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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    Optimising and Evaluating the Characteristics of a Multiple Antigen ELISA for Detection of Mycobacterium bovis Infection in a Badger Vaccine Field Trial
    Aznar, I. ; Frankena, K. ; More, S.J. ; Whelan, C. ; Martin, W. ; Gormley, E. ; Corner, L.A.L. ; Murphy, D. ; Jong, M.C.M. de - \ 2014
    PLoS ONE 9 (2014)7. - ISSN 1932-6203
    gamma-interferon assay - meles-meles - endobronchial inoculation - experimental tuberculosis - protective immunity - cattle herds - bcg - sensitivity - challenge - pathology
    A long-term research programme has been underway in Ireland to evaluate the usefulness of badger vaccination as part of the national bTB (bovine tuberculosis) control strategy. This culminated in a field trial which commenced in county Kilkenny in 2009 to determine the effects of badger vaccination on Mycobacterium bovis transmission in badgers under field conditions. In the present study, we sought to optimise the characteristics of a multiplex chemiluminescent assay for detection of M. bovis infection in live badgers. Our goal was to maximise specificity, and therefore statistical power, during evaluation of the badger vaccine trial data. In addition, we also aimed to explore the effects of vaccination on test characteristics. For the test optimisation, we ran a stepwise logistic regression with analytical weights on the converted Relative Light Units (RLU) obtained from testing blood samples from 215 badgers captured as part of culling operations by the national Department of Agriculture, Food and the Marine (DAFM). The optimised test was applied to two other datasets obtained from two captive badger studies (Study 1 and Study 2), and the sensitivity and specificity of the test was attained separately for vaccinated and non-vaccinated badgers. During optimisation, test sensitivity was maximised (30.77%), while retaining specificity at 99.99%. When the optimised test was then applied to the captive badger studies data, we observed that test characteristics did not vary greatly between vaccinated and non-vaccinated badgers. However, a different time lag between infection and a positive test result was observed in vaccinated and non-vaccinated badgers. We propose that the optimized multiplex immunoassay be used to analyse the vaccine trial data. In relation to the difference in the time lag observed for vaccinated and non-vaccinated badgers, we also present a strategy to enable the test to be used during trial evaluation.
    Onderzoek naar inheemse wilde fauna, verslag over 2013
    Tulden, P.W. van - \ 2014
    Lelystad : Central Veterinary Institute (Rapport / Central Veterinairy Institute 14/CVI0014) - 31
    fauna - wild - vogels - vissen - zoogdieren - toxicologie - pathologie - doodsoorzaken - monitoring - fauna - wildlife - birds - fishes - mammals - toxicology - pathology - causes of death - monitoring
    Met betrekking tot een aantal opgedragen Wettelijke Onderzoekstaken (WOT) treedt het Central Veterinairy Institute op als Nationaal Referentie Laboratorium (NRL) voor aangifteplichtige virale, parasitaire, protozoaire en bacteriële ziekten, TSE’s en antimicrobiële resistentie. Dit verslag geeft een overzicht van onderzoek aan de dieren, die opgestuurd zijn naar het CVT. Enkele cijfers: 137 inzendingen in het kader van het wettelijke wilde fauna onderzoek. Maar ook 188 kadavers, 6 levende watervogels en 27 monsters verdacht materiaal. De kadavers zijn te verdelen in 65 roofvogels, 70 watervogels, 13 overige vogels, 26 zoogdieren en 14 vissen. Hier kon van 115 van de 188 kadavers de doodsoorzaak worden achterhaald. De meest vastgestelde doodsoorzaken zijn trauma, vergiftiging, uitputting, afschot en botulisme, afhankelijk van de diercategorie.
    Vertical transmission of Rift Valley Fever Virus without detectable maternal viremia
    Antonis, A.F.G. ; Kortekaas, J.A. ; Kant-Eenbergen, H.C.M. ; Vloet, R.P.M. ; Vogel-Brink, A. ; Stockhofe, N. ; Moormann, R.J.M. - \ 2013
    Vector-Borne and Zoonotic Diseases 13 (2013)8. - ISSN 1530-3667 - p. 601 - 606.
    enzootic hepatitis - sheep - cattle - lambs - pathogenesis - pathology - vaccines - vectors - illness
    Rift Valley fever virus (RVFV) is a zoonotic bunyavirus that causes abortions in domesticated ruminants. Sheep breeds exotic to endemic areas are reportedly the most susceptible to RVFV infection. Within the scope of a risk assessment program of The Netherlands, we investigated the susceptibility of a native breed of gestating sheep to RVFV infection. Ewes were infected experimentally during the first, second, or third trimester of gestation. Mortality was high among ewes that developed viremia. Four of 11 inoculated ewes, however, did not develop detectable viremia nor clinical signs and did not seroconvert for immunoglobulin G (IgG) or IgM antibodies. Surprisingly, these ewes were found to contain viral RNA in maternal and fetal organs, and the presence of live virus in fetal organs was demonstrated by virus
    Epizootic of ovine congenital malformations associated with Schmallenberg virus infection
    Brom, R. van der; Luttikholt, S.J. ; Lievaart-Peterson, K. ; Peperkamp, N.H.M.T. ; Mars, M.H. ; Poel, W.H.M. van der; Vellema, P. - \ 2012
    Tijdschrift voor Diergeneeskunde 137 (2012)2. - ISSN 0040-7453 - p. 106 - 111.
    schapenhouderij - lammeren - lammerenziekten - misvormingen - veterinaire praktijk - schmallenbergvirus - virusziekten - orthobunyavirus - sheep farming - lambs - lamb diseases - malformations - veterinary practice - schmallenberg virus - viral diseases - orthobunyavirus - cache valley virus - akabane virus - bluetongue virus - small ruminants - newborn lambs - sheep - arthrogryposis - disease - pathology - fever
    Epizootic outbreaks of congenital malformations in sheep are rare and have, to the best of our knowledge, never been reported before in Europe. This paper describes relevant preliminary findings from the first epizootic outbreak of ovine congenital malformations in the Netherlands. Between 25 November and 20 December 2011, congenital malformations in newborn lambs on sheep farms throughout the country were reported to the Animal Health Service in Deventer. Subsequently, small ruminant veterinary specialists visited these farms and collected relevant information from farmers by means of questionnaires. The deformities varied from mild to severe, and ewes were reported to have given birth to both normal and deformed lambs; both male and female lambs were affected. Most of the affected lambs were delivered at term. Besides malformed and normal lambs, dummy lambs, unable to suckle, were born also on these farms. None of the ewes had shown clinical signs during gestation or at parturition. Dystocia was common, because of the lambs' deformities. Lambs were submitted for post-mortem examination, and samples of brain tissue were collected for virus detection. The main macroscopic findings included arthrogryposis, torticollis, scoliosis and kyphosis, brachygnathia inferior, and mild-to-marked hypoplasia of the cerebrum, cerebellum and spinal cord. Preliminary data from the first ten affected farms suggest that nutritional deficiencies, intoxication, and genetic factors are not likely to have caused the malformations. Preliminary diagnostic analyses of precolostral serum samples excluded border disease virus, bovine viral diarrhoea virus, and bluetongue virus. In December 2011, samples of brain tissue from 54 lambs were sent to the Central Veterinary Institute of Wageningen University Research, Lelystad. Real-time PCR detected the presence of a virus, provisionally named the Schmallenberg virus, in brain tissue from 22 of the 54 lambs, which originated from seven of eight farms that had submitted lambs for post-mortem examination. This Schmallenberg virus was first reported in Germany and seems to be related to the Shamonda, Aino, and Akabane viruses, all of which belong to the Simbu serogroup of the genus Orthobunyavirus of the family Bunyaviridae. These preliminary findings suggest that the Schmallenberg virus is the most likely cause of this epizootic of ovine congenital malformations, which is the first such outbreak reported in Europe
    Systemic Virus distribution and host responses in brain and intestine of chickens infected with low pathogenic and high pathogenic avian influenza virus
    Post, J. ; Burt, D.W. ; Cornelissen, J.B.W.J. ; Broks, V.C.M. ; Zoelen, D. van; Peeters, B.P.H. ; Rebel, J.M.J. - \ 2012
    Virology journal 9 (2012). - ISSN 1743-422X - 14 p.
    hemagglutinin cleavage site - membrane-fusion - pekin ducks - a viruses - h5n1 - pathology - pathobiology - replication - chemokines - antibodies
    Background: Avian influenza virus (AIV) is classified into two pathotypes, low pathogenic (LP) and high pathogenic ( HP), based on virulence in chickens. Differences in pathogenicity between HPAIV and LPAIV might eventually be related to specific characteristics of strains, tissue tropism and host responses. Methods: To study differences in disease development between HPAIV and LPAIV, we examined the first appearance and eventual load of viral RNA in multiple organs as well as host responses in brain and intestine of chickens infected with two closely related H7N1 HPAIV or LPAIV strains. Results: Both H7N1 HPAIV and LPAIV spread systemically in chickens after a combined intranasal/intratracheal inoculation. In brain, large differences in viral RNA load and host gene expression were found between H7N1 HPAIV and LPAIV infected chickens. Chicken embryo brain cell culture studies revealed that both HPAIV and LPAIV could infect cultivated embryonic brain cells, but in accordance with the absence of the necessary proteases, replication of LPAIV was limited. Furthermore, TUNEL assay indicated apoptosis in brain of HPAIV infected chickens only. In intestine, where endoproteases that cleave HA of LPAIV are available, we found minimal differences in the amount of viral RNA and a large overlap in the transcriptional responses between HPAIV and LPAIV infected chickens. Interestingly, brain and ileum differed clearly in the cellular pathways that were regulated upon an AI infection. Conclusions: Although both H7N1 HPAIV and LPAIV RNA was detected in a broad range of tissues beyond the respiratory and gastrointestinal tract, our observations indicate that differences in pathogenicity and mortality between HPAIV and LPAIV could originate from differences in virus replication and the resulting host responses in vital organs like the brain.
    Bruinvisstrandingen in Nederland in 2006: achtergronden, leeftijdsverdeling, sexratio, voedselkeuze en mogelijke oorzaken
    Leopold, M.F. ; Camphuysen, C.J. - \ 2006
    IJmuiden : IMARES (NIOZ rapport 2006-5) - 136
    phocoenidae - pathologie - doodsoorzaken - noordzee - phocoenidae - pathology - causes of death - north sea
    Bruinvissen komen in steeds grotere aantallen voor in de Nederlandse (kust)wateren. In de periode 1960␂ 1985 was de bruinvis vrijwel uitgestorven in Nederland, maar de soort heeft een spectaculaire comeback gemaakt. Terwijl het aantal waarnemingen sterk toenam werd er ook een toename gevonden in het aantal dieren dat dood op de kust aanspoelde. In september 2006 werden 64 bruinvissen onderzocht die eerder dat jaar dood op de Nederlandse kust waren aangespoeld
    Diergezondheid en management
    Hanekamp, W.J.A. ; Ouweltjes, W. ; Schepers, A.J. ; Smolders, E.A.A. - \ 1994
    Lelystad : Proefstation voor de Rundveehouderij, Schapenhouderij enPaardenhouderij (Publikatie / Proefstation voor de Rundveehouderij, Schapenhouderij en Paardenhouderij 92) - 46
    diergeneeskunde - pathologie - bedrijfsresultaten in de landbouw - rentabiliteit - bedrijfsvoering - methodologie - onderzoek - veterinary science - pathology - farm results - profitability - management - methodology - research
    Het doel van dit managementonderzoek is te komen tot betere hulpmiddelen voor de melkveehouder voor de ondersteuning van het management op zijn bedrijf. Voor dit onderzoek kan onder andere gebruik gemaakt worden van een uitgebreide dierregis-tratie opeen negental proefbedrijven vanaf 1988.
    De invloed van gezondheidsstoornissen bij gespeende biggen op de mesterijresultaten en slachtkwaliteit
    Kloosterman, A.A.M. ; Baeten, P.P.E. ; Huiskes, J.H. - \ 1992
    Rosmalen : Proefstation voor de Varkenshouderij (Proefverslag / Proefstation voor de Varkenshouderij P1.80) - 27
    karkassamenstelling - karkaskwaliteit - ontwikkeling - groei - pathologie - biggen - slacht - diergeneeskunde - carcass composition - carcass quality - development - growth - pathology - piglets - slaughter - veterinary science
    Slachtbevindingen laten schade voor varkenshouder en slachterij zien
    Huiskes, J. - \ 1991
    Praktijkonderzoek varkenshouderij 5 (1991)2. - ISSN 1382-0346 - p. 15 - 17.
    varkens - diergeneeskunde - karkassamenstelling - productiviteit - rentabiliteit - dierhouderij - pathologie - slachthuizen - vlees - verpakken - bedrijfsresultaten in de landbouw - pigs - veterinary science - carcass composition - productivity - profitability - animal husbandry - pathology - abattoirs - meat - packing - farm results
    In het proefproject Integrale Keten Beheersing (IKB) bij vleesvarkens is onderzoek uitgevoerd om inzicht te verkrijgen in de economische betekenis van twaalf slachtbevindingen voor de mesterijfase en de slachterijfase. Het grootste deel van de financiële schade wordt veroorzaakt door de slachtbevindingen, borstvliesontsteking en longafwijkingen.
    Cluster gezondheidszorg: basis voor een betere gezondheidszorg op het varkensbedrijf
    Koning, R. de; Ven, E.P.H.E. van de - \ 1989
    Praktijkonderzoek varkenshouderij 3 (1989)6. - ISSN 1382-0346 - p. 20 - 22.
    communicatie - agrarische bedrijfsvoering - informatie - informatiesystemen - bedrijfsvoering - pathologie - varkens - diergeneeskunde - communication - farm management - information - information systems - management - pathology - pigs - veterinary science
    Het Informatiemodel Varkenshouderij wordt in gedeelten, zogenaamde clusters, uitgewerkt door onder andere het proefstation voor de varkenshouderij en de takorganisatie SIVA. De cluster gezondheidszorg is in september gereed gekomen.
    Impact of early pregnancy on prenatal development in the pig
    Lende, T. van der - \ 1989
    Agricultural University. Promotor(en): A. Hoogerbrugge. - S.l. : Van der Lende - 152
    vruchtbaarheid - infertiliteit - bevruchting - varkens - diergeneeskunde - embryologie - ontogenie - zoölogie - vrouwelijke genitaliën - obstetrie - zwangerschap - pathologie - fertility - infertility - fertilization - pigs - veterinary science - embryology - ontogeny - zoology - female genitalia - obstetrics - pregnancy - pathology

    In the present study aspects of the impact of early pregnancy on the average prenatal development per litter and on the within-litter weight distribution at birth have been investigated. The aims of the present study are given in the introduction (chapter 1). A brief review of the literature concerning the chronology of early pregnancy and embryonic mortality in the pig is given in chapter 2.

    In chapter 3 an experiment is described in which it was attempted to affect the development and functioning of the uterus structurally in order to obtain a model in which the role of the uterus and its secretion

    'products as determinants of embryonic mortality and/or embryonic development could be studied. The possibility to affect the functional integrity of the uterus by means of a severe growth retardation during the first 80 days of life, i.e. during the period in which the uterine glands differentiate, was investigated. A group of female piglets were weaned within 24 hours after birth and either fed unrestricted (n=35) or restricted (n=34). The restricted fed piglets were allowed to grow at a rate of approximately 50% of that of their unrestricted littermates. This contrast was maintained until day 80 after birth. Another group of piglets (control group, n=38) were normally weaned at an age of 35 days and subsequently fed unrestricted until day 80. From day 35 onwards all piglets were kept under the same conditions and from day 80 onwards they were also treated the same. A representative sample from each of the three groups (unrestricted fed (n=8), restricted fed (n=8) and control (n=10)) were slaughtered at an age of 80 days to study the histomorphology of their uterus. The remaining gilts which reached puberty and became pregnant (n=50) were slaughtered on either day 34, 35 or 36 of first pregnancy. The uterine and conceptus development were subsequently studied.

    At day 80 the average weight of restricted fed piglets was 45% of that of unrestricted fed piglets and 48% of that of control piglets. Although the averages for uterine length and weight, thickness of the myometrium and endometrium and the relative glandular surface area were all lower in the restricted fed than in both other groups, only the difference in thickness of the myometrium between the restricted fed group and control group was significant. All differences were merely due to differences in bodyweight. No negative effects were seen on ovulation rate, number of embryos, embryonic mortality rate, uterine length and weight or any of the parameters for conceptus development. This indicates that the functional integrity of the uterus is not affected by a severe growth retardation during the first 80 days of life.

    With the data collected for the gilts which were slaughtered on day 35 of pregnancy in this experiment (n=31) and data collected for another group of Dutch Landrace gilts which were also slaughtered on day 35 of pregnancy (n=40), the relationship between conceptus development and embryonic mortality was studied. The results of this study are described in chapter 4. For purposes of interpretation of the results, especially concerning the development of the placentae, relevant uterine parameters were also considered. The results indicate that the embryonic weight and length significantly decrease with an increasing embryonic mortality rate, whereas the placental weight and length significantly increase with an increasing embryonic mortality rate. Statistical analyses have shown that this decrease in embryonic development with an increasing embryonic mortality rate was not due to the concomitant increase in placental development. After correction for differences in number of embryos, these relationships (except for placental length) were no longer significant, indicating that embryonic mortality is related to conceptus development through its relationship with number of embryos. It was concluded that factors that caused a high embryonic mortality - and thus small litters - also caused a low embryonic weight and length. From the fact that the uterine length available per embryo significantly increased with an increasing embryonic mortality, even after correction for the number of embryos, it was concluded that the relationship of embryonic mortality with placental development might be due to the effect that embryos which died had on the uterine length before their death.

    To study whether the accelerated growth of the placentae in gilts with a high embryonic mortality rate will be beneficial for the foetal development until birth, the relationship between foetal development and the prenatal mortality rate was studied. The results of this study for which 195 pregnant Dutch Landrace gilts were slaughtered between day 35 and day 112 of pregnancy, are described in chapter 5. From these results it was clear that the weight gain of foetuses between day 35 and day 100 of pregnancy was higher within gilts with a high prenatal mortality rate than within gilts with a low prenatal mortality rate. There were also marked differences between these two groups for placental development during this period. Within the group of gilts with a high prenatal mortality rate the placental weight and length increased until day 95 of pregnancy, to decrease thereafter. Within the group of gilts with a low prenatal mortality rate it increased until day 65, remained fairly constant until day 95, to increase rapidly thereafter. Although the prenatal mortality rate during the early foetal stage is most probably still a good estimator of the embryonic mortality rate, towards the end of pregnancy this is almost certainly no longer the case. The present study therefore does not allow decisive conclusions as to the relationship between embryonic mortality rate and the average birthweight.

    In chapter 4 and 5 the emphasis has been on the variation in prenatal development between litters. In chapter 6 and 7 one aspect of differences in prenatal development within litters (the within-litter weight distribution) has been studied. Although it is generally assumed that the within-litter weight distribution is normal (Gaussian), evidence has been provided for the fact that in approximately one-third of litters the distribution is abnormal in a sense that two subpopulations can be identified within these litters. On the other hand there is an accumulation of indications that within-litter variation in embryonic developmental stage can occur very early in pregnancy and that this variation is reduced before or shortly after the time of maternal recognition of pregnancy (day 11) through selective mortality of the less developed embryos. The results described in chapter 6 confirms the fact that the within-litter weight distribution is abnormal in 33% of all litters studied (466 foetal litters and 915 litters at term). On the basis of the within-litter weight distribution 5 littertypes were defined: normal litters (one normal distribution), litters with one or two runts (two discrete subpopulations: one main distribution and one or two growth retarded outliers), litters with left-hand individuals (two discrete subpopulations, the left-hand distribution numerically smaller than or equal to the right-hand distribution and both larger than 2), litters with right-hand individuals (two discrete subpopulations, the right hand distribution numerically smaller than the left-hand distribution and both larger than 2) and litters with one or two giants (two discrete subpopulations: one main distribution and 1 or 2 growth accelerated outliers). The results strongly suggest that the within-litter weight distribution as found at term has been established by the end of the embryonic stage (day 35) of pregnancy, at least in the majority of litters. The average embryonic mortality rate differed between littertypes. The lowest mortality rate was found for the litters with lefthand individuals, the highest for litters with giants.

    The preweaning death risk and preweaning growth rate of piglets in relation to the within-litter weight distribution of the litter in which they were born and suckled were subsequently studied. The results, based on data for 819 litters, are described in chapter 7. The preweaning death risk of piglets from litters with two discrete subpopulations was not higher than that for piglets from litters with a normal within-litter weight distribution. In all 5 littertypes the death risk was similarly dependent on birthweight, litter size and within-litter variation in birthweight. The average preweaning growth rate per litter differed between littertypes but was entirely due to differences in average litter size at birth. Within each of the 4 littertypes with two discrete subpopulations the average growth rate of the piglettype with the lower average birthweight was always less than that for the piglettype with the higher average birthweight. Within litters with runts and left-hand individuals this remained the case even after correction for birthweight, indicating that the growth rate of runts and left-hand individuals is less than would be expected on the basis of their birthweights.

    A general discussion of the results and the conclusions are given in chapter 8. The results of the present study allows the following conclusions:
    1. The functional integrity of the uterus of gilts as measured by its ability to support the survival and normal development of embryos, can not be adversely affected by a regular, severe growth retardation during the first 80 days of life, i.e. during the period of differentiation of the uterine glands.
    2. Day 35 embryos in gilts with a low embryonic mortality rate (the larger litters) are better developed than day 35 embryos in gilts with a high embryonic mortality rate (the smaller litters), indicating that factors that are favourable for embryonic survival are also favourable for embryonic development or are associated with factors that are favourable for embryonic development.
    3. The placentae of day 35 embryos in gilts with a high embryonic mortality rate (the smaller litters) are better developed than the placentae of day 35 embryos in gilts with a low embryonic mortality rate (the larger litters). As a consequence the foetuses in gilts with a high embryonic mortality will grow faster than foetuses in gilts with a low embryonic mortality rate.
    4. The within-litter weight distribution is normal (Gaussian) in approximately 67% of all litters; within the remaining litters two discrete subpopulations of variable size can be identified.
    5. The within-litter weight distribution at birth is established at the end of the embryonic stage of pregnancy (day 35) and is related to the embryonic mortality rate.
    6. The within-litter weight distribution at birth is neither an important determinant of the within-litter variation in birthweight, nor an important determinant of the preweaning death risk of liveborn piglets.

    Vitamin E affects viability immune response of poultry.
    Boushy, A.R. El - \ 1988
    Feedstuffs 60 (1988)44. - ISSN 0014-9624 - p. 20 - 24, 26.
    kippen - pathologie - pluimvee - tocoferolen - diergeneeskunde - vitamine e - vitaminetoevoegingen - fowls - pathology - poultry - tocopherols - veterinary science - vitamin e - vitamin supplements
    Belang van vitamine E voor pluimvee wordt beschreven
    Biology of stress in farm animals: an integrative approach.
    Wiepkema, P.R. ; Adrichem, P.W.M. van - \ 1987
    Dordrecht [etc.] : Nijhoff - ISBN 9780898388954 - 198
    vee - stress - stressreactie - endocrinologie - immunologie - pathologie - neurologie - diergedrag - dierenwelzijn - dierfysiologie - livestock - stress - stress response - endocrinology - immunology - pathology - neurology - animal behaviour - animal welfare - animal physiology
    Embryonale sterfte bij het varken: incidentie en mogelijkheden ter preventie.
    Lende, T. van der; Hazeleger, W. - \ 1987
    Tijdschrift voor Diergeneeskunde 112 (1987). - ISSN 0040-7453 - p. 1106 - 1113.
    beren (varkens) - embryotransplantatie - foetus - eiceltransplantatie - pathologie - varkens - zwangerschap - diergeneeskunde - boars - embryo transfer - fetus - ova transfer - pathology - pigs - pregnancy - veterinary science
    Dystocia in dairy cattle breeding [:with special attention to sire evaluation for categorical traits]
    Meijering, A. - \ 1986
    Landbouwhogeschool Wageningen. Promotor(en): R.D. Politiek; E.W. Brascamp. - Wageningen : Meijering - 179
    dierveredeling - geboorte - melkvee - melkveehouderij - verbetering - partus - pathologie - weerstand - diergeneeskunde - animal breeding - birth - dairy cattle - dairy farming - improvement - parturition - pathology - resistance - veterinary science
    Field data recorded in the early seventies showed that dystocia (calving difficulty) in the main Dutch cattle breeds occurred at a rate of 15-17% in heifers and 5-6% in cows. Corresponding stillbirth rates were 9-12% and 2.5-3.5% respectively. In the sixties and seventies many research papers on dystocia and stillbirth appeared which dealt with frequencies in various breeds and breed crosses, causes, associated factors, economic consequences and factors with systematic impact. These papers are reviewed in chapter 1. Important conclusions can be summarized as follows.

    1. Dystocia is a major cause of stillbirth: 40 to 60% of the stillbirth cases encountered in field data are associated with dystocia. Additional negative consequences of dystocia are increased labour and veterinary costs, reduced fertility and milk yield, and an increased culling rate.

    2. First-calf heifers and older cows differ both in frequency and in cause of dystocia. The frequency of calving difficulty in eifers is generally three to four times as high as in cows. In heifers, the most frequent cause of dystocia is feto-pelvic-incompatibility, i.e. a disproportion between the size of the calf and the pelvic dimensions of its dam. Deviations in the presentation of the calf account for a second substantial part. In cows, feto-pelvic- incompatibility is encountered less frequently, whereas other causes such as weak labour, uterine torsion and insufficient cervical dilation are rela tively more important.

    3. Within parity, the probability of dystocia is positively related, i.e. increases, with the weight and dimensions of the calf at birth. The (phenotypic) relationships show a threshold character, i.e. the probability of dystocia increases strongly when the size of the calf exceeds a certain threshold value. The probability of dystocia is positively related with gestation length as well, probably mediated by calf size. With respect to the dimensions of the pelvic inlet of the dam a negative relationship is found. The size of the calf and the dimensions of the dam's pelvic inlet are the basic elements in feto-pelvic-incompatibility.

    4. Apart from parity of the dam, factors with systematic influence on the frequency of calving difficulty are sex of calf and season of calving. In male calves the frequency is about twice as high as in females which is mainly due to the larger average size of the males. In the North-Western part of Europe dystocia tends to be more frequent in autumn and early winter than in spring and summer. This seasonal pattern is often, but not always, found to be associated with a seasonal fluctuation in birth weight.

    5. Dystocia, stillbirth, as well as the associated calving traits birth weight and gestation length, are influenced by the genotype of both the calf and its dam, which results in a complicated genetic model. With a view to sire selection, the influence of the genotype of the calf is generally referred to as sire-of-calf effect, direct genetic effect or mate effect. Similary, the influence of the genotype of the dam is referred to as maternal-grandsire effect or indirect genetic effect. The mode of action of the direct genetic effect is supposed to be relatively simple: the sire transfers genes to the calf which are expressed in the calf phenotype (e.g. size, gestation length) which may affect the ease of birth. The maternal grandsire is supposed to act upon calving traits in a more complicated way. First, the maternal-grandsire effect contains a direct genetic component since the sire of the dam also transfers genes to the calf. This part of the maternal-grandsire effect is similar to the sire-of- calf effect but half of the size. Besides, the maternal grandsire may in fluence calving traits by transferring genes to the dam which actual ly find expression in the dam, for instance in the pelvic dimensions or by means of a maternal effect on the size of the calf. This is referred to as the maternal genetic component. The direct and mater nal genetic component are suspected to interact. Estimates of rele vant parameters are summarized in tables III to VI of chapter 1.

    6. Difficulties are encountered in the genetic-statistical analysis of data on ease of calving and stillbirth because of their categorical nature. At least in theory, the non-normality, the location dependent variance and the non-additivity of-effects involved reduce the value of the usual estimation and prediction techniques based on the linear model and on normality of traits.

    In the sixties and seventies AI-organisations in the Netherlands gradually started to apply the results from the research on calving traits, those on the effect of parity and the sire-of-calf effect in particular, by introducing a so-called heifer-bull-programme. This involves the testing of young bulls for direct genetic effect on calving traits and the recommendation of low-risk bulls with respect to dystocia and stillbirth for heifer matings. At that time, the data collection procedure was not uniform over AI-organisations, whilst the method of sire evaluation was not optimized. At the end of the seventies the research project which underlies this thesis was started, with two main objectives:

    1. Optimization of the heifer-bull-programme including data collection and sire evaluation.

    2. Examination of alternative sire-selection strategies to reduce dystocia, with emphasis on the impact of maternal genetic effects and direct maternal-interaction.

    Sire evaluation for categorical traits

    The optimization of data collection within the framework of the heiferbull-programme is no subject-matter of this thesis, but one of the main results, a mark-sense card for birth recording which is used nation-wide now, is shown as figure 1 in chapter 4. In the optimization of sire evaluation, emphasis was laid on a comparison between the method of Best Linear Unbiased Prediction (BLUP), which has optimal properties with normally distributed data, and a pseudo- Bayesian nonlinear method of sire evaluation for categorical variates based on the "threshold', concept, when applied to binary and ordered tetrachotomous reponses.

    Chapter 2 refers to a comparison of these two methods with simulated data with a family structure consisting of half-sib groups of equal or unequal size. Simulations were done at varying levels of heritability and incidences of the binary trait. The methods were compared for their ability to elicit responses to truncation selection. The nonlinear procedure, which is theoretically more appealing, proved to be superior in a mixed model setting when the responses were binary, the layout was highly unbalanced, heritability was moderate to high and the incidence was below 25%. When a one-way model was tenable or when responses were tetrachotomous, the results by both methods were very similar.

    In a similar simulation study, it was examined whether the incorporation of heteroscedastic residual variance into the BLUP-model would improve the sire-ranking ability of this method with categorical variates (chapter 3). Such an "adjustment" was proposed in the literature. The results indicated however that the ability of BLUP to rank sires correctly for categorical traits is impaired by adjustments of this kind, particulary when responses are binary, in spite of a reduction in apparent prediction error variance. This is consistent with deductions from the theory of threshold models.

    In a third study (chapter 4) BLUP, with homogeneous residual variance, and the nonlinear method were compared in estimating genetic merits for ease of calving and stillbirth under field conditions, i.e. with a data sample from the birth recording programme in the Netherlands. Since only minor differences in sire ranking were observed between the two methods, it is concluded that there is no clear advantage in applying the nonlinear prcedure, which entails more complicated and time consuming computations than BLUP, in sire evaluation for dystocia and stillbirth.

    The results of these studies lead to the conclusion that BLUP with homogeneous residual variance, which is a standard method of sire evaluation for dairy traits in many countries, is fairly robust against the departures from normality and linearity arising with categorical data. Because of the computational expenses involved in the nonlinear procedure, particulary with large data sets, an appropriate BLUP-model which should at least correct for parity, sex of calf, herd and season of calving is advised for the evaluation of sires for dystocia and stillbirth in the Netherlands.

    Sire selection for dystocia

    Sire selection for direct genetic effect on dystocia may not be very appealing under the Dutch market conditions because dystocia is very highly cor related, in the genetic sense, with birth weight (r g ≈0.9) as shown in chapter 4. A reduction in level of dystocia by this type of selection would almost inevitably entail a reduction in birth weight which will lower the proceeds from the sale of young calves from the dairy farm. Since maternal effects are assumed to be involved in ease of birth, selection for traits contributing to maternal calving performance might be an alternative. With the exception of the pelvic inlet dimensions, which are difficult to measure and hence unsuitable for al large scale progeny test, such traits had not been identified. Chapter 5 refers to a study into the phenotypic association between ease of calving and a number of, mainly morphologic, dam traits in Holstein, Dutch Red and White and Dutch Friesian heifers. However, the only factor clearly associated with ease of calving was the size of the calf.

    Since the attempt to identify dam traits with significant effect on calving performance failed, alternatives left apart from the heifer- bull-programme, are selection for direct genetic effect, with the disadvantage discussed, or selection for maternal-grandsire effect. Because of the suspected negative covariance between the direct and maternal genetic effects, it was felt necessary to examine the sign and the size of the covariance between the direct genetic effect and the maternal-grandsire effect. This necessity was underlined by a reluctancy among herdsmen to use the low-risk bulls identified in the heifer-bull-programme because they suspected that these bulls would sire small calves, which develop into small heifers and which run an increased risk of dystocia. In chapter 6 this hypothesis is examined in a two-way sireselection trial with purebred Holstein, Dutch Red and White and Dutch Friesian cattle. Although the results were not entirely consistent over breeds, this study yielded additional evidence that direct and maternal-grandsire merits for ease of birth as well as for birth weight and gestation length are correlated positively. It was conjectured that the maternal- grandsire effect on ease of birth is dominated by direct inheritance of calf size. This conclusion implies that selection of sires for ease of birth of their progeny as calves is expected to yield a favourable response with respect to the ease of calving of their daughters and vice versa.

    Selection programmes

    In the final chapter, the monetary (discounted) returns from three schemes of breeding bull selection for calving traits (score for calving ease, birth weight, gestation length), viz. identification of lowrisk bulls for heifer matings among breeding bulls selected for dairy traits, selection on direct genetic merit for calving traits in addition to selection for dairy traits and selection on maternal-grandsire merit for calving traits in addition to selection for dairy traits are estimated for several calf price levels and incidences of dystocia. The first scheme, i.e. the heifer-bull-programme, proved to increase the returns from a breeding programme in dairy cattle, particularly when the incidence of dystocia or the calf price is high. Within such a scheme sire evaluation for birth weight and gestation length in addition to the evaluation for a score for calving ease contributes only marginally to the accuracy of low-risk-bull identification, at least when the latter is based on about 200 progeny per sire. Selection indices for direct genetic or maternal-grandsire effects on calving traits reduced the incidence of dystocia only at low calf prices (upto about Dfl 5.00 per kg). In the normal calf price range in the Netherlands (Dfl 7.50 - Dfl 15.00 per kg) either type of selection, if advisable at all, should be for an increase in birth weight in spite of a corresponding rise in incidence of dystocia. This is due to the highly positive genetic correlation between dystocia and birth weight. Because of a reduced intensity of selection for dairy traits, the impact of additional selection for birth weight on the total returns from the selection of breeding bulls in dairy cattle is either negative, or only marginally positive however. Consequently, the heifer-bull-programme is the most attractive breeding strategy to reduce dystocia.

    Proefproject geboorteregistratie
    Meijering, A. ; Eldik, P. van - \ 1981
    Zeist : IVO (Rapport / Instituut voor Veeteeltkundig Onderzoek "Schoonoord" no. B-165)
    geboorte - rundvee - nederland - partus - pathologie - diergeneeskunde - birth - cattle - netherlands - parturition - pathology - veterinary science
    Aflamproblemen bij ooien van verschillende paringstypen
    Visscher, A.H. ; Lohuyzen, M.G. van - \ 1981
    Zeist : I.V.O. (Rapport / Instituut voor Veeteeltkundig Onderzoek "Schoonoord" no. B-186) - 57
    geboorte - partus - pathologie - schapen - diergeneeskunde - birth - parturition - pathology - sheep - veterinary science
    Het seizoen van afkalven van rundvee
    Anonymous, - \ 1977
    Wageningen : Pudoc (Literatuurlijst / Centrum voor landbouwpublikaties en landbouwdocumentatie no. 4074)
    bibliografieën - geboorte - rundvee - pathologie - zwangerschap - diergeneeskunde - bibliographies - birth - cattle - pathology - pregnancy - veterinary science
    Induction of bovine parturition with flumentasone and estrogens and its effect on the incidence of retained placenta and milkfever
    Osinga, A. ; Hazeleger, W. ; Bootsma, A. ; Peynenburg, T. ; Boer, D.J. den; Dijke, J.J. van - \ 1977
    Wageningen : L.H. - 8
    geboorte - rundvee - diergeneeskunde - melkziekte - pathologie - partus - afwijkingen - aangeboren afwijkingen - birth - cattle - veterinary science - parturient paresis - pathology - parturition - abnormalities - congenital abnormalities
    Voeding en ziekten bij vogels
    Anonymous, - \ 1975
    Wageningen : [s.n.] (Literatuurlijst / Centrum voor landbouwpublikaties en documentatie no. 3816)
    dierziekten - diervoedering - bibliografieën - voer - kippen - jachtdieren - jachtvogels - bedrijfsvoering - pathologie - plagen - pluimvee - diergeneeskunde - animal diseases - animal feeding - bibliographies - feeds - fowls - game animals - game birds - management - pathology - pests - poultry - veterinary science
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