排序方式： 共有45条查询结果，搜索用时 31 毫秒
1.
2.
H. Täubert D. Agena & H. Simianer 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2007,124(3):117-123
The aim of this study was to analyse racing performance data in Irish greyhounds with regard to genetic and environmental variation. Estimation of heritabilities for racing time (RT) and ranking, and the prediction of breeding values for all greyhounds in the investigated data were carried out. Data from 42,785 races in Ireland in the years 2000-2003 were available. These results were obtained from 42,880 greyhounds on 20 race tracks over a distance of 480 m. Three traits were analysed, RT, ranking and a scaled logarithmic function for RT (ART), which was used to adjust racing time to be normally distributed. The data were analysed with a bivariate animal model. The estimated heritabilities were moderate for RT (0.31) and ART (0.38), but very low for ranking (0.10). The repeatabilities were 0.56 (RT), 0.51 (ART) and 0.13 (ranking). The genetic correlations were very high, 0.99 (RT-ranking) and 0.96 (ART-ranking), while the phenotypic correlation was lower, 0.60 (RT-ranking) and 0.62 (ART-ranking). The genetic trend for the traits as well as the phenotypic change of the average RT was positive. 相似文献
3.
The aim of this study was to estimate the current level of inbreeding in the German cow population and for bull dams born in Germany, to find out sires most related to different subsets of their breed and to demonstrate the negative effect of homozygosity in the case of complex vertebral malformation (CVM). Further on, the application of optimum genetic contribution (OGC) theory for the selection of bull dams and bull sires in different breeding scenarios was investigated. Levels of inbreeding for the cow population were in a low range from 0.97% to 1.70% evaluating birth years from 1996 to 1999 in a total dataset of 244,427 registered Holstein cows. The inbreeding coefficient of 8030 bull dams was much higher, i.e. 3.71%, for the birth year 1999. Increases in inbreeding of 0.19% per year indicated an effective population size of only 52 animals. Individual sires like R.O.R.A. Elevation and Hannoverhill Starbuck were highly related to potential bull dams with coefficients of relationship of 13.4% and 12.9%, respectively, whereas P.F. Arlinda Chief (16.3%) and Carlin-M Ivanhoe Bell (16.1%) were highest related to the best available AI sires. Coefficients of relationship were calculated by classes of estimated breeding values (EBV) for production traits showing highest values above 7% in the two highest EBV-classes. The optimum genetic contribution theory using official EBVs and approximative, for zero inbreeding corrected EBVs, was applied for elite matings in a breeding program embracing 30 young bulls per year to find the optimal allocations of bull sires and bull dams. Compared with the actual breeding program applied in practice, OGC-theory has the potential to increase genetic gain under the same constraint for the increase of average relationship by 13.1%. A more relaxed constraint on increase in inbreeding allowed even higher expected genetic gain whereas a more severe constraint resulted in more equal contributions of selected bull sires. Contributions from 21 selected bull sires and 30 selected bull dams for a scenario at 5% constrained relationship were used to develop a specific mating plan to minimise inbreeding in the short term in the following generation applying a simulated annealing algorithm. The expected coefficient of inbreeding of progeny was 66.3% less then the one resulting from random mating. Mating programs can address inbreeding concerns on the farm, at least in the short term, but long-term control of inbreeding in a dairy population requires consideration of relationships between young bulls entering AI progeny test programs. Significantly better EBVs of CVM-free bulls compared with CVM-carriers for the paternal fertility justify the application of OGC for elite matings. 相似文献
4.
The Goettingen minipig is a laboratory animal especially developed for medical research. For easy and comfortable handling during experiments, and to minimize costs, a low BW is essential. To breed for an even smaller minipig, genetic parameters for BW were estimated using a random regression model (RRM). The RRM was calculated using random animal, common litter environment, and permanent environment effects, respectively. Regressions for the random effects in the RRM were modeled using Legendre polynomials from second to fourth order of fit in different combinations. The model was applied to a data set that focused on the time period from 30 to 400 d of age. Eight age classes were built to consider heterogeneous residual variances. The heritabilities were moderate and ranged from 0.211 (375 d of age) to 0.254 (275 d of age). The variances initially decreased and then increased toward the end of the examined time period for permanent environment and litter effects. Genetic and phenotypic correlations between BW in different age classes decreased with increasing distance between age classes. The major eigenfunction showed positive values throughout the whole trajectory (i.e., a selection for low BW had positive effects on this trait throughout the whole range of time). On the basis of the estimated genetic parameters, a breeding scheme can be created to develop genetically smaller Goettingen minipigs in the future. 相似文献
5.
F Ytournel S Teyssèdre D Roldan M Erbe H Simianer D Boichard H Gilbert T Druet A Legarra 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2012,129(5):417-421
Simulations are a major tool to evaluate new statistical methods and optimize experimental designs in the genomic era. However, this can only be achieved when the simulations are close enough to reality, as well as diverse enough to be realistic. For mapping studies, it is thus critical to re-create as much as possible the forces generating linkage (mutation, random drift, changes in population sizes, selection and pedigree structure) and the mechanisms producing trait genetic architecture (additivity, dominance, epistasis). We present here a computer program (ldso) simulating these phenomena. Optional outputs provide statistics on the linkage disequilibrium (LD) structure and the identity by descent between chromosomal segments, facilitating further data analyses. Furthermore, ldso enables the simulation of genomic data in known pedigrees, which sticks as precisely as possible to recent population history and structures of the long-range LD, allowing optimization of fine-mapping strategies. 相似文献
6.
7.
遗传距离与利用微卫星进行系统树构建初探 总被引：2，自引：0，他引：2
以中国牛亚科家畜6个群体12对微卫星数据为基础,采用6种遗传距离（DA、DC、DS、DSW,（σμ）^2和DTL）和2种聚类方法（UPGMA和NJ法）,探索它们对系统树构建准确性的影响。结果表明：微卫星位点平均杂合度水平显著影响系统树构建的准确性,用DA和DC遗传距离构建的系统树准确性相对较高,但很难确定NJ法和UPGMA法哪一种更适合于系统树的构建,而DTL遗传距离用于系统树构建有待进一步完善;最后,对微卫星用于家畜系统树构建的有效性和局限性进行了探讨。 相似文献
8.
9.
M. Pashmi S. Qanbari S.A. Ghorashi A.R. Sharifi & H. Simianer 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2009,126(4):296-303
The major histocompatibility complex (MHC) is a gene complex closely linked to the vertebrate immune system due to its importance in antigen recognition and immune response to pathogens. To improve our understanding of the MHC and disease resistance in dairy cattle, we gathered 5119 test day records of somatic cell count (SCC) and performance traits of 262 Holstein dairy cows to determine whether the DRB region of the MHC contains alleles that are associated with elevated SCC, milk yield, protein and fat percent of milk. To this purpose, genotyping of animals for DRB3 gene was investigated by polymerase chain reaction‐based restriction fragment length polymorphism (PCR‐RFLP) assay. A two‐step PCR was carried out so as to amplify a 284 base‐pair fragment of exon 2 of the target gene. Second PCR products were treated with three restriction endonuclease enzymes RsaI, BstYI and HaeIII. Twenty‐eight BoLA‐DRB3 alleles were identified including one novel allele (*40). The results in general are in good accordance with allele frequencies of Holstein cattle populations reported by previous studies. Analyses of associations were modeled based on repeated measurement anova and generalized logistic linear methods for production traits and SCC data, respectively. The results of this study showed a significant relationship between the elevated SCC reflecting an increased probability of occurrence to subclinical mastitis and DRB3.2 allele *8 (p < 0.03). The results also revealed significant positive relationships of alleles*22 (p < 0.01) and allele*11 (p < 0.05) with milk fat percent as well as of alleles*24 (p < 0.03) and *22 (p < 0.05) with protein percent. The present study failed to find any association between milk yield and tested alleles. Because of the lack of consistency among results of similar studies, we suggest further investigations to determine the precise nature of these associations with the high polymorphic bovine MHC region to be performed based on haplotypes. 相似文献
10.
Erbe M Ytournel F Pimentel EC Sharifi AR Simianer H 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2011,128(1):3-14
Selection is known to influence the linkage disequilibrium (LD) pattern in livestock populations. Spurious LD may lead to a higher number of false-positive signals in whole genome association mapping experiments. We compared three approaches for whole genome association mapping in a simulation study: single marker regression (SMR), a two-step approach, which analyses residuals corrected for family effects with an SMR (GRAMMAR), and a combined linkage and LD approach, which applies the quantitative transmission disequilibrium test to the Mendelian sampling term (MTDT). Three different scenarios were simulated: idealized random mating, limited number of parents and directional selection. The number of false-positive associations increased when the number of parents was limited. Mapping accuracy was the worst in the scenario with directional selection for all approaches. As SMR produced a high number of false-positive signals in small populations, results of whole genome scans in livestock analysed with SMR should be considered with caution. GRAMMAR was the most accurate approach, but also the least powerful one. The Bonferroni-corrected significance threshold seemed to be too stringent for this approach. Results obtained with MTDT changed only slightly with selected populations. MTDT combined sufficient power with a manageable number of false-positive associations in all scenarios. 相似文献