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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    Heat stress tolerance responses in developing tomato anthers
    Bita, Elena - \ 2016
    Wageningen University. Promotor(en): Gerco Angenent, co-promotor(en): Christian Bachem. - Wageningen : Wageningen University - ISBN 9789462577701 - 109
    tomatoes - solanum lycopersicum - anthers - heat stress - stress tolerance - heat tolerance - heat shock - transcriptomics - reproductive performance - gene expression profiling - meiosis - tomaten - solanum lycopersicum - helmknoppen - warmtestress - stresstolerantie - hittetolerantie - hitteshock - transcriptomica - voortplantingsvermogen - genexpressieprofilering - meiose

    Global warming already has and will significantly impact crop productivity and yield in the near future. In order to meet the forecasted requirements of the future agricultural production, a proper assessment of crops environmental stress tolerance needs to be designed and implemented, from the laboratory to field. Genetic variation in the ability of tomatoes to set fruit under high temperature conditions has made selection for heat tolerance possible and multiple opportunities for improvement exist, as tolerance to high temperatures is a multi-genic character involving a complex network of chaperones and other protective proteins acting together to defend the cells from heat injury. Breeding programs involved in the development of heat tolerant cultivars should identify and make use of such tolerance traits already available in collected or wild germplasm.

    The goal of this thesis was to characterize the response to high temperatures in meiotic tomato anthers with contrasting responses to heat and to identify genes that could be related to thermo-tolerance mechanisms during gamete development. Several molecular tools such as transcriptomic profiling by cDNA-AFLP and microarray analysis, RT-PCR or in situ RNA hybridisation were used to achieve this goal.

    The second chapter reviews the effects of heat stress on reproductive flower development, candidate tolerance pathways and methods for production of heat tolerant crops.

    The third chapter provides a general overview of the expression changes occurring in the developing anthers of a sensitive tomato genotype following exposure to a (short and) moderate high temperature stress (MHS). Using a combination of cDNA-AFLP, RT-PCR, and in situ RNA hybridisation, we characterized and verified the general transcriptional response to heat of tomato plants. Our results revealed that approximately 1% of the examined transcript-derived fragments exhibit alterations in expression pattern and the majority of these were down-regulated The putative functions associated with the genes identified by cDNA-AFLP indicated involvement of heat shock, metabolism, antioxidant and developmental processes. Based upon the observed transcriptional changes in response to MHS and on literature sources, we identified a number of candidate transcripts to be involved in heat-tolerance. The spatial expression of several such candidate genes was further examined using in situ RNA hybridisation and this showed that the investigated genes are expressed in the tapetum or/and in developing microspores. Furthermore, the expression of several candidate genes has been quantified by RT-PCR in additional genotypes with different degrees of heat tolerance. The results suggested a correlation between gene expression levels, pollen germination rates and tolerance to heat (Chapter 4).

    In the fourth chapter we proceeded to profile the response to heat of meiotic anthers in a tolerant and a sensitive tomato genotype and investigated the expression of the identified candidate genes in several pairs of contrasting genotypes. Using microarray analysis (for an extensive overview of the meiotic response to heat) and RT-PCR, we were able to clearly distinguish differential responses of the tolerant genotype. After 2h of moderate heat stress, the heat-tolerant genotype exhibits fewer transcriptional changes than the heat-sensitive genotype. In the heat-tolerant genotype, the majority of changes in gene expression is represented by up-regulation, while in the heat-sensitive genotype there is a general trend to down-regulate gene expression soon after MHS. Moreover, the heat-tolerant genotype also shows a different level of constitutive gene expression profiles when compared to the heat-sensitive genotype indicating a difference in genetic adaptation with regards to increased temperatures. The putative functions associated with the genes identified by microarray profiling indicate involvement of heat shock, antioxidant, metabolic, and cell development pathways. Based upon the observed differences in response to MHS we selected a number of candidate transcripts involved in heat-tolerance and confirmed their expression pattern in different tomato genotypes with contrasting responses to heat. The results suggested that the candidate genes are involved in the activation of protection mechanisms in the tomato anthers during moderate heat stress and, could therefore contribute to normal growth and development of the male gametophyte and implicitly a successful fruit set under adverse temperatures.

    In the fifth chapter we tested the hypothesis that heat tolerance is associated with maintenance of organ identity, fertility and lower ABA levels during heat stress (for several tomato genotypes) and analysed the dynamics of ABA accumulation under temperature stress in several tomato genotypes with contrasting responses to heat. Furthermore, pollen germination tests were performed and additional physiological aspects of anther development for each genotype were analysed as well. The general trend observed was the accumulation of lower relative levels of ABA at the end of the experimental period compared to the initial stages in more tolerant genotypes and of higher levels in the sensitive genotypes. We concluded from these results that the morphological changes in the floral tissues and the overall changes in ABA levels are correlated with the molecular responses under increased temperature in the genotypes analysed. Whether these correlations are causally related is not clear; therefore more research is needed to resolve these issues.

    The sixth chapter examines our analysis of the heat stress response in meiotic tomato anthers in a broader scientific context. I discuss the different aspects of our results and present several candidate genes involved in plant thermo-tolerance. In addition, I also discuss the potential involvement of plant growth regulators in plants´ responses to heat stress and suggest various potential follow-up experimental strategies.

    Effect van voerniveau bij drachtige lacterende zeugen op reproductie en conditie = Effect of feeding level in gestating lactating sows on reproduction and condition
    Peet-Schwering, C.M.C. van der; Rommers, J.M. ; Troquet, L.M.P. ; Soede, N.M. - \ 2015
    Wageningen : Wageningen UR Livestock Research (Livestock Research report 861) - 39
    zeugen - voeropname - varkensvoeding - varkenshouderij - lichamelijke fitheid - zogen - voortplantingsvermogen - biggen - lactatie - sows - feed intake - pig feeding - pig farming - physical fitness - suckling - reproductive performance - piglets - lactation
    Op VIC Sterksel is onderzocht wat het effect is van het voerniveau van zeugen tijdens de laatste 8 dagen van een zes weekse lactatie waarin ze ook drachtig zijn op de gewichts- en spekdikte ontwikkeling van de zeugen, de resultaten van de biggen en het aantal levend en dood geboren biggen in de volgende worp. De resultaten van het onderzoek zijn in dit rapport beschreven.
    Snow shoes and sandals? : genetic aspects of heat stress sensitivity and sow reproduction
    Bloemhof, S. - \ 2013
    Wageningen University. Promotor(en): Johan van Arendonk; I. Misztal, co-promotor(en): E.F. Knol; Liesbeth van der Waaij. - S.l. : s.n. - ISBN 9789461735881 - 173
    zeugen - warmtestress - diergenetica - gevoeligheid - geslachtelijke voortplanting - voortplantingsvermogen - kritische temperatuur - hittetolerantie - selectief fokken - genetische correlatie - veredelingsprogramma's - varkensfokkerij - sows - heat stress - animal genetics - sensitivity - sexual reproduction - reproductive performance - critical temperature - heat tolerance - selective breeding - genetic correlation - breeding programmes - pig breeding

    Globally the average size of pig herds are increasing and amount of labour spent per sow / finisher pig is decreasing. These changes require sows which need less management interventions. In addition to easier manageable sows modern genotypes will also need to be more adaptable considering that global temperatures are expected to increase and pork production is partially moving to warmer climates. The end result is that commercial pigs nowadays will potentially face more heat stress challenges during their productive lives.

    In this thesis, a model was developed which was used to estimate upper critical temperatures for sows’ reproductive performance. Additionally the possibility to breed for reduced heat tolerance of sows was investigated. Therefore heritability for the random regression slope of farrowing rate against increasing temperature at day of insemination (= heat tolerance) and the genetic correlation between farrowing rate and heat tolerance was estimated.Commercial production pigs are crossbreds farmed all over the world. In contrast, selection is practiced mainly in temperate climates, in nucleus herds using purebred pigs. The success of genetic selection depends on how much genetic progress is realized in crossbred pigs. Within this thesis these genetic correlations for farrowing rate between purebreds and crossbreds were estimated.

    Sow productivity depends on a number of related traits, such as ovulation rate, the number of litters per sow per year, the number of weaned piglets per sow per year, and the length of productive live. Traditionally pig breeding programs have improved sow productivity by increasing number weaned piglets per sow per year. To improve herd-level litters per sow per year a new trait was proposed called problem free sow production by parity, which incorporates the traits interval weaning first insemination, non-return rate, farrowing rate, and selection for next parity. Heritability of problem free sow production and genetic correlations with other sow production traits were estimated.

    The main conclusion of this thesis was that it is possible to select for improved heat resistance in addition to improved commercial production levels in commercial pigs. However, genetic correlation between production in temperate and hot climates is high. This high correlation implies that, within-line, pigs with the best performance in a hot climate will be the best in temperate climate too. Most important for the success of a pig breeding program is to define appropriate breeding goals which are based on the environment(s) that market pigs are expected to perform in. The overall data collection for the genetic evaluation needs to be done in those specific environments and this will favour pigs which are able to produce over more than one specific environment.

    Reproduction in crabs: strategies, invasiveness and environmental influences thereon
    Brink, A.M. van den - \ 2013
    Wageningen University. Promotor(en): Han Lindeboom, co-promotor(en): Aad Smaal; C. McLay. - S.l. : s.n. - ISBN 9789461735232 - 164
    krabben (schaaldieren) - geslachtelijke voortplanting - geslachtsselectie - groei - voortplantingsvermogen - invasieve soorten - populatiedynamica - omgevingstemperatuur - milieufactoren - mariene ecologie - crabs - sexual reproduction - sexual selection - growth - reproductive performance - invasive species - population dynamics - environmental temperature - environmental factors - marine ecology

    This thesis provides insights into the interconnectedness of crab reproductive biology, the selective forces leading to their development, the possible links to invasiveness and the influences of environmental factors thereon. The empirical data collected and presented in this thesis can be used to compare different crab species and make predictions about the effect of climate change on their population dynamics and invasiveness.
    Two crab species in particular are examined in this thesis, Halicarcinus cookii and Hemigrapsus takanoi , which share similar size and habitat preferences, but have different reproductive strategies and statuses as endemic and invasive. The potential effects of increased water temperature due to climate change on the reproduction and eventual population changes in the species are investigated as well as the possible links reproduction and temperature have with the invasiveness of a species.
    Halicarcinus cookii is an endemic crab to the coasts of New Zealand and is not known anywhere else. The species shows determinate growth, hard shell mating, continuous brood production and ventral seminal receptacles. After the final moult the female produces numerous offspring limited only by sperm availability. With a hard shell the female also avoids mortality resulting from the regular vulnerable soft shell stage. Individuals mature over a range of sizes but do not continue growing after their pubertal moult. With such a terminal moult, brood size is limited by female size.

    Hemigrapsus takanoi is native to the north west Pacific, but has been introduced and is very successful in Europe. The species shows indeterminate growth, hard-shell mating, a defined breeding season and ventral seminal receptacles. With indeterminate growth they continue moulting and growing throughout their adult life. After their pubertal moult, these species can mate throughout the year and produce 2-3 broods between each moult. They are not limited in growth or regeneration of limbs and can safely hide from predators during the vulnerable soft-shell inter-moult period rather than mating which exposes them to predators.

    Despite their different reproductive strategies, broods of both species showed a similar reaction to increased water temperature in that the duration of development of the brood decreased as temperature increased. Extrapolating the results to a climate change scenario, it is suggested that with a temperature rise of 2°C H. cookii could produce one extra brood of over 1000 offspring per female life time, potentially leading to a 10-15% increase in fecundity and possible population growth. As H. takanoi does not show continuous brood production, predicting the effect of temperature rise is more difficult, but evidence suggests that fecundity is also likely to increase in this species with an increase in water temperature.

    Temperature increase may also lead to a change in invasiveness of a species. If areas currently below the optimum temperature for a species become warmer, it is possible that a species may spread to the new locations. Hemigrapsus takanoi may spread further north in Europe than it’s current distribution (assuming it is limited by temperature). Furthermore, if temperatures increase the rate of reproduction in a non-indigenous species, they may become more invasive in their present location.

    The colonisation of a new habitat will involve new interactions, such as predation and competition, with species not previously encountered. The interactions of the two invasive crab species H. takanoi and Hemigrapsus sanguineus with the native Carcinus maenas in the delta waters of SW Netherlands was also investigated in this thesis. Whereas C. maenas was the most common shore crab in these waters, its numbers have declined on the soft sediment substrates during the last 20 years. As the two invasive crab species were first recorded in the Dutch delta in 1999, they could not have initiated the decline of the native C. maenas. However, within a few years H. takanoi completely dominated the intertidal hard substrate environments; the same environments on which juvenile C. maenas depend. On soft sediment substrate the native and invasive crab species are presently more or less equally abundant. Nowadays H. takanoi appears to be a fierce interference competitor or predator for small C. maenas specimens by expelling them from their shelters. However, due to the habitat generalist nature of C. maenas, it is unlikely that the Hemigrapsus species will cause it’s local extinction. More likely is that they will learn to live together.

    The objective to provide new information about a rarely studied species (Halicarcinus cookii) was fulfilled in this thesis and the information can be used as bases for comparison for future research.

    The hypothesis that temperature has no effect on the reproductive rate of crabs was rejected as both study species showed similar increases in brood development rate with increased temperatures. This suggests that global temperature rises may increase the reproductive rate of wider crab populations.

    The hypothesis that the arrival, presence and effect of Hemigrapsus takanoi in the Dutch delta waters has had no effect on the native green crab Carcinus maenas was complicated by the fluctuations and the decrease in C. maenas numbers prior to the arrival of H. takanoi. It was concluded that while H. takanoi did not cause the initial decrease in the C. maenas population, it did take advantage of it and now dominates niches previously occupied by juvenile C. maenas where size dependent competition and/or predation on juvenile C. maenas occurs.

    The second parity sow : causes and consequences of variation in reproductive performance
    Hoving, L.L. - \ 2012
    Wageningen University. Promotor(en): Bas Kemp, co-promotor(en): Nicoline Nieuwenhuizen-Soede. - S.l. : s.n. - ISBN 9789461731470 - 171
    varkens - zeugen - voortplanting - voortplantingsvermogen - adaptatiefysiologie - pigs - sows - reproduction - reproductive performance - adaptation physiology

    Many sows show reduced litter sizes in their second parity compared with their first parity. The aim of the current thesis was to describe causes and consequences of variation on second parity reproductive performance and to evaluate if feeding strategies during early gestation affect reproductive performance and sow body weight recovery after first lactation. In a first study, effects of sow weight development from first insemination up to first weaning on second parity reproductive performance were studied. Weight gain from first insemination up to first weaning showed a positive effect on non-pregnancy as well as on litter size, especially on a farm where gilts were relatively young and light at time of first insemination. In a second study, effects of weight loss during lactation were evaluated on embryonic survival and metabolic parameters during lactation and gestation in primiparous sows that were fed close to ad libitum. Sows with a high (>13.8%) weight loss showed a lower embryonic survival and fewer vital embryos at day 35 of gestation compared with sows with a lower weight loss, whilst no differences in metabolic parameters (IGF-1, NEFA, urea) were seen. The fact that the number of implantation sites was lower in high weight loss sows compared with low weight loss sows indicates that the negative effects of weight loss were already present during late lactation or early gestation. In a third study, a data-analysis using 46,500 sows was performed to assess relations between second parity performance and reproductive performance in later parities. Results showed that farrowing rate and litter size in parity 3 and up, as well as parity at culling, were related to second parity reproductive performance. These relations with second parity litter size were affected by first parity litter size. In practice, feed allowance during early gestation is often limited and might not be sufficient to support growth and recovery from lactation. The question was therefore raised if increased feed or protein intake during early pregnancy could improve litter size. In two experiments, the effects of an altered feeding strategy during the first month of gestation on farrowing rate and litter size (exp. 1) and embryonic survival and embryonic and placental development and metabolic parameters (exp. 2) were assessed. In Experiment 1, a 30% higher feeding level increased litter size with two piglets, without negatively affecting piglet birth weight. In Experiment 2, designed to find a physiological explanation for these results, an increased feeding level did not affect embryonic survival, embryonic development or placental development. Furthermore, no relations with metabolic parameters were found. From this thesis it can be concluded that second parity reproductive performance is related to reproductive performance in later parities. In order to improve second parity reproductive performance, weight loss during first lactation should be limited and gilts should be heavier at first weaning than at first insemination. Further, increased feeding levels during early gestation improve sow body weight recovery, without negatively affecting reproductive performance.

    Post weaning altrenogest use in sows: follicle growth, endocrine profiles and subsequent fertility
    Leeuwen, J.J.J. van - \ 2011
    Wageningen University. Promotor(en): Bas Kemp, co-promotor(en): Nicoline Nieuwenhuizen-Soede. - [s.l.] : S.n. - ISBN 9789085859963 - 144
    zeugen - synthetische progestogenen - spenen - voortplantingsvermogen - eierstokfollikels - rijpen - endocrinologie - vruchtbaarheid - dierfysiologie - dierlijke productie - varkenshouderij - sows - synthetic progestogens - weaning - reproductive performance - ovarian follicles - maturation - endocrinology - fertility - animal physiology - animal production - pig farming

    A severe negative energy balance during first lactation may result in poor reproductive performance in the second litter. Allowing the sow recovery time after weaning by inseminating the sow the second estrus after weaning (skip a heat) improves reproductive performance. Postponing estrus for a shorter period after weaning using daily altrenogest administration has also been found to influence reproductive performance. The aim of this thesis was to develop a better understanding of consequences of altrenogest after weaning for follicle development and subsequent reproductive performance. Therefore, a first experiment investigated follicle development during and after post weaning altrenogest treatments and related this to subsequent fertility. It showed that follicle size increased during altrenogest treatment (independent of dose and duration), but no effects were found on fertility parameters on day 5 of gestation. Therefore, a second experiment studiedthe effect of duration of treatment on follicle development and subsequent farrowing rate and litter size. This experiment showed again an increase in follicle size and also showed that long altrenogest treatments (15 d) improve fertility, but that shorter treatments (8 d) reduce farrowing rates in sows with large follicles at weaning. So, to prevent outgrowth of follicles before weaning a third experiment started altrenogest treatment 3 d before weaning. This did not suppress follicle growth, but fertility was improved after altrenogest treatment in primiparous sows with compromised body condition at weaning. A fourth experiment attempted to stimulate follicle growth before weaning using split-weaning (reducing litter size to the 6 smallest piglets 3 d before complete weaning) and found that split-weaning resulted in lower embryonic survival, especially in sows with large follicles at weaning or high follicle growth during treatment. Because in all experiments sows showed follicle growth during altrenogest treatment, it was suspected that LH release was not completely suppressed during altrenogest treatment. Therefore, a fifth experiment investigated LH pulsatility during the last day of altrenogest treatment and indeed showed that LH release was suppressed during only a part of the 24 h between altrenogest administrations. Finally a last experiment showed a release pattern of both FSH and estradiol that varied over the day related with the moment of daily altrenogest administration. Further, a decrease of estrogenic activity was found during the second week of post weaning altrenogest treatment, probably as a result of reduced LH responsiveness. The level of estrogenic activity was related to weight loss during lactation. Therefore, it is assumed that LH and FSH release during altrenogest treatment stimulate follicle growth, but that levels are not high enough to sustain outgrowth of the follicles to pre-ovulatory sizes and, as a result, follicles go into atresia after on average 5-8 d of treatment. This may explain why long altrenogest treatments (12-15 d) result in improved fertility, short altrenogest treatments (3-4 d) have little effect on fertility and intermediate altrenogest treatments (5-8 d) may reduce fertility. As there is large variation between sows (parity, lactational burden, follicle size), this may also affect their response to altrenogest treatment. In general, to improve reproductive performance, it is recommended to start altrenogest treatment 3-6 h before weaning and to apply intermediate treatments (5-8 d) only in primiparous sows that suffered a severe lactational burden and are in low body condition at weaning.

    Broedsucces van kustbroedvogels in de Waddenzee in 2007 en 2008
    Kleunen, A. van; Koffijberg, K. ; Boer, P. ; Nienhuis, J. ; Camphuysen, C.J. ; Schekkerman, H. ; Oosterbeek, K.H. ; Jong, M.L. de; Ens, B.J. ; Smit, C.J. - \ 2010
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-werkdocument 227) - 73
    broedvogels - watervogels - voortplantingsvermogen - kustgebieden - monitoring - populatiedynamica - waddenzee - breeding birds - waterfowl - reproductive performance - coastal areas - monitoring - population dynamics - wadden sea
    Voor het derde en vierde opeenvolgende jaar werd het broedsucces van een aantal kustbroedvogels in de Waddenzee bepaald. Van Eider, Scholekster, Kluut, Kokmeeuw, Zilvermeeuw en Visdief, alsmede van Kleine Mantelmeeuw en Noordse Stern werd informatie verzamelen over het nestsucces en uitvliegsucces (het uiteindelijke broedsucces). Kennis over de jaarlijkse variatie in broedresultaten bij de verschillende soorten is van belang als een early warning systeem om de 'kwaliteit' (het reproducerend vermogen) van de vogelpopulaties in de Waddenzee te volgen en de achterliggende processen van populatieveranderingen te doorgronden. Directe aanleiding voor het project vormde de evaluatie van de effectiviteit van het nieuwe schelpdiervisserijbeleid en de mogelijke gevolgen voor de voedselvoorziening van schelpdieretende vogels.
    Effecten van de visserij gedurende het voortplantingsseizoen op het duurzaam beheer van visbestanden: een uitgebreide Nederlandse samenvatting
    Overzee, H.M.J. van; Rijnsdorp, A.D. - \ 2010
    IJmuiden : IMARES (Rapport / IMARES Wageningen UR 076/10) - 21
    kuitschieten - periode van kuitschieten - visserij - voortplantingsvermogen - gedrag - visserij-ecologie - spawning - spawning season - fisheries - reproductive performance - behaviour - fisheries ecology
    In opdracht van Stichting Vis & Seizoen heeft IMARES een uitgebreide literatuurstudie uitgevoerd naar de mogelijke effecten van de visserij tijdens het voortplantingsseizoen. Dit rapport geeft een uitgebreide Nederlandse samenvatting van het Engelstalige rapport “Effects of fisheries during the spawning season: implications for management”.
    Implications of fisheries during the spawning season for the sustainable management and recovery of depleted fish stocks: a conceptual framework
    Rijnsdorp, A.D. - \ 2009
    IJmuiden : IMARES (Report / IMARES Wageningen UR no. C093.09) - 13
    kuitschieten - periode van kuitschieten - visserij - voortplantingsvermogen - gedrag - visserij-ecologie - spawning - spawning season - fisheries - reproductive performance - behaviour - fisheries ecology
    Fishing during the spawning season may negatively affects the reproductive potential and reproductive dynamics of exploited fish stocks due to a variety of mechanisms such as the disturbance of the natural spawning behaviour, effects on the age, size and sex composition of the spawning population and effects on the population genetics. The effect may differ between species in relation to the spawning strategy and population dynamic characteristics. Based on first principles of reproductive biology, population biology and fishing methods, a theoretical framework is developed on the effects of fishing during the spawning period. This framework is used to structure a review of the available scientific evidence. Implications of the findings on the recovery of depleted fish stocks and the sustainability of exploitation will be discussed and illustrated for a selection of North Sea fish stocks (flatfish, roundfish and pelagic).
    Broedsucces van kustbroedvogels in de Waddenzee in 2006: rapport in het kader van het WOT Programma Informatievoorziening Natuur i.o. (WOT IN)
    Boer, P. de; Oosterbeek, K.H. ; Koffijberg, K. ; Ens, B.J. ; Smit, C.J. ; Jong, M.L. de - \ 2008
    Wageningen : Alterra (IMARES-rapport C036/08) - 41
    broedvogels - monitoring - populatiedynamica - voortplantingsvermogen - waddenzee - breeding birds - monitoring - population dynamics - reproductive performance - wadden sea
    Dit rapport presenteert de resultaten van het ‘Reproductiemeetnet Waddenzee’ dat door IMARES en SOVON Vogelonderzoek Nederland sinds 2005 in de Waddenzee wordt gecoördineerd in het kader van de Wettelijke Onderzoekstaken Informatievoorziening Natuur. Doel van het meetnet is het vaststellen van het reproductief vermogen van een representatieve selectie van broedvogels in de Waddenzee (Eider, Scholekster, Kluut, Kokmeeuw, Zilvermeeuw, Visdief). Afgezien van Visdief laten alle soorten op dit moment een negatieve trend in aantallen zien. Het meetnet brengt het jaarlijkse broedsucces in kaart en kan daarmee het beleid voeden met informatie over de ‘kwaliteit’ van de betrokken vogelpopulaties. Uit de verzamelde gegevens blijkt dat in 2006 bij de meeste soorten sprake was van een beneden-gemiddeld broedsucces. Vooral bij Scholekster, Kluut en Zilvermeeuw is het aannemelijk dat het langdurig uitblijven van goede broedresultaten een belangrijke factor is die de huidige afname verklaart.
    Sekspartners niet te vinden voor de Europese aal
    Dekker, W. - \ 2007
    Visionair : het vakblad van sportvisserij Nederland 1 (2007)4. - ISSN 1569-7533 - p. 7 - 10.
    european eels - palingen - voortplanting - populatiedichtheid - achteruitgang (decline) - kuitschieten - europa - visserij - verontreiniging - vruchtbaarheid - bescherming - beleid - voortplantingsvermogen - european eels - eels - reproduction - population density - decline - spawning - europe - fisheries - pollution - fertility - protection - policy - reproductive performance
    Het gaat niet goed met de Europese aal. Sinds 1980 is de intrek van glasaal met meer dan 95% afgenomen. Overigens daalden de populaties en de commerciële vangsten al vanaf 1960. De oorzaken van deze afname zijn niet duidelijk. Het ligt voor de hand dat een combinatie van factoren (aalscholvers, afdammingen, inpolderingen, vervuiling, visserij en ziektes) de aal fataal is geworden. De achteruitgang van de glasaal begon plotseling en deed zich voor in heel Europa. Dat wijst op één gemeenschappelijke oorzaak. Waaarschijnlijk is de schieraal op de paaigronden tegenwoordig te eenzaam om zich nog succesvol te kunnen voortplanten
    Optimaal klimaat en energiebesparing in de kraamstal: vloerkoeling voor zeugen
    Wagenberg, A.V. van; Claessen, P.J.P.W. ; Binnendijk, G.P. - \ 2005
    Lelystad : Animal Sciences Group / Praktijkonderzoek (PraktijkRapport / Animal Sciences Group, Praktijkonderzoek : Varkens ) - 20
    huisvesting, dieren - varkens - zeugen - kraamstallen - koeling - vloeren - dierenwelzijn - voeropname - voortplantingsvermogen - warmtepompen - innovaties - energiebesparing - animal housing - pigs - sows - farrowing houses - chilling - floors - animal welfare - feed intake - reproductive performance - heat pumps - innovations - energy saving
    Kraamzeugen hebben moeite hun lichaamswarmte aan de omgeving af te geven. Koelen van de vloer onder de zeug (¿cool-sow¿ vloersysteem) verhoogt het thermische comfort. In dit praktijkonderzoek is vastgesteld dat kraamzeugen op het cool-sow systeem gemiddeld 12% hogere voeropname hebben en 8% zwaardere biggen bij het spenen. Het liggedrag van de zeug veranderde niet. De warmte uit de vloer kan via een warmtepomp gebruikt worden voor stalverwarming. De economische betekenis van de verbeterde technische resultaten dient hoger te zijn dan ¿ 5,- per productieve zeug per jaar.
    Long-term performance and behavior of sows fed high levels of non-starch polysaccharides
    Peet-Schwering, C.M.C. van der - \ 2004
    Wageningen University. Promotor(en): Martin Verstegen; Bas Kemp, co-promotor(en): Leonard den Hartog. - [S.I.] : S.n. - ISBN 9789085040682 - 141
    zeugen - varkens - zwangerschap - lactatie - polysacchariden - voer - samenstelling - voortplantingsvermogen - abnormaal gedrag - diergedrag - zeugenvoeding - diervoeding - dierenwelzijn - sows - pigs - pregnancy - lactation - polysaccharides - feeds - composition - reproductive performance - abnormal behaviour - animal behaviour - sow feeding - animal nutrition - animal welfare

    The main objective of this thesis was to investigate the long-term effects of feeding sows high levels of dietary fermentable non-starch polysaccharides CNSP) (i.e., NSP from sugar beet pulp) restrictedly or ad libitum during gestation or ad libitum during lactation on behavior, reproductive performance, and development in body weight and backfat thickness. During gestation, sows were group-housed. Feeding gestating sows a high level of dietary fermentable NSP restrictedly reduced the frequency of total non-feeding oral activities in gestation compared with a starch diet. Feeding sows a high level of dietary fermentable NSP during lactation reduced the frequency of total non-feeding oral activities during subsequent gestation compared with a starch diet. Body weight and backfat gains during gestation were lower in sows fed a high level of dietary fermentable NSP restrictedly during gestation over three successive parities than in sows fed a starch diet restrictedly. These results indicate an overestimation of the energy value of fermentable NSP. Body weight and backfat losses during lactation were less in sows fed a high level of dietary fermentable NSP during gestation than in sows fed a starch diet. Sows fed a high level of dietary fermentable NSP during lactation lost more backfat during lactation than sows fed a starch diet. The number of live born piglets was 0.5 piglet higher in sows fed a high level of dietary fermentable NSP from weaning until mating and during subsequent gestation than in sows fed a starch diet. It may be that this effect can be attributed to feeding sows a high level of dietary fermentable NSP from weaning until mating. Lactation diet did not affect the number of live born piglets in the following parity. Gestating sows that were fed a high level of dietary fermentable NSP ad libitum during three successive parities ate 1.3 kg/d more during gestation than sows that were fed a starch diet restrictedly (4.2 versus 2.9 kg/d), resulting in higher body weight and backfat gains during gestation and greater losses in body weight and backfat during lactation. Feed intake during lactation was similar in sows that were fed restrictedly or ad libitum during gestation. Reproductive performance was not affected by feeding gestating sows a high level of dietary fermentable NSP ad libitum. Ad libitum fed sows spent 90 min/d eating whereas restrictedly fed sows spent 24 min/d eating. An increase in time spent eating is associated with a reduction in feeding motivation and in stereotypic behaviors. In conclusion, feeding gestating sows a high level of dietary fermentable NSP reduces the level of stereotypic behavior in gestation compared to a starch diet. Feeding sows a diet with a high level of fermentable NSP during lactation has an additional reducing effect on the development of stereotypic behavior in subsequent gestation. Reproductive performance is not negatively affected by feeding gestating sows a diet with a high level of fermentable NSP (i.e. NSP from sugar beet puIp) restrictediy or ad libitum during three successive parities compared to feeding gestating sows a starch diet restrictedly.

    Fertility, aging and the brain neuroendocrinological studies in female rats
    Franke, A.N. - \ 2003
    Wageningen University. Promotor(en): V.M. Wiegant, co-promotor(en): E.M. van der Beek. - [S.l.] : S.n. - ISBN 9789058088796 - 176
    ratten - vruchtbaarheid - voortplantingsvermogen - verouderen - hersenen - neurofysiologie - endocrinologie - rats - fertility - reproductive performance - aging - brain - neurophysiology - endocrinology
    It is well known that fertility decreases in female mammals with advancing age. In women this decrease already starts around the age of 30 and shows a large variation between individuals. The aim of this thesis was to elucidate changes in the reproductive system, especially in the brain, that may underlie the early decline in fertility with age. To this end,neuroendocrinologicalstudies were performed in young and middle-aged females of two rat strains known to differ in the onset of infertility: theWistar(WU) and (UxRP)F1strain.

    The results of the present thesis confirm the idea that the attenuation of theluteinizinghormone (LH) surge is one of the first indications of reproductive aging in rats. The LH surge is responsible for ovulation. It is induced by feedback mechanisms of ovarian steroid hormonesestradioland progesterone on the brain (i.e. on the secretion ofgonadotropin-releasing hormone) and pituitary gland (i.e. on the secretion of LH and follicle-stimulating hormone (FSH)) that become operative when the ovarian follicles are matured, and involves estrogen and progesterone receptors in the brain.

    Our results indicate that the attenuation of the LH surge in middle-aged rats likely results from an altered response of the brain toestradioland possibly also progesterone feedback, since we found a dramatic decrease in the number ofestradioland progesterone-containing neurons in several brain areas known to be crucially involved inneuroendocrineregulation of the reproductive axis. In contrast,estradioland progesterone levels were increased ((UxRP)F1) or even unchanged (Wistar) and the pituitary LH response toGnRHas well as the follicular progesterone production during the LH surge appeared to be comparable between young and middle-aged rats. This suggests that pituitary and ovary functions were still intact. Therefore, changes at the level of the brain may be at the start of the decline in fertility with age in rats.

    Interestingly, we found strain differences in the regulation of the reproductive axis. There was, for instance, a difference between F1 andWistarrats in the magnitude of the LH surge (F1>Wistar) and the magnitude of the pituitary LH response toGnRH(F1<Wistar). Also, middle-aged F1 rats appeared to be reproductively aged to a further extend compared toWistarrats, as judged by the number of changes in the reproductive system.

    Although in women ovarian aging appears to be the dominant reason for fertility decline, there is evidence for considerable variation between individuals in the mechanisms underlying reproductive aging. Based on our present findings and literature, we hypothesize that hypothalamic aging may also contribute to the decline in fertility in some women.

    Onbeperkt voeren drachtige zeugen beinvloedt reproductie niet
    Peet-Schwering, C.M.C. van der; Plagge, J.G. - \ 2003
    Praktijkkompas. Varkens 17 (2003)3. - ISSN 1570-8578 - p. 10 - 11.
    varkenshouderij - zeugen - zeugenvoeding - varkensvoeding - voer - onbeperkte voedering - voedering - gerantsoeneerde voeding - zwangerschap - prestatieniveau - worpresultaten - biggenproductie - zeugvoortplanting - voortplanting - voortplantingsvermogen - gewicht - gewichtstoename - lichaamsvet - rugspek - vetdikte - groepshuisvesting - voedersystemen - pig farming - sows - sow feeding - pig feeding - feeds - unrestricted feeding - feeding - restricted feeding - pregnancy - performance - litter performance - piglet production - sow reproduction - reproduction - reproductive performance - weight - weight gain - body fat - backfat - fat thickness - group housing - feeding systems
    Het gedurende drie opeenvolgende pariteiten onbeperkt voeren van drachtige zeugen met een aangepast voer beonvloedt de reproductieresultaten niet in vergelijking met het beperkt voeren van een gangbaar zeugenvoer. Na drie worpen zijn de onbeperkt gevoerde zeugen wel 25 kg zwaarder dan de beperkt gevoerde zeugen en hebben ze 3 mm meer spek aangezet.
    Strategies for rearing of rabbit does
    Rommers, J.M. - \ 2003
    Wageningen University. Promotor(en): Bas Kemp; J.P.T.M. Noordhuizen, co-promotor(en): R. Meijerhof. - Veenendaal : Universal Press - ISBN 9789058089342 - 169
    konijnen - vrouwelijke dieren - konijnenvoeding - voedingsrantsoenen - leeftijd bij eerste inseminatie - lichaamsgewicht - lichaamssamenstelling - voortplantingsvermogen - worpgrootte - dierhouderij - kweken - rabbits - female animals - rabbit feeding - feed rations - age at first insemination - body weight - body composition - reproductive performance - litter size - animal husbandry - rearing
    This thesis describes the effects of different rearing strategies for young rabbit does on body development and reproduction performance. In current rearing, does are often fed to appetite from weaning to first insemination. First insemination is applied when 75 to 80% of mature body weight (BW) is reached, that occurs around 14 to 16 weeks of age. Under current rearing, young does loose significant part of their fat and energy reserves during first lactation. This seems related to the decreased reproductive performance and high replacement rate of young does, that are undesired from both economic and welfare point of view. Feed intake during lactation seems to be the limited factor. The objectives of this thesis were to optimize body development and feed intake capacity of young does to improve their reproductive performance and to prolong their lifespan.

    In Chapter 1, literature on body growth and body development of rabbits is summarized and management practices and factors that could be relevant during the rearing period to stimulate feed intake and body development are reviewed. Body development in rabbits is characterized by a high growth rate of organs and tissues at early age (before 12 weeks). After 12 weeks of age, mainly fat depots are being formed. Feeding level seemed an important factor to regulate body growth and development together with age of first insemination.

    Therefore, several experiments were performed, in which the level of feed intake and the age of first insemination on body development and composition, feed intake, reproductive performance, and culling rate of does were studied. Feeding level was manipulated in two successive periods during rearing; 1) the period before weaning (30 days of age) in which kits depend on their mother's milk for nutrient intake, and 2) the period after weaning in which kits eat solid food. Rearing period ended at first insemination, that was applied at 14.5 or 17.5 weeks of age.

    In Chapter 2, nutrient intake in the pre-weaning period was investigated. Milk intake was manipulated by varying the number of suckling kits in a litter. Kits were raised in litters of 6, 9 or 12 kits (LS6, 9, 12). Milk intake in the pre-weaning period affected body growth during rearing and BW at first mating (at 14.5 wk of age). Kits raised in small litters (LS6) were heavier at first mating than kits raised in large litters (LS12). Kits raised in litters of nine were able to compensate for the differences in BW at weaning and reached similar BW as LS6 at end of rearing. The amount of milk intake in the pre-weaning period affected body composition at first mating. Ash content (bone formation) was not improved in heavy does (LS6), but they had more fat tissue and energy than small does (LS12). Heavier does (LS6, and 9) produced more kits (+ 1.1 and + 2.2, respectively) than small does (LS12) in the first parity. Feed intake during first lactation was not affected. In the second parity, no differences in BW, feed intake or reproductive performance were found among treatments. Treatment did not affect culling rate. Does which had not become pregnant of the first insemination at 14.5 wk of age were re-inseminated at 17.5 wk of age. Reproductive performance of these does was significantly improved in the first parity.

    In Chapter 3, data of Chapter 2 and a set of unpublished data were used to investigate the effect of BW at 14.5 week of age on subsequent reproduction. Does were divided in three classes based on their BW at first insemination (14.5 week of age) (< 3.5, 3.5 - 4, > 4 kg, respectively). Differences in BW at 14.5 week of age were caused by difference in growth potential and feed intake during rearing. Heavy does (> 4 kg) were does with high voluntary feed intake, but according to their gain to feed ratio at end of rearing, no excessive fat deposition could have occurred. However, the fact that they were heavier implicates that they will have more body reserves in terms of protein and fat. Extra BW at start of reproduction improved litter size in the first parity. Heavy does at first insemination (BW > 4 kg) produced more kits (+ 2.5) compared to small does (BW < 3.5 kg). Extra BW at start did not contribute to an improved feed intake or increased BW development during reproduction and had no effect on culling.     

    In Chapter 4, the effect of BW and age of first insemination on body development, body composition, and puberty characteristics at the end of rearing were studied. Does were fed ad libitum (AL) or restrictive ( R) and were inseminated at 14.5 or 17.5 week of age. Feed restriction was used to manipulate body development by preventing excessive fat deposition and stimulating sexual development. With the feed restriction we succeeded in "creating" does, which had similar body composition and body weight, but differed three weeks in physiological age (14.5 vs. 17.5), whereas puberty characteristics were comparable. Does fed to ad libitum and mated at 17.5 week of age were heaviest, contained more fat and had the best puberty characteristics. Does fed restrictively and mated at 14.5 weeks of age were physiologically too immature for reproduction. Only two of the 16 does (12.5%) fed restrictively were receptive at first insemination. In five of the 10 does that were killed to determine body composition corpera lutea were found, and only one doe had embryos.

    In Chapter 5, the effect of the treatments tested in Chapter 4 were investigated on performance in the reproductive period. Based on the results in Chapter 4, restrictive feeding and mating at 14.5 wk of age was not applied. Does fed ad libitum and mated at 17.5 week of age (AL-17.5) were heaviest at first insemination. Although these does were older and had more body reserves, reproductive performance was not improved. Heavier BW at the same age (AL-17.5 and R-17.5) resulted in a reduced feed intake during first gestation (-25%) and first lactation (-10%), probably due to the high amount of body fat. This resulted in weight loss during first gestation (-6%) and decreased litter weights (-19%) and litter growth (-14%) in the first parity. Although AL-14.5 and R-17.5 does had similar BW and body composition at first insemination, R-17.5 does produced more alive born kits (+ 1.4) and weaned more kits (+ 0.6) in the first parity. Feed intake in the first parity was similar. The ad libitum fed does inseminated at 14.5 week of age gained weight in the first gestation period as well as in the first lactation. Competition for nutrients between body growth and production must have occurred, and resulted in smaller litters and lower milk production. This could indicate that AL-14.5 does were physiological not mature enough for reproduction. Effect of rearing strategies was limited to the first parity. Culling rate of does during the first three parities was not affected by rearing strategy.

    In Chapter 6, an attempt was made to improve litter size after first insemination by restricting feed intake during the first 10 days of gestation. Feed intake in first 10 days of gestation did not affect kindling performance of young does. However, further analysis on ad libitum fed does revealed an effect of feed intake in the last week of gestation on kit survival and birth weight. In does with the highest feed intake during the last week of gestation, the lowest number of litters with stillborn kits with the highest birth weight was found. Feed intake in the last week of gestation was not influenced by feed restriction in early gestation.

    In the General Discussion, the consequences of rearing strategies for production were further analyzed and discussed based on BW at first insemination. Body weight at first insemination was divided into six BW-classes from very small (< 3.5 kg) to very heavy (> 4.5 kg). The effect of BW on reproductive parameters was analyzed for the following rearing strategies: AL-14.5, AL-17.5, and R-17.5, using the data of Chapter 2, a set of unpublished data also used in Chapter 3, and data of Chapter 5. Kindling rate was not affected by rearing strategy.

    In all rearing strategies, litter size increased when does were heavier, although this relationship was most profound in AL-14.5. Litter size was optimized between eight and nine kits in does weighing approximately 4 kg at first insemination. Feeding strategy during rearing influenced the uniformity in BW of does at first insemination. In AL-14.5 does, more than 70% of the does were smaller than 4 kg at first insemination. In does smaller than 4 kg litter size was reduced by approximately 1.5 kit. In AL-17.5 does, 75% of the does were heavier than 4 kg. Body composition determined in Chapter 4, revealed that heavy does have more fat. Based on results in Chapter 5, in does with excessive fat depots, the percentage of does with stillborn kits in their litter will be increased, because feed intake during first gestation is decreased.

    In R-17.5 does, the percentage of does that weighed around 4 kg at first insemination was 60 to 80%. In these does litter size was improved, because the percentage of small animals (with low litter size) as well as the percentage of very heavy animals (with high stillbirth) is reduced.

    There was not a clear relationship between milk production and BW at first insemination. However, in R-17.5 does milk production was higher than in AL-14.5 and 17.5 does, independent of BW-class. The difference in milk production between R-17.5 and Al-17.5 could be explained by the higher feed intake of R-17.5 in the first gestation and lactation period. The difference in milk production between R-17.5 and AL-14.5 could be explained by the fact that AL-14.5 gained weight during first gestation as well as during first lactation. Competition for nutrients between body growth and production must have occurred, and resulted in smaller litters and lower milk production. The higher milk production of R-17.5 does resulted in higher kit weight at weaning. The best reproductive performance in the first parity was found in R-17.5 does. Rearing strategies only affected body weight development, feed intake and reproductive performance in the first parity. Long-term effects over three parities were absent and rearing strategy did not influence culling rate of does.
    Meer biggen met bietenpulp in zeugenvoer
    Peet-Schwering, C. van der; Binnendijk, G. - \ 2002
    Praktijkkompas. Varkens 16 (2002)6. - ISSN 1570-8578 - p. 16 - 17.
    varkens - varkenshouderij - zeugen - varkensvoeding - voer - voersamenstelling - zwangerschap - lactatie - voortplanting - voortplantingsefficiëntie - voortplantingsvermogen - prestatieniveau - bietenpulp - pigs - pig farming - sows - pig feeding - feeds - feed formulation - pregnancy - lactation - reproduction - reproductive efficiency - reproductive performance - performance - beet pulp
    Het geven van een bietenpulp voer tijdens de dracht en een zetmeelrijk voer tijdens de lactatie is een goede voerstrategie voor zeugen. Voer met 40% bietenpulp tijdens de dracht verhoogt het aantal levend geboren biggen met 0,5 big. Het verstrekken van een zetmeelrijk voer tijdens de lactatie verhoogt de voeropname van de zeugen met 0,4 kg per dag. De verplichting om guste en drachtige zeugen dagelijks enig ruwvoer te geven kan dus een positief effect hebben op de reproductie van zeugen
    Ruwecelstofrijke voeders voor zeugen: effect op reproductie en gedrag
    Peet-Schwering, C.M.C. van der - \ 2002
    Lelystad : Praktijkonderzoek Veehouderij (Praktijkrapport. Varkens 10) - 24
    zeugen - varkensvoeding - voer - ruwvoer (roughage) - polysacchariden - zetmeel - zwangerschap - lactatie - diergedrag - abnormaal gedrag - dierenwelzijn - voortplantingsvermogen - sows - pig feeding - feeds - roughage - polysaccharides - starch - pregnancy - lactation - animal behaviour - abnormal behaviour - animal welfare - reproductive performance
    Op het Praktijkcentrum Rosmalen is onderzoek gedaan naar het effect van het verstrekken van voeders met een hoog zetmeelgehalte of een hoog gehalte aan verteerbare overige organische stof (= VOOS) tijdens de dracht, lactatie of dracht en lactatie op de ontwikkeling van gewicht en spekdikte en reproductieresultaten bij zeugen.
    Vaste groepen Lf wisselgroepen
    Kiezebrink, M. ; Mheen, H. van der - \ 2002
    Praktijkkompas. Varkens 16 (2002)2. - ISSN 1570-8578 - p. 8 - 9.
    varkenshouderij - varkens - zeugen - huisvesting, dieren - groepen - groepsgrootte - diergedrag - groepsinteractie - groepsgedrag - zeugvoortplanting - voortplanting - voortplantingsvermogen - prestatieniveau - onderzoek - landbouwkundig onderzoek - groepshuisvesting - pig farming - pigs - sows - animal housing - groups - group size - animal behaviour - group interaction - group behaviour - sow reproduction - reproduction - reproductive performance - performance - research - agricultural research - group housing
    Produceren zeugen in vaste groepen beter dan zeugen in wisselgroepen? Een belangrijke vraag voor varkenshouders die willen overschakelen naar groepshuisvesting. Het Praktijkcentrum Lelystad zoekt via een vergelijkende proef naar het antwoord.
    Biotechnology of reproduction and farm animals welfare
    Kruip, T.A.M. ; Reenen, C.G. van - \ 2002
    In: Animal welfare and animal health / Ellendorff, F., Moennig, V., Ladewig, J., Babiuk, L., Braunschweig : Bundesforschungsanstalt für Landwirtschaft (Landbauforschung Völkenrode Sonderheft 227) - ISBN 9783933140500 - p. 57 - 62.
    animal welfare - reproductive performance - biotechnology - animal breeding methods
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