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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.

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    Prolonged parturition and impaired placenta expulsion increase the risk of postpartum metritis and delay uterine involution in sows
    Björkman, S. ; Oliviero, C. ; Kauffold, J. ; Soede, N.M. ; Peltoniemi, O. - \ 2018
    Theriogenology 106 (2018). - ISSN 0093-691X - p. 87 - 92.
    parturition - oxytocin - Retained placentae - Postpartum metritis - Uterine involution
    It was hypothesized that prolonged parturition and impaired placenta expulsion increase the risk of postpartum metritis and delay uterine involution. At parturition, for 99 Yorkshire x Large White sows (parity 2–5), we determined the number of liveborn (NLP; 14.8 ± 3.4) and stillborn piglets (NSP; 1.1 ± 1.1), farrowing duration (FAR, time between first and last piglet; 333 ± 249 min), placenta expulsion duration (PLA, time between first and last placental part; 292 ± 241 min) and number of expelled placental parts (PART; 3.0 ± 1.0). FAR was categorized as ‘normal’ (<300 min; n = 44/99) or ‘prolonged’ (>300 min; n = 55/99). The relative PLA (rPLA; (PLA * 100)/FAR; 76 ± 101%) and the relative PART (rPART; (PART * 100)/(NLP + NSP); 22 ± 8%) were calculated and placenta expulsion was categorized as ‘normal’ (rPLA and rPART > 10%; n = 93/99) or ‘impaired’ (relPLA and relPART < 10%; n = 6/99). We also recorded whether manual palpation occurred (Yes/No) and/or oxytocin was used (Yes/No). After parturition, an ultrasound examination of the uterus was performed once for each sow between the 2nd and 7th day postpartum and the uterine size (mean sectional area of three to five uterine cross-sections) and intrauterine fluid accumulation (Yes/No) were recorded. Uterine size was categorized as ‘normal’ (n = 55/99) or ‘enlarged’ (n = 44/99) and used as an indicator of delayed uterine involution. Intrauterine fluid was used as an indicator of metritis. Prolonged FAR (35/54, 2.0 ± 0.5, 13.1, 7.6; n/N, β ± SE, Wald χ2, Odds; P = 0.001), manual palpation (12/17, 1.5 ± 0.7, 4.4, 4.3; P = 0.036), oxytocin administration (18/31, - 1.5 ± 0.7, 4.7, 0.2, P = 0.040) and NSP ≥ 2 (15/21, 1.4 ± 0.7, 3.8, 3.9; P = 0.052) were associated with increased uterine size (n = 44/99) and NSP ≥ 2 (7/21, 2.6 ± 0.9, 8.7, 13.7; P = 0.003), manual palpation (10/17, 1.8 ± 0.8, 5.0, 6.0; P = 0.025), prolonged FAR (13/15, 1.7 ± 0.8, 4.3, 5.7; P = 0.039) and impaired PLA (4/6, 3.3 ± 1.7, 4.0, 26.9; P = 0.044) with intrauterine fluid accumulation (n = 15/99). The results confirm the hypothesis, indicating that prolonged parturition and impaired placenta expulsion increased the risk for postpartum metritis. Stillborn piglets and manual palpation were also identified as risk factors. Postpartum metritis delays uterine involution whereas the use of exogenous oxytocin supports it.
    Control of Pig Reproduction IX
    Rodriguez-Martinez, H. ; Soede, N.M. ; Flowers, W.L. - \ 2013
    Leicestershire, United Kingdom : Context Products Ltd (Society of Reproduction and Fertility volume 68) - ISBN 9781899043484 - 345
    varkens - geslachtelijke voortplanting - gameten - embryo's - kunstmatige inseminatie - embryotransplantatie - zwangerschap - partus - pasgeborenen - biggen - overleving - biotechnologie - metabolomica - eiwitexpressieanalyse - kunstmatige selectie - pigs - sexual reproduction - gametes - embryos - artificial insemination - embryo transfer - pregnancy - parturition - neonates - piglets - survival - biotechnology - metabolomics - proteomics - artificial selection
    Acid-base balance of umbilical artery blood of liveborn piglets at birth and its relation with factors affecting delivery of individual piglets
    Dijk, A.D.J. van; Lende, T. van der; Taverna, M.A. - \ 2006
    Theriogenology 66 (2006)8. - ISSN 0093-691X - p. 1824 - 1833.
    newborn piglets - perinatal mortality - parturition - viability - gas - pig - asphyxia - analyzer - ph - stillbirth
    In the limited number of studies that reported on the relation between factors affecting birth of individual piglets and acid-base balance values at birth, predominantly simple correlation coefficients have been used. The aim of the present study was to analyse the relation between factors affecting delivery of individual liveborn piglets and acid-base balance values (pH, P-CO2, HCO3- and BEecf) at birth. In total 201 piglets originating from 44 litters were used for the collection of blood samples from the umbilical artery immediately after birth, preferably in the period of apnea. Blood samples were analysed with the iStat (R) Portable Clinical Analyser. Significantly lower pH, HCO3-, BEecf and significantly higher P-CO2 levels were found in posteriorly presented piglets, independently of the condition of the umbilical cord, birth weight and cumulative birth interval/rank. Independently of presentation, birth weight and rank, piglets born with ruptured umbilical cords showed significantly lower pH values. Next to that, increasing birth weights resulted in increasing HCO3- and BEecf values at birth, independently of presentation, condition of the umbilical cord and cumulative birth interval/rank. Both an increase in cumulative birth interval and in rank was associated with a significant decrease of pH, HCO3-, BEecf and increase of P-CO2 levels in umbilical cord blood at birth. Together these results demonstrate for the first time that a clear relation exists between (factors affecting) the progress of delivery and acid-base balance values in a polytocous species like the pig. (c) 2006 Elsevier Inc. All rights reserved.
    Slow growth of a translocated beaver population partly due to a climatic shift in food quality
    Nolet, B.A. ; Broftova, L. ; Heitkönig, I.M.A. ; Kostkan, V. ; Vorel, A. - \ 2005
    Oikos 111 (2005)3. - ISSN 0030-1299 - p. 632 - 640.
    castor-fiber - synchrony - reproduction - phenology - parturition - responses - caribou - birth - tits
    In temperate regions climate change has led to advances in plant phenology which may disrupt the synchrony between food availability and reproductive requirements of higher trophic levels. Because leaf quality generally drops with leaf maturation, for herbivorous animals a stoichiometric effect of climate change may be of greater importance than a shift in food quantity. We hypothesized that such a climate-related stoichiometric effect caused the low reproductive success of a beaver Castor fiber population that was translocated westward in Europe at the time of a rapid increase in spring temperatures. The staple food of these beavers was willow Salix spp. In 2003 willow bud burst occurred approximately one month earlier at the release site than at the site of origin. After bud burst, leaf quality, measured as nitrogen and phosphorus concentration, decreased in the course of spring in a predictable manner with accumulated degree-days. Nitrogen and phosphorus concentrations calculated from accumulated degree-days were, at a given date, around 20% lower at the release site during the 15 years after the translocation than at the site of origin during the 15 years prior to the translocation. Previous work had identified phosphorus as a likely limiting resource for beaver reproduction, and in most post-translocation years phosphorus concentrations at the release site were below the required level towards the end of gestation. In addition to an increase over time, annual reproductive rate of the translocated beavers was highest in cold springs. We conclude that it was initially low due to a combination of low food quality and factors not related to climate.
    Changes in the feed intake, pH and osmolality of rumen fluid, and the position of the abomasum of eight dairy cows during a diet-induced left displacement of the abomasum
    Winden, S.C.L. van; Brattinga, C.R. ; Muller, K.E. ; Schonewille, J.T. ; Noordhuizen, J.P.T.M. ; Beynen, A.C. - \ 2004
    Veterinary Record 154 (2004)16. - ISSN 0042-4900 - p. 501 - 504.
    metabolic-disorders - risk-factors - cattle - parturition - milk
    During the last six weeks of the dry period, eight Holstein-Friesian cows were fed a restricted amount of grass silage; after calving, a mixture of maize silage and concentrates was offered in a feeding regimen designed to induce a displacement of the abomasum. In the first month after calving, the cows were monitored for the following variables: feed intake and composition, milk production, the position of the abomasum, and the pH and osmolality of the rumen contents. In five of the eight cows, a left displacement of the abomasum occurred between four and 21 days after calving in the absence of other diseases. The displacement was temporary, lasting between five and 36 consecutive hours and one or two days in two of the cows (floaters), and for three or more days in the other three. Before these three cows developed the displacement, their abomasum was 4.3 to 7.9 cm higher, its contents had a higher mean osmolality (+19.2 mosmol/kg), and the ratio of roughage to concentrates in their feed was lower (-0-87) than in the three cows that did not develop clinical signs of a displaced abomasum. There were no significant differences in these variables between the floaters and the healthy cows
    Physiology and genetics of leptin in periparturient dairy cows
    Liefers, S.C. - \ 2004
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Tette van der Lende; Roel Veerkamp. - [S.l.] : S.n. - ISBN 9789058089984 - 135
    melkkoeien - melkvee - hormonen - partus - dierfysiologie - genetica - vruchtbaarheid - melkresultaten - genetische polymorfie - genen - mutaties - selectief fokken - dairy cows - dairy cattle - hormones - parturition - animal physiology - genetics - fertility - dairy performance - genetic polymorphism - genes - mutations - selective breeding
    In dairy cattle, the increase in milk yield has been accompanied by a decrease in fertility and a more negative energy balance. As the hormone leptin is involved in regulation of nutritional status and reproductive function (Chapter 2) this is an interesting protein to investigate during the periparturient period in dairy cattle when many changes take place both in energy metabolism and reproductive physiology. The objectives of this study weretoget insight into the function of leptin during the periparturient period and to perform an association study between polymorphisms in the bovine leptin and leptin receptor gene and fertility and production traits.The leptin gene including its promoter region and parts of the leptin receptor gene were sequenced to find polymorphisms,and related to differences in fertility and production traits.Leptin levels were described during the periparturient period in dairy cows and also associations with the genotyped polymorphisms and fertility and production traits were calculated.In Chapter 2 a literature overview regarding leptin and its receptor and their role in metabolic processes and fertility was given. This Chapter also includes recent literature, which was published during the investigations that were described in other Chapters of this thesis.

    Physiology of Leptin

    In Chapter 4 leptin levels during the periparturient period in dairy cows were described and these levels were related to differences in production and reproduction traits. Leptin concentrations in the periparturient cow undergo remarkable changes; leptinconcentrations were high during late pregnancy and declined to a nadir at parturition.

    The reason of elevated plasma leptin during pregnancy in ruminants seems to be the increase in adipose tissue leptin mRNA due to the lack of a negative feedback (leptin resistance state) and the increase in adiposity. We observed an association of live weight during lactation and prepartum leptin concentrations (Chapter 4) but did not investigate the association between prepartum live weight and leptin concentrations.

    The reason of the decline in leptin levels towards parturition and during lactation is the mobilization of adipose tissue. Leptin concentrations seem to reflect the state of energy balance during lactation; plasma leptin concentrations were lower in cows with a mean negative energy balance during lactation (Chapter 4).

    Further analysis indicated that a combination of three polymorphisms located at the leptin promoter region explained 14.3% of the variance in prepartum leptin concentrations. The two extreme combinations with the highest and lowest prepartum leptin concentrations could be used to investigate the function of leptin concentrations in pregnant cows.

    Genetics of Leptin

    Leptin influences feed intake, energy balance and fertility and therefore the leptin gene and the leptin receptor gene are possible candidate genes to investigate effects on energy balance and fertility in lactating cows. The leptin gene including its promoter region and parts of the leptin receptor gene were sequenced to find polymorphisms, but also to detect putative transcription factor binding sites on the leptin promoter region. An association study was performed with the found polymorphisms. Associations of allgenotyped polymorphisms with fertility and production traits measured in dairy cows during the periparturient period (Chapters 3 and 7) and alsodifferences in leptin levels between genotypes of all genotyped polymorphisms were analyzed (Chapters 5, 6, and 7).

    An intronic polymorphism (RFLP1) located on intron 2 of the leptin gene explained a significant part of the variation in milk yield, with differences of 0.5 genetic standard deviation between the two extreme genotypes (Chapter 3). However, because this polymorphism is located at an intronic region and because the polymorphisms found in the exons of the leptin gene were not associated with milk yield, we can not exclude that the causative gene is in linkage disequilibrium with this polymorphism. On the promoter region of the leptin gene SNP -1457 was associated with first postpartum luteal activity ( p =0.017) and with weight loss between week 1 and its minimum weight ( p =0.027), where more weight loss occurred together with a later first postpartum luteal activity.Fertility traits are considered to be important to select for and this SNP could be a potential candidate marker to be informative for fertility in dairy cows. SNP -963 was associated with energy balance ( p =0.015) and dry matterintake (p = 0.030), where a higher dry matter intake occurred together with a higher energy balance (Chapter 7).

    In order to find an optimal genotype combination with a high milk yield, a good energy balance and fertility some new analysis were performed in Chapter 8. Two genotype combinations of three SNPs were defined in this Chapter and a next experiment and calculations of economical values per trait have to validate if one of these genotype combinations would be a possible candidate to be used in selection.

    The R4C polymorphism, located at exon 2 of the leptin gene, received a lot of attention by several research groups because of its putative effect on the leptin structure, but several studies, including our study, did not provide convincing evidence that the R4C polymorphism influences the structure and function of leptin. Other studies showed an effect on milk yield in dairy cattle and carcass fat content in beef cattle. On the basis of these results a commercially available R4C-test was developed to improve breeding values in both dairy and beef cattle.

    Polymorphisms in the leptin and leptin receptor gene have shown to be associated with differences in leptin concentration during late pregnancy (Chapters 5 and 6) but, surprisingly, not during lactation. As the promoter of leptin regulates the expression of leptin, polymorphisms at this region could play an important role in the found differences in plasma leptin levels during late pregnancy. Therefore in Chapter 7 we sequenced the leptin promoter and analyzed the sequence for transcription factor binding sites and polymorphisms. All genotyped polymorphisms were associated with prepartum leptin concentrations but in Chapter 8 we showed that three polymorphisms located on a 135 bp promoter region (282 to 147 bp before the transcription start site) seemed to be important for differences in leptin concentrations during late pregnancy. Also significant differences during the lactation period were found between the two genotype combinations with the highest en lowest leptin concentrations. We proposed a putative pregnancy-dependent enhancer to be located at this site on the leptin promoter.

    In conclusion, polymorphisms in the leptin gene and its promoter region are associated with traits in dairy cattle like milk yield (RFLP1), energy balance (SNP -963) and fertility (SNP -1457). Further experiments and calculations are needed to investigate if a combination of these three polymorphisms would be useful in future selection. On the promoter region a pregnancy-dependent enhancer might be located. A combination of polymorphisms located at this region might be useful to investigate the function of high leptin levels during pregnancy.

    Stillbirth in the pig in relation to genetic merit for farrowing survival
    Leenhouwers, J.I. ; Wissink, P. ; Lende, T. van der; Paridaans, H. ; Knol, E.F. - \ 2003
    Journal of Animal Science 81 (2003). - ISSN 0021-8812 - p. 2419 - 2424.
    preweaning mortality - swine - traits - parturition - parameters - selection - growth - birth
    The objectives of this study were to analyze the incidence of different categories of stillborn piglets in relation to genetic merit for farrowing survival of sows and litters and to analyze relationships of total number of piglets born per litter, average BW of the litter, and within-litter variation in BW with genetic merit for farrowing survival of sows and litters. Records of 336 purebred litters, produced by 307 first-to eighth-parity sows, were collected on a nucleus farm in Brouennes, France. Breeding values for farrowing survival were estimated for sows (EBVfs(-)maternal) and litters (EBVfs(-)direct) using a large data set from which information obtained in the current study was excluded. For each litter, BW, number of stillborn piglets (classified as nonfresh stillborn, prepartum stillborn, intrapartum stillborn, and postpartum stillborn), and number of live-born piglets were recorded. Birth weights of stillborn piglets were lower than BW of live-born piglets (P <0.0001), except for prepartum stillbirths. The total number of stillborn piglets per litter and the number of stillborn piglets in each category decreased with increasing EBVfs(-)maternal (P <0.01). An increase in EBVfs(-)direct was also associated with a decrease in the total number of stillborn piglets per litter (P <0.01). This decrease was due to a decrease in the number of nonfresh, prepartum, and postpartum stillborn piglets but not to a decrease in the number of intrapartum stillborn piglets. Probabilities of stillbirth in relation to EBVf(-)maternal were higher than probabilities of stillbirth in relation to EBVf direct. Total number of piglets born decreased with increasing EBVfs(-)direct (P = 0.0003), but was not related to EBVfs(-)maternal. Average BW of the litter (P <0.0001) and within-litter variation in BW (P = 0.05) decreased with increasing EBVfs(-)maternal but were not related to EBVfs(-)direct. Selection for the maternal genetic component of farrowing survival seems a better strategy than selection for the direct genetic component. Selection for the maternal genetic component of farrowing survival reduces stillbirth in all categories and does not affect litter size.
    The influence of induced parturition and the moment of vaccination against Swine erysipelas during lactation on the weaning-to-oestrus interval in sows
    Vonk, M.C. ; Binnendijk, G.P. ; Vesseur, P.C. - \ 1999
    Rosmalen : Research Institute for Pig Husbandry (Research report / Research Institute for Pig Husbandry P 5.9) - 24
    varkenshouderij - vaccinatie - varkensziekten - varkens - worpresultaten - prestatieniveau - partus - partusinterval - pig farming - vaccination - swine diseases - pigs - litter performance - performance - parturition - parturition interval
    This experiment was carried out to investigate the effect of vaccination during lactation with PorciW Ery+Parvo on the weaning-to-oestrus interval and the reproduction in sows. An exploratory study had indicated that vaccination during particularly the first few days of lactation might lead to a longer weaning-to-oestrus interval. To find out whether vaccination during lactation and/orthe moment of vaccination actually affects the weaning-to-oestrus interval, sows were vaccinated the first, second or last weeks of lactation with either Porcilis@ Ery+Parvo or a placebo. In the same experiment the combination with induced parturition on the weaning-to-oestrus interval was examined. Also the influence of the treatments on the use of PGGOO@ was considered, as was pregnancy rate from first insemination and litter size, and the number of stillborn piglets or born alive in the subsequent litter. The main results and conclusions are: 1- Vaccination of sows during the first week of lactation (with PorciW Ery+Parvo) against Swine erysipelas and Parvo has no significant adverse effect on reproductive performance. 2- Induced parturition causes earlier parturition, which results in lighter piglets. Induced parturition has no effect on percentage of piglets born alive; the percentage of piglets with splay leg is significantly higher
    De invloed van geboorte-inductie en het tijdstip van Vlekziekte-vaccinatie tijdens de zoogperiode op het interval spenen-bronst van zeugen
    Vonk, M.C. ; Binnendijk, G.P. ; Vesseur, P.C. - \ 1999
    Rosmalen : Praktijkonderzoek varkenshouderij (Proefverslag / Praktijkonderzoek Varkenshouderij P1.220) - 40
    zeugen - partus - vaccinatie - varkensziekten - postspeeninterval - timing - sows - parturition - vaccination - swine diseases - postweaning interval - timing
    Het doel van dit onderzoek was het bestuderen van het effect van vaccinatie gedurende de zoogperiode met het vlekziekte-parvovaccin Porcilis@ Ery+Parvo op het interval spenen-bronst en de reproductieresultaten van zeugen. Oriënterend onderzoek had aanwijzingen gegeven dat het tijdstip van vaccineren gedurende de zoogperiode van invloed lijkt op het interval spenen-bronst, met name dat vaccinatie in het begin van de zoogperiode dit interval zou kunnen verlengen. Om te kunnen achterhalen of vaccinatie gedurende de zoogperiode en/of het tijdstip van vaccinatie gedurende de zoogperiode inderdaad effect heeft op het interval spenen-bronst, zijn de zeugen in dit onderzoek in de eerste, tweede of laatste week van de zoogperiode behandeld met of het vaccin Porcilis@ Ery+Parvo of met een placebo. Ook is onderzocht of het al of niet combineren van deze behandeling met geboorte-inductie invloed had op het interval spenen-bronst
    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
    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
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