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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Genetic parameters for atypical reproductive patterns in dairy cows estimated from in-line milk progesterone profiles
Binsbergen, R. van; Bouwman, A.C. ; Veerkamp, R.F. - \ 2019
Journal of Dairy Science 102 (2019)12. - ISSN 0022-0302 - p. 11104 - 11115.
endocrine - fertility - genetic correlation - heritability

Our aim was to estimate genetic parameters of atypical reproductive patterns and estimate their genetic correlation with milk production and classical fertility traits for commercial dairy cows. In contrast with classical fertility traits, atypical reproductive patterns based on in-line milk progesterone profiles might have higher heritability and lower genetic correlation with milk production. We had in-line milk progesterone profiles available for 12,046 cycles in 4,170 lactations of 2,589 primiparous and multiparous cows (mainly Holstein Friesian) from 14 herds. Based on progesterone profiles, 5 types of atypical reproductive patterns in a lactation were defined: delayed ovulation types I and II, persistent corpus luteum types I and II, and late embryo mortality. These atypical patterns were detected in 14% (persistent corpus luteum type II) to 21% (persistent corpus luteum type I) of lactations. In 47% of lactations, at least 1 atypical pattern was detected. Threshold model heritabilities for atypical reproduction patterns ranged between 0.03 and 0.14 and for most traits were slightly higher compared with classical fertility traits. The genetic correlation between milk yield and calving interval was 0.56, whereas genetic correlations between milk yield and atypical reproductive patterns ranged between −0.02 and 0.33. Although most of these correlations between milk yield and atypical reproductive patterns are still unfavorable, they are lower compared with the correlations between classical fertility traits and milk yield. Therefore selection against atypical reproductive patterns may relax some constraints in current dairy breeding programs, to enhance genetic progress in both fertility and milk yield at a steady pace. However, as long as the target trait for fertility is calving interval, atypical reproductive patterns will not add additional value to the breeding goal in the near future due to the low number of available records.

Genetic parameters for αS1-casein and αS2-casein phosphorylation isoforms in Dutch Holstein Friesian
Fang, Z.H. ; Bovenhuis, H. ; Valenberg, H.J.F. van; Martin, P. ; Huppertz, T. ; Visker, M.H.P.W. - \ 2018
Journal of Dairy Science 101 (2018)2. - ISSN 0022-0302 - p. 1281 - 1291.
capillary zone electrophoresis - genetic correlation - milk protein composition - posttranslational modification
Relative concentrations of αS1-casein and αS2-casein (αS1-CN and αS2-CN) phosphorylation isoforms vary considerably among milk of individual cows. We estimated heritabilities for αS2-CN phosphorylation isoforms, determined by capillary zone electrophoresis from 1,857 morning milk samples, and genetic correlations among αS2-CN phosphorylation isoforms in Dutch Holstein Friesian. To investigate if phosphorylation of αS1-CN and αS2-CN are due to the same genetic mechanism, we also estimated genetic correlations between αS1-CN and αS2-CN phosphorylation isoforms as well as the genetic correlations between the phosphorylation degrees (PD) of αS1-CN and αS2-CN defined as the proportion of isoforms with higher degrees of phosphorylation in total αS1-CN and αS2-CN, respectively. The intra-herd heritabilities for the relative concentrations of αS2-CN phosphorylation isoforms were high and ranged from 0.54 for αS2-CN-10P to 0.89 for αS2-CN-12P. Furthermore, the high intra-herd heritabilities of αS1-CN PD and αS2-CN PD imply a strong genetic control of the phosphorylation process, which is independent of casein production. The genetic correlations between αS2-CN phosphorylation isoforms are positive and moderate to high (0.33–0.90). Furthermore, the strong positive genetic correlation (0.94) between αS1-CN PD and αS2-CN PD suggests that the phosphorylation processes of αS1-CN and αS2-CN are related. This study shows the possibility of breeding for specific αS1-CN and αS2-CN phosphorylation isoforms, and relations between the phosphorylation degrees of αS1-CN and αS2-CN and technological properties of milk need to be further investigated to identify potential benefits for the dairy industry.
Modeling genetic and nongenetic variation of feed efficiency and its partial relationships between component traits as a function of management and environmental factors
Lu, Y. ; Vandehaar, M.J. ; Spurlock, D.M. ; Weigel, K.A. ; Armentano, L.E. ; Staples, C.R. ; Connor, E.E. ; Wang, Z. ; Coffey, M. ; Veerkamp, R.F. ; Haas, Y. de; Tempelman, R.J. - \ 2017
Journal of Dairy Science 100 (2017)1. - ISSN 0022-0302 - p. 412 - 427.
dry matter intake - genetic correlation - heritability - hierarchical Bayesian modeling
Feed efficiency (FE), characterized as the fraction of feed nutrients converted into salable milk or meat, is of increasing economic importance in the dairy industry. We conjecture that FE is a complex trait whose variation and relationships or partial efficiencies (PE) involving the conversion of dry matter intake to milk energy and metabolic body weight may be highly heterogeneous across environments or management scenarios. In this study, a hierarchical Bayesian multivariate mixed model was proposed to jointly infer upon such heterogeneity at both genetic and nongenetic levels on PE and variance components (VC). The heterogeneity was modeled by embedding mixed effects specifications on PE and VC in addition to those directly specified on the component traits. We validated the model by simulation and applied it to a joint analysis of a dairy FE consortium data set with 5,088 Holstein cows from 13 research stations in Canada, the Netherlands, the United Kingdom, and the United States. Although no differences were detected among research stations for PE at the genetic level, some evidence was found of heterogeneity in residual PE. Furthermore, substantial heterogeneity in VC across stations, parities, and ration was observed with heritability estimates of FE ranging from 0.16 to 0.46 across stations.
Genetic changes of survival traits over the past 25 yr in Dutch dairy cattle
Pelt, M.L. van; Ducrocq, V. ; Jong, G. de; Calus, M.P.L. ; Veerkamp, R.F. - \ 2016
Journal of Dairy Science 99 (2016)12. - ISSN 0022-0302 - p. 9810 - 9819.
genetic correlation - longevity - survival

Genetic correlations and heritabilities for survival were investigated over a period of 25 yr to evaluate if survival in first lactation has become a different trait and if this is affected by adjusting for production level. Survival after first calving until 12 mo after calving (surv_12mo) and survival of first lactation (surv_1st_lac) were analyzed in Dutch black-and-white cows. The data set contained 1,108,745 animals for surv_12mo and 1,062,276 animals for surv_1st_lac, with first calving between 1989 and 2013. The trait survival as recorded over 25 yr was split in five 5-yr intervals to enable a multitrait analysis. Bivariate models using subsets of the full data set and multitrait and autoregressive models using the full data set were used. Survival and functional survival were analyzed. Functional survival was defined as survival adjusted for within-herd production level for 305-d yield of combined kilograms of fat and protein. Mean survival increased over time, whereas genetic variances and heritability decreased. Bivariate models yielded large standard errors on genetic correlations due to poor connectedness between the extreme 5-yr intervals. The more parsimonious models using the full data set gave nonunity genetic correlations. Genetic correlations for survival were below 0.90 between intervals separated by 1 or more 5-yr intervals. Genetic correlations for functional survival did not indicate that definition of survival changed (≥0.90). The difference in genetic correlations between survival and functional survival is likely explained by lower emphasis of dairy farmers on culling in first lactation for low yield in more recent years. This suggests that genetic evaluation for longevity using historical data should analyze functional survival rather than survival.

Heritabilities and genetic correlations for honey yield, gentleness, calmness and swarming behaviour in Austrian honey bees
Brascamp, Evert ; Willam, Alfons ; Boigenzahn, Christian ; Bijma, Piter ; Veerkamp, Roel F. - \ 2016
Apidologie 47 (2016)6. - ISSN 0044-8435 - p. 739 - 748.
estimated breeding value - genetic correlation - genetic parameter - heritability - honey bee

Heritabilities and genetic correlations were estimated for honey yield and behavioural traits in Austrian honey bees using data on nearly 15,000 colonies of the bee breeders association Biene Österreich collected between 1995 and 2014. The statistical models used distinguished between the genetic effect of workers and that of the queen of the colony. Heritability estimates for worker effect were larger than those for queen effect. Genetic correlations between both effects were negative. Heritability estimates for the sum of both effects (i.e. selection criterion) were 0.27, 0.37, 0.38 and 0.06 for honey yield, gentleness, calmness and swarming behaviour, respectively, indicating that meaningful genetic improvement is possible. Genetic correlations between these traits were generally small to medium, with large standard errors, with the exception of the high genetic correlation between gentleness and calmness. The models we present here can be used to estimate breeding values in honey bees.

Breeding against infectious diseases in animals
Rashidi, H. - \ 2016
Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Herman Mulder; P.K. Mathur. - Wageningen University - ISBN 9789462576452 - 179
livestock - infectious diseases - animal breeding - selective breeding - disease resistance - tolerance - genetic variation - breeding value - genetic correlation - traits - genomics - animal genetics - vee - infectieziekten - dierveredeling - selectief fokken - ziekteresistentie - tolerantie - genetische variatie - fokwaarde - genetische correlatie - kenmerken - genomica - diergenetica

Infectious diseases in farm animals are of major concern because of animal welfare, production costs, and public health. Farms undergo huge economic losses due to infectious disease. The costs of infections in farm animals are mainly due to production losses, treatment of infected animals, and disease control strategies. Control strategies, however, are not always successful. Selective breeding for the animals that can mount a defence against infection could therefore be a promising approach. Defensive ability of an animal has two main mechanisms: resistance (ability to control the pathogen burden) and tolerance (ability to maintain performance when pathogen burden increases). When it is difficult to distinguish between resistance and tolerance, defensive ability is measured as resilience that is the ability to maintain performance during a disease outbreak regardless of pathogen burden. Studies have focused on the genetics of resistance and resilience with little known about the genetics of tolerance and its relationship with resistance and resilience. The objectives of this thesis were to: 1) estimate the genetic variation in resistance, tolerance, and resilience to infection in order to assess the amenability of these traits for selective breeding in farm animals, 2) estimate the genetic correlation between resistance, tolerance and resilience and 3) detect genomic regions associated with resistance, tolerance, and resilience.

In chapter 2, we studied the variation among sows in response to porcine reproductive and respiratory syndrome (PRRS). First a statistical method was developed to detect PRRS outbreaks based on reproduction records of sows. The method showed a high sensitivity (78%) for disease phases. Then the variation of sows in response to PRRS was quantified using 2 models on the traits number of piglets born alive (NBA) and number of piglets born dead (LOSS): 1) bivariate model considering the trait in healthy and disease phases as different traits, and 2) reaction norm model modelling the response of sows as a linear regression of the trait on herd-year-week estimates of NBA. Trait correlations between healthy and disease phases deviated from unity (0.57±0.13 – 0.87±0.18). The repeatabilities ranged from 0.07±0.027 to 0.16±0.005. The reaction norm model had higher predictive ability in disease phase compared to the bivariate model.

In chapter 3 we studied 1) the genetic variation in resistance and tolerance of sheep to gastrointestinal nematode infection and 2) the genetic correlation between resistance and tolerance. Sire models on faecal nematode egg count (FEC), IgA, and pepsinogen were used to study the genetic variation in resistance. Heritability for resistance traits ranged from 0.19±0.10 to 0.59±0.20. A random regression model was used to study the reaction norm of sheep body weight on FEC as an estimate of tolerance to nematode infection. We observed a significant genetic variance in tolerance (P<0.05). Finally a bivariate model was used to study the genetic correlation between resistance and tolerance. We observed a negative genetic correlation (-0.63±0.25) between resistance and tolerance.

In chapter 4, we studied the response to selection in resistance and tolerance when using estimated breeding values for resilience. We used Monte Carlo simulation to generate 100 half-sib families with known breeding values for resistance (pathogen burden) and tolerance. We used selection index theory to predict response to selection for resistance and tolerance: 1) when pathogen burden is known and selection is based on true breeding values for resistance and tolerance and 2) when pathogen burden is unknown and selection is based on estimated breeding values for resilience. Using EBV for resilience in absence of records for pathogen burden resulted in favourable responses in resistance and tolerance to infections, with more emphasis on tolerance than on resistance. However, more genetic gain in resistance and tolerance could be achieved when pathogen burden was known.

In chapter 5 we studied genomics regions associated with resistance, resilience, and tolerance to PRRS. Resistance was modelled as sire effect on area under the PRRS viremia curve up to 14 days post infection (AUC14). Resilience was modelled as sire effects on daily growth of pigs up to 28 days post infection (ADG28). Tolerance was modelled as the sire effect on the regression of ADG28 on AUC14. We identified a major genomics region on chromosome 4 associated with resistance and resilience to PRRS. We also identified genomics regions on chromosome 1 associated with tolerance to PRRS.

In the general discussion (chapter 6) I discussed: 1) response to infection as a special case of genotype by environment interaction, 2) random regression model as a statistical tool for studying response to disease, 3) advantages and requirements of random regression models, and 4) selective breeding of farm animals for resistance, tolerance, and resilience to infections. I concluded that random regression is a powerful approach to estimate response to infection in animals. If the adequate amount of data is available random regression model could estimate breeding values of animals more accurately compared to other models. I also concluded that before including resistance and tolerance into breeding programs, breeders should make sure about the added values of including these traits on genetic progress. Selective breeding for resilience could be a pragmatic approach to simultaneously improve resistance and tolerance.

Sport horses : breeding specialist from a single breeding programme?
Rovere, G.A. - \ 2016
Wageningen University; Aarhus University. Promotor(en): Johan van Arendonk, co-promotor(en): P. Madsen; Bart Ducro; E. Norberg. - Wageningen : Wageningen University - ISBN 9789462576353 - 151
horses - racehorses - studbooks - show jumping - sport performance - pedigree - genetic correlation - horse breeding - breeding programmes - paarden - renpaarden - paardenstamboeken - jachtspringen - sportprestatie - stamboom - genetische correlatie - paardenfokkerij - veredelingsprogramma's


The general goal of this thesis was to provide information useful for the breeding programme of the Royal Dutch Warmblood Studbook (KWPN) in relation with the ongoing specialisation of the population. Data provided by KWPN consisted of records from studbook-first inspection, competition performance on dressage and show-jumping, and pedigree information. Firstly, the effect of specialisation was studied on the connectedness between the subpopulations of dressage and show-jumping horses, using the pedigree information. Results indicated that relatedness between horses in the two subpopulations has been reduced to a low level, while relatedness within both subpopulations has been increasing consistently. A reduction in the number of influential ancestors in both subpopulations was observed. Secondly, it was analysed whether the specialisation for either dressage or show jumping has affected genetic parameters of traits recorded in the two subpopulations. Traits recorded at studbook-entry inspection were defined as a dressage trait or a show-jumping trait according to the type of horse that received the inspection. Bivariate analyses were performed to estimate the genetic correlation between the two traits. Results indicated that the specialisation process has resulted in a difference in mean trait values between dressage and show-jumping horses. However, differences in heritabilities for traits defined as dressage or show-jumping did not differ significantly, and the genetic correlations between them were not different from one considering their posterior standard deviation. Thirdly, the model to analyse performance in competition of dressage and show-jumping was studied. Results showed that performance in competition for dressage and show-jumping is a heritable trait (h2 ~ 0.11-0.13), and that it is important to account for the effect of rider in the genetic analysis. Fourthly, it was estimated the genetic correlation between the performance of horses in dressage and show-jumping competition, and the genetic correlations between traits measured early in life and performance in competition in each of the disciplines. Results showed that the genetic correlation between performance of horses in dressage and show-jumping was slightly unfavourable (-0.12). The genetic correlation between dressage and show-jumping tended to become more unfavourable over time, but this trend was not reflected in changes in the correlations between competition traits and traits recorded in the studbook-entry inspection. From this study it can be concluded that no extra benefit is to be expected from definition of a combined breeding goal. However, entirely separated breeding programmes for both disciplines are therefore not advisable. Constructing separate selection indexes would allow for optimal weighting of information sources such as studbook-entry inspection traits in accordance to the breeding goal of each sports discipline.

Genetic and phenotypic parameter estimates for growth traits of Hainan Black goat in southern China
Zhou, Han Lin ; Gu, Li Hong ; Sun, Yanyan ; Xu, Tie Shan ; Rong, Guang - \ 2015
Animal Production Science 55 (2015)4. - ISSN 1836-0939 - p. 447 - 453.
bodyweight - genetic correlation - growth rate - heritability

Genetic improvement of the growth of Hainan Black goats is a major concern as the breed is an important meat-type goat raised in southern China. To estimate genetic and phenotypic parameters for growth traits for this breed, a population of 1354 Hainan Black goats born and maintained at the Hainan Black Goat Breeding Farm from 2007 to 2011 was used. Heritabilities and phenotypic and genetic correlations for bodyweights (BWs) at birth and at 2, 4, 6, 8, 10 and 12 months of age (denoted as BW0, BW2, BW4, BW6, BW8, BW10 and BW12, respectively) and average daily weight gains (ADGs) from birth to 2 months, from 2 to 6 months, and from 6 to 12 months (denoted as ADG0-2, ADG2-6 and ADG6-12, respectively) were estimated using an animal model, with and without a permanent maternal environmental effect fitted as a random effect. Litter size, kidding year, birth season and sex, as well as their interactions, were investigated as fixed effects. Likelihood ratio testing indicated that the model with a permanent maternal environmental effect was better than that without a permanent maternal environmental effect for all traits. The direct additive heritability for BW and ADG ranged from 0.17 (ADG6-12) to 0.45 (BW0), indicating that growth traits of Hainan Black goats can be improved by phenotypic selection. Maternal permanent environmental variance was also estimated and varied from 0.08 (BW6) to 0.27 (BW10). The genetic and phenotypic correlations among ADG traits were positive and relatively low. However, the positive and relatively high genetic and phenotypic correlations among BW traits indicated that breeding programs are able to use selection at early ages to improve BW traits.

The potential of genomic selection to support local breed conservation
Calus, Mario - \ 2014
animal breeding - genotypes - phenotypes - genetic variance - genomics - genetic correlation - irish republic - beef cows - animal genetic resources - breeds
Sociable swine: prospects of indirect genetic effects for the improvement of productivity, welfare and quality
Duijvesteijn, N. - \ 2014
Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Piter Bijma; E.F. Knol. - Wageningen : Wageningen University - ISBN 9789462571525 - 202
varkens - sociaal gedrag - groepsinteractie - genetische effecten - prestatieniveau - dierenwelzijn - androsteron - genomen - genetische correlatie - varkensfokkerij - stakeholders - beoordeling - dierlijke productie - pigs - social behaviour - group interaction - genetic effects - performance - animal welfare - androsterone - genomes - genetic correlation - pig breeding - stakeholders - assessment - animal production

Towards Healthy Diets for parents: efectiveness of a counselling intervention

Eveline J.C. Hooft van Huysduynen


Introduction and Objective: As parents’ modelling of dietary behaviour is one of the factors influencing children’s diets, improving parents’ diets is expected to result in improved dietary intake of their children. This thesis describes research that was conducted to develop and evaluate a counselling intervention to improve parental adherence to the Dutch dietary guidelines.

Methods: A counselling intervention was developed, which was underpinned with the theory of planned behaviour and the transtheoretical model. In 20 weeks, five face-to-face counselling sessions were provided by a registered dietician who used motivational interviewing to improve parental adherence to the Dutch dietary guidelines. In addition, parents received three individually tailored email messages. During the counselling, the dietary guidelines and additional eating behaviours, that were hypothesized to affect diet quality, were addressed. The intervention was evaluated in a randomised controlled trial with 92 parents receiving the counselling and 94 parents as controls. Effects on dietary intake, biomarkers, intermediate markers of health and children’s dietary intake were evaluated. With mediation analyses, it was investigated if changes in dietary intake were established via changes in behavioural determinants. Thereby, it was also examined if spot urine samples could be used to replace 24 h urine samples for evaluating changes in sodium and potassium intake.

Results: The intervention group increased their adherence to the dietary guidelines, as assessed with the Dutch Healthy Diet-index (ranging from 0 to 100 points), by 6.7 points more than the control group did. This improvement was achieved by small increases in the scores of seven out of ten index components. The most substantial changes were shown in fruit and fish intakes of which increases in fish intake were reflected in changes in fatty acid profiles derived from blood plasma. Also a small decrease in waist circumference was observed. Based on parental reports, the children in the intervention group increased their intakes of fruit, vegetables and fish more than the children in the control group. Improvements in parental fruit intake were mediated by changes in the behavioural determinants attitude and habit strength. Decreases in snack intake were mediated by changes in self-identity as a healthy eater. Although the results of a study in young Caucasian women showed that spot urine can be used to rank individuals for their ratios of sodium to potassium, no intervention effects on these ratios were observed.

Conclusion: This thesis provides empirical knowledge on potential effective elements for counselling interventions aiming at improving the dietary pattern as a whole of parents and provides knowledge on methods to evaluate changes in dietary intake.

Quantitative genetic analysis of ascites in broilers
Closter, A.M. - \ 2014
Wageningen University. Promotor(en): Martien Groenen; Johan van Arendonk; Henk Bovenhuis. - Wageningen : Wageningen University - ISBN 9789461738400 - 130
vleeskuikens - kwantitatieve genetica - ascites - genetische parameters - heritability - genetische correlatie - fenotypische correlatie - dierveredeling - genetica - kippenziekten - broilers - quantitative genetics - ascites - genetic parameters - heritability - genetic correlation - phenotypic correlation - animal breeding - genetics - fowl diseases

Ascites, also called pulmonary hypertension syndrome, is a metabolic disorder in chickens. The tendency to develop ascites is heritable, and successful selection will benefit from understanding the genetic background of ascites. The aims of this thesis were to (i) estimate genetic parameters for ascites indicator traits using standard and novel statistical methods and (ii) to perform a genome wide association study in order to identify chromosomal regions associated with ascites. It was shown that blood gas parameters, which have been previously suggested as indicator traits for ascites susceptibility, are of limited value in the selection against ascites susceptibility. Further, it was shown that the incidence of ascites is higher in male than in female broilers and this difference affects the genetic parameters.A liability normal mixture (LNM) model can account for differences in incidence of ascites. Analyses using the LNM model showed that almost a quarter of the chickens in the analyzed population are affected by ascites. Further, this analysis showed that the ratio of right to total ventricular weight (RATIO) is genetically not the same trait in healthy and diseased chickens. Finally, the results of a genome wide association study (GWAS) showed a number of chromosomal regions associated with ascites. No regions were detected with major effects on ascites. Therefore it seems that ascites is affected by a number of genes, each with a relatively small effect.

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.

Mapping phenotypic plasticity and genotype-environment interactions affecting life-history traits in Caenorhabditis elegans
Gutteling, E.W. ; Riksen, J.A.G. ; Bakker, J. ; Kammenga, J.E. - \ 2007
Heredity 98 (2007)1. - ISSN 0018-067X - p. 28 - 37.
arabidopsis-thaliana - drosophila-melanogaster - natural environments - genetic correlation - loci - pleiotropy - selection - fitness - span - polyphenism
Phenotypic plasticity and genotype-environment interactions (GEI) play an important role in the evolution of life histories. Knowledge of the molecular genetic basis of plasticity and GEI provides insight into the underlying mechanisms of life-history changes in different environments. We used a genomewide single-nucleotide polymorphism map in a recombinant N2 × CB4856 inbred panel of the nematode Caenorhabditis elegans to study the genetic control of phenotypic plasticity to temperature in four fitness-related traits, that is, age at maturity, fertility, egg size and growth rate. We mapped quantitative trait loci (QTL) for the respective traits at 12 and 24°C, as well as their plasticities. We found genetic variation and GEI for age at maturity, fertility, egg size and growth rate. GEI in fertility and egg size was attributed to changes in rank order of reaction norms. In case of age at maturity and growth rate, GEI was caused mainly by differences in the among-line variance. In total, 11 QTLs were detected, five QTL at 12°C and six QTL at 24°C, which were associated with life-history traits. Five QTL associated with age at maturity, fertility and growth rate showed QTL × environment interaction. These colocalized with plasticity QTL for the respective traits suggesting allelic sensitivity to temperature. Further fine mapping, complementation analyses and gene silencing are planned to identify candidate genes underlying phenotypic plasticity for age at maturity, fertility and growth
Selection for beef traits and calving performance in Piemontese cattle
Albera, A. - \ 2006
Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Ab Groen; P. Carnier. - [S.l. ] : S.n. - ISBN 9789085044796 - 175
vleesvee - vleesveerassen - selectief fokken - genetische verbetering - prestatiekenmerken - kalven - worpresultaten - vleesopbrengst - genetische correlatie - beef cattle - beef breeds - selective breeding - genetic improvement - performance traits - calving - litter performance - meat yield - genetic correlation
Fokken op lager ureum gehalte : zowel tussen als binnen rassen bestaan duidelijke verschillen in ureumgehalte
Veerkamp, R.F. ; Vuuren, A.M. van; Haan, M.H.A. de - \ 2005
Veeteelt 22 (2005)22. - ISSN 0168-7565 - p. 10 - 12.
melkveehouderij - melkkoeien - dierveredeling - dierlijke meststoffen - samenstelling - ureum - ammoniak - emissie - rasverschillen - heritability - genetische correlatie - dairy farming - dairy cows - animal breeding - animal manures - composition - urea - ammonia - emission - breed differences - genetic correlation
Het ureumgehalte wordt in de nieuwe mestwetgeving belangrijk, zodat een lager gehalte aantrekkelijk is voor veehouders die mest moeten afvoeren. In een onderzoek is daarom gekeken naar de mogelijkheid om het ureumgehalte via de fokkerij te verlagen. Gekeken is hierbij naar verschillen tussen rassen, genetische verschillen binnen een ras, de erfelijkheidsgraad en de genetische correlatie
Genetic analysis of ascites-related traits in broilers
Pakdel, A. - \ 2004
Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Henk Bovenhuis. - [S.l.] : S.n. - ISBN 9789085040477 - 133
vleeskuikens - pluimvee - ascites - kenmerken - genetische analyse - genetische parameters - heritability - maternale effecten - genetische correlatie - kwantitatieve kenmerken - genetische kartering - selectief fokken - broilers - poultry - ascites - traits - genetic analysis - genetic parameters - heritability - maternal effects - genetic correlation - quantitative traits - genetic mapping - selective breeding
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