) and GC-selected ion monitoring (SIM), GA <sub><font size="-2">1</font></sub> , GA <sub><font size="-2">4</font></sub> , GA <sub><font size="-2">9</font></sub> , GA <sub><font size="-2">12</font></sub> , GA <sub><font size="-2">24</font></sub> , GA <sub><font size="-2">34</font></sub> and three GA-related compounds were detected. They all occurred in sprouts of both cooled and noncooled bulbs. Most of them were found in the conjugated form as well. Among these GAs, GA <sub><font size="-2">4</font></sub> and/or GA <sub><font size="-2">1</font></sub> might be the active forms, the others being precursors (GA <sub><font size="-2">9</font></sub> , GA <sub><font size="-2">12</font></sub> , and GA <sub><font size="-2">24</font></sub> ), or an inactivation product (GA <sub><font size="-2">34</font></sub> ).<p>Using GC-SIM and deuterated GAs as internal standards, the changes in endogenous GA levels were measured in sprouts and basal plates during cooled and noncooled bulb storage, as well as after planting these bulbs (chapter 4). GA <sub><font size="-2">4</font></sub> and GA <sub><font size="-2">24</font></sub> were the major occurring gibberellins, with levels up to ca. 10 ng per sprout or basal plate. GA <sub><font size="-2">1</font></sub> , GA <sub><font size="-2">9</font></sub> and GA <sub><font size="-2">34</font></sub> were present in much lower amounts. The levels of GA <sub><font size="-2">12</font></sub> and of the GA conjugates and GA-related compounds were not analysed.<p>During bulb storage, the level of GA <sub><font size="-2">4</font></sub> per sprout increased, especially in noncooled bulbs. After 12 weeks, these sprouts contained more GA <sub><font size="-2">4</font></sub> and also more GA <sub><font size="-2">1</font></sub> than cooled sprouts. However, sprouts in noncooled bulbs did hardly show any development after planting and it is unlikely that the increased level at the end of bulb storage is correlated with floral stalk elongation at subsequent higher temperatures. In the basal plates no significant changes occurred in the GA levels during storage. Therefore, the GA content in sprouts or basal plates at the end of bulb storage, cannot be used as marker in a test for properly cold-treated bulbs.<p>After planting cooled bulbs, the sprouts started to grow and within the first 11 days the level of GA <sub><font size="-2">4</font></sub> in the floral sulks increased. In planted noncooled bulbs, sprout growth was negligible and an increase in the level of GA <sub><font size="-2">4</font></sub> did not occur.<p>The biological activity of GA <sub><font size="-2">1</font></sub> , GA <sub><font size="-2">4</font></sub> and GA <sub><font size="-2">9</font></sub> , was tested on isolated sprouts, cultivated on a liquid medium <em>in vitro</em> (chapter 5). To compare the sensitivity to exogenous GAs, sprouts from both cooled and noncooled bulbs were used. The growth retardant paclobutrazol was used to study the role of GA biosynthesis. The growth of these isolated sprouts, the response to GAs and the effect of paclobutrazol, appeared to be dependent not only on the pretreatment of the bulbs, but also on the time in the season that the sprouts were isolated and incubated.<p>At early starting dates of incubation, floral stalks from both cooled and noncooled bulbs hardly showed any elongation in the absence of exogenous GA. Paclobutrazol had no effect on floral stalk elongation, and the response to GAs of sprouts from cooled bulbs was greater than the response of sprouts from noncooled bulbs. At later starts, considerable floral stalk elongation already occurred without GA application. Paclobutrazol inhibited this floral stalk elongation, and the growth of sprouts from both cooled and noncooled bulbs was stimulated by GA application. The three tested GAs were not significantly different in stimulating floral stalk elongation. The effect of paclobutrazol. was reversed by simultaneous application of GA. The results of these <em>in vitro</em> experiments demonstrated that, although depending on the time of the year, sprouts from both cooled and noncooled bulbs are responsive to exogenous GAs. Moreover, sprouts from both bulb treatments are capable of GA biosynthesis. The increasing performance of the isolated sprouts when incubated at later starting dates, and the increasing effect of paclobutrazol on these sprouts, suggested an increase in the availability of precursors for the synthesis of GAs. Apparently, low temperatures as well as bulb storage itself enhance GA biosynthesis and GA sensitivity, and consequently floral stalk elongation after planting when conditions are favourable for growth.<p>The isolated sprouts did not develop a full-grown flower without the addition of GA. GA <sub><font size="-2">4</font></sub> was more effective than GA <sub><font size="-2">9</font></sub> in stimulating this flower development. GA <sub><font size="-2">1</font></sub> could also stimulate flower development, but was no more effective than GA <sub><font size="-2">4</font></sub> .<p>The activity of applied GA <sub><font size="-2">9</font></sub> might be due to its conversion to GA <sub><font size="-2">4</font></sub> . GA <sub><font size="-2">4</font></sub> on its turn, might have to be converted to GA <sub><font size="-2">1</font></sub> before becoming biologically active. The metabolism of applied GA <sub><font size="-2">9</font></sub> was studied, with the purpose to investigate whether tulip sprouts are able to metabolize GA <sub><font size="-2">9</font></sub> to biologically active GA <sub><font size="-2">4</font></sub> or GA <sub><font size="-2">1</font></sub> , and whether sprouts from cooled and noncooled bulbs show differences in GA metabolism (chapter 6). [ <sup><font size="-2">3</font></SUP>H]GA <sub><font size="-2">9</font></sub> and [ <sup><font size="-2">2</font></SUP>H]GA <sub><font size="-2">9</font></sub> were applied to isolated sprouts by injection into the floral stalk and the metabolites were analysed in the sprouts after 24 h. According to HPLC analyses, [ <sup><font size="-2">3</font></SUP>H]GA <sub><font size="-2">9</font></sub> was converted to GA <sub><font size="-2">4</font></sub> -like and GA <sub><font size="-2">34</font></sub> -like compounds. The labelled metabolites of [ <sup><font size="-2">2</font></SUP>H]GA <sub><font size="-2">9</font></sub> were identified by GC-SIM, which demonstrated the conversion of [ <sup><font size="-2">2</font></SUP>H]GA <sub><font size="-2">9</font></sub> to [ <sup><font size="-2">2</font></SUP>H]GA <sub><font size="-2">4</font></sub> and [ <sup><font size="-2">2</font></SUP>H]GA <sub><font size="-2">34</font></sub> . Sprouts from both cooled and noncooled bulbs were able to convert GA <sub><font size="-2">9</font></sub> to GA <sub><font size="-2">4</font></sub> and GA <sub><font size="-2">34</font></sub><em>in vitro</em> . No evidence was found for the production of labelled GA <sub><font size="-2">1</font></sub> .In the presence of prohexadione (BX-112), known for its inhibiting effect on 2- and 3β-hydroxylations of GAs, the formation of [ <sup><font size="-2">2</font></SUP>H] metabolites was less or absent.<p>In conclusion, there is no direct correlation between the cold-stimulated growth and a change in the endogenous GA status in sprouts or basal plates during cold bulb storage. Further, the sensitivity to GAs increases in cooled sprouts, but also noncooled sprouts are responsive to applied GAs, and GA sensitivity apparently is not limiting for the development of noncooled sprouts <em>in vitro</em> . After cooled bulb storage, GA biosynthesis is essential for floral stalk elongation to proceed. The increase in the level of GA <sub><font size="-2">4</font></sub> in the growing floral stalks of cooled bulbs, the response of isolated sprouts to GA <sub><font size="-2">4</font></sub> and the inability of isolated sprouts to produce detectable amounts of GA <sub><font size="-2">1</font></sub> from applied GA <sub><font size="-2">9</font></sub> , support the hypothesis that GA <sub><font size="-2">4</font></sub> is the major intrinsically active GA in the floral stalk elongation of tulip.
Heat and mass transfer in frozen porous media
Loon, W. van - \ 1991
Agricultural University. Promotor(en): J. Schenk; I.A. van Haneghem. - S.l. : Van Loon - 204
vibratie - geluidsleer - reflectie - resonantie - thermodynamica - warmte - warmteoverdracht - thermische geleiding - transmissie - hydrodynamica - vloeistoffen (liquids) - vloeistoffen (fluids) - stroming - poreus medium - vorst - bodem - dampdruk - tensiometers - effecten - temperatuur - kou - meting - elektrische eigenschappen - vibration - acoustics - reflection - resonance - thermodynamics - heat - heat transfer - thermal conductivity - transmission - hydrodynamics - liquids - fluids - flow - porous media - frost - soil - vapour pressure - effects - temperature - cold - measurement - electrical properties
<p><TT>In this thesis processes and parameters associated with heat and mass transfer in frozen porous media both on a theoretical and empirical basis are studied. To obtain the required measurements some existing measuring methods needed to be improved.</TT><p><TT>Firstly, an improved model has been developed for the measurement of thermal conductivity with use of the nonsteady-state probe method. The measurements of thermal conductivity indicate four separate effects caused by the freezing process.</TT><p><TT>The second improved measuring method is the measurement of bulk electrical conductivity with use of time-domain reflectometry.</TT><p><TT>And the third improvement is the use of the dispersion theory in the description of relations between water content and bulk electrical conductivity or dielectric constant.</TT><p><TT>This thesis shows that time-domain reflectometry can be used to measure the unfrozen water content and bulk electrical conductivity simultaneously under frozen conditions and that from the latter parameter solute redistribution can be monitored.</TT><p><TT>From the measured heat flows a time delay in the forming of pore ice can be concluded. From the measured moisture transport (resulting in frost heave) a relation with some soil properties could be established. For some of the materials studied a minimum temperature gradient has been observed at</TT>which<TT>heave starts. From this and other results an effort was made to come to a synthesis of the rigid ice concept and the segregation potential concept.</TT><p><TT>The thesis finishes with some recommandations in connection with the improvement of soil structure by freezing, frost heave and artificial ground freezing.</TT>
Don't expose your pigs to sudden draught.
Verhagen, J.M.F. ; Verstegen, M.W.A. - \ 1989
Pigs : an international magazine on pig keeping 5 (1989)6. - ISSN 0168-9533 - p. 23 - 25.
gebouwen - kou - milieubeheersing - verwarming - varkensstallen - biggen - bescherming - buildings - cold - environmental control - heating - pig housing - piglets - protection
Nestverwarmingssystemen voor zogende biggen: gebruikservaringen en energieverbruik
Peerlings, J. ; Klooster, C.E. van 't - \ 1988
Rosmalen : Proefstation voor de Varkenshouderij (Proefverslag / Proefstation voor de Varkenshouderij P1.26) - 40
kou - biggen - varkens - bescherming - cold - piglets - pigs - protection
Elektrische vloerverwarming blijkt een systeem van biggennestverwarming met lage energiekosten te zijn. Van alle systemen zijn de gebruikservaringen vastgelegd, van de elektrische systemen ook het energieverbruik. Vloerverwarming blijkt ook arbeidstechnisch gezien binnen de beproefde systemen het beste te voldoen. Van het wel of niet toepassen van een extra verwarmingslamp tot 3 dagen na het werpen in kraamhokken met vloerverwarming zijn de technische resultaten vergeleken
The effects of low temperature on seedling growth of maize genotypes
Miedema, P. ; Post, J. ; Groot, P.J. - \ 1987
Wageningen : Pudoc (Agricultural research reports no. 926) - 124
groeistadia - gewassen, groeifasen - zea mays - maïs - kou - vorst - growth stages - crop growth stage - maize - cold - frost
Acclimation of growing pigs to climatic environment
Verhagen, J.M.F. - \ 1987
Agricultural University. Promotor(en): A. Hoogerbrugge; Martin Verstegen. - S.l. : Verhagen - 128
varkens - bescherming - kou - lichaamstemperatuur - thermoregulatie - regulatie van de lichaamstemperatuur - dieren - adaptatie - milieu - pigs - protection - cold - body temperature - thermoregulation - body temperature regulation - animals - adaptation - environment
<p>In intensive pig production the climatic environment has an important impact on productivity and health of the animals. Since factors as draught and fluctuating temperatures are known to influence the incidence and severity of <em>Haemophilus pleuropneumoniae</em> infections in growing pigs at the beginning of the fattening period. These aspects of climatic environmment in young growing pigs were studied.<p>It is known that climatic factors influence metabolic rate and energy metabolism of animals. Moreover, acclimation to adverse conditions, <em>e.g.</em> low ambient temperature, may occur. This implicates that the outcome of infection might be related to time of occurrence of climatic stress. This was studied in chapter I. Pigs infected with <em>Haemophilus pleuropneumoniae</em> and exposed to climatic stress (fluctuating temperature and draught) thereafter had a higher mortality and morbidity rate compared with pigs exposed to thermoneutral conditions (25 °C). Specific serum antibody levels of pigs were increased at day 12 p.i. and higher for pigs exposed to climatic stress compared with pigs kept at 25 °C. Infection of pigs with <em>Haemophilus pleuropneumoniae</em> after 12 days of exposure to both conditions (25 °C). vs fluctuating temperature and draught) showed no distinct differences between both groups. Acclimation of pigs could be related to this.<p>Time and day of achievement of acclimation of pigs to different adverse climatic conditions was studied also. Exposure to ambient temperatures of either 25 °C or 15 °C influenced energy metabolism. Pigs housed at 15 °C reduced their <em>ad libitum</em> feed intake during the first 6 days after exposure compared with pigs at 25 °C. Heat production was equal to that of pigs at 25 °C. As a result maintenance requirement was increased by 11% and the amount of energy available for production was lowered. Daily gain and fat deposition were subsequently lowered at 15 °C. At day 11-12 after initial exposure to the climatic treatments differences between the temperature groups were no longer present. The effect of both ambient temperatures on heat production and activity was also studied. Day of acclimation was determined as that day after which heat production or activity-related heat production remained constant.<p>Besides ambient temperature, acclimation was also studied with respect to the occurrence of draught during the night period. Draught was applied at either constant ambient temperatures of 25 °C or 15 °C or fluctuating temperature (25 °C). during the day period and 15 °C). during the night period). Draught consisted of an increased air velocity from &lt; 0.2 m/s to 0.8 m/s with a lower temperature of 5 °C. Acclimation estimated from heat production of pigs at a constant ambient temperature of 25 °C was achieved during the day period at day 5 after initial exposure. At a constant temperature of 15 °C and also at the fluctuating temperature acclimation was delayed with a few days as compared with a temperature of 25 °C and reached at day 8. During the night period acclimation at 25 °C could not be determined since heat production did not alter with increasing daynumber after initial exposure. Acclimation during the night period at 15 °C and at the fluctuating temperature was achieved at day 6 and 3 respectively. This showed that acclimation during the night period differed from that during the day period. Moreover with fluctuating temperature, the temperature during the day period (25 °C). influenced acclimation during the night period (15 °C).<p>The occurrence of draught delayed day of acclimation. At 15 °C and at the fluctuating temperature a "shift" in heat production and activity was found from the day period to the beginning of the night period. For the determination of the day of acclimation at 25 °C, 15 °C or fluctuating temperature this period was omitted first. Data in literature showed that an increase in heat production by 11 kJ per kg metabolic body weight (kg <sup><font size="-2">0.75</font></SUP>) is equivalent to an increase in lower critical temperature (LCT) by about 1 °C. The effect of draught on heat production was expressed as change in LCT. At 25 °C draught increased LCT by 2.8 °C, at 15 °C by 4.2 °C and with fluctuating temperature by 4.5 °C when compared with control groups exposed to a similar temperature. Draught had thus a differential effect on the LCT, depending on the ambient temperature. Draught was applied during three 2-hour periods at night (21.00-23.00 h, 1.00-3.00 h and 5.00-7.00 h) and made it possible to estimate the effect of draught within nights. At 25 °C draught increased LCT by 3.2 °C, at 15 °C by 6.0 °C and with fluctuating temperature by 5.4 °C. It showed that, within nights, influences of draught on heat production were greater.<p>The effect of exposure to various climatic conditions on blood parameters was also studied. Pigs exposed to fluctuating temperature and draught had an increased percentage of lymphocytes and a decreased percentage of neutrophils in peripheral blood after 16 days of exposure.<p>Homeothermic animals maintain a constant ambient temperature. An increased heat loss to the environment will be compensated by an increase in heat production thus enabling body temperature to remain constant. With the use of telemetrical measurements of body temperature the effect of various climatic conditions on body temperature were determined. Results showed that body temperature was not affected by a constant ambient temperature. With application of draught body temperature was changed. A rhythm was found with the occurrence of draught at 25 °C, 15 °C and fluctuating temperature. A rhythm in heat production and activity-related heat production in relation to the occurrence of draught was also present. However rhythm of body temperature was not similar to that of heat production or activity-related heat production. Heat production and also activityrelated heat production were at their maximum directly after the onset of draught, whereas body temperature was lowered first and increased thereafter. Difference in the peak of heat production and body temperature was correlated with the effect of draught on heat production.<p>As a response to infection pigs will alter their set-point temperature and body temperature will incline. Consequently the defence mechanism is increased. Thus lowering body temperature due to sudden changes in climatic environment as with draught, will delay or diminish this enhancement. As a result of the effect of draught on body temperature the ability of animals to cope with infection is impaired.
Influence of external factors on growth and development of sugar-beet (Beta vulgaris L.)
Smit, A.L. - \ 1983
Landbouwhogeschool Wageningen. Promotor(en): L.J.P. Kupers, co-promotor(en): G.J. Vervelde. - Wageningen : Pudoc - 109
beta vulgaris - kou - vorst - zaden - stratificatie (zaden) - suikerbieten - cold - frost - seeds - stratification - sugarbeet
Several trials on the quantitative influence of photophase, chilling (vernalization) and high temperature (devernalization) on bolting of sugar-beet were analysed on the basis of a simple physiological model, in which bolting is considered as the final event of dynamic, momentary and quantitative processes in the plant. Trials in the field and in growth chambers examined factors in chilling and in light response. The inhibitory effect on bolting of high temperatures and the role of photophase in this process was investigated for several periods after vernalization.<p/>Growth and bolting seem to be correlated, as plants with just visible bolting were usually heavier.<p/>A possible relation between bolting resistance and vigour was investigated. Also the influence of photophase and cold treatment on growth was measured in a trial.<p/>Some ways are shown of using a climatic factor like temperature to predict bolting in the field. Finally some recommendations for sugar-beet breeders are drawn up.
Grote vreters groeien ook in de winter snel
Mateman, G. ; Brandsma, H.A. ; Verstegen, M.W.A. - \ 1981
Boerderij 66 (1981)6. - ISSN 0006-5617
kou - energetische waarde - voer - varkens - bescherming - stalvoedering - cold - energy value - feeds - pigs - protection - indoor feeding
Uit klimaatproeven op het Instituut voor Veeteeltkundig Onderzoek te Zeist is gebleken dat varkens, die langdurig te koud gehuisvest zijn, maar die wel extra voer kunnen opnemen, een hoog groeiniveau kunnen handhaven. Voor de vorming van 1 kg lichaamsvet is ongeveer 2,5 maal zoveel energie nodig als voor het vormen van 1 kg vlees. Beschikt een varkensmester over varkens die weinig vet en veel vlees aanzetten, dus goed gezond zijn en goede genetische aanleg hebben, dan zullen deze varkens ook bij een hoog voerniveau een gunstige voederconversie hebben. Dit is in proeven waarbij beperkte en ad lib voeding werden vergeleken ook naar voren gekomen
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