Journal of Animal Breeding and Genetics
Công bố khoa học tiêu biểu
Sắp xếp:
Statistical aspects of design and analysis of experiments with animals in pens<sup>1</sup>
Journal of Animal Breeding and Genetics - Tập 106 Số 1-6 - Trang 321-334 - 1989
Analysis of pedigree and conformation data to explain genetic variability of the horse breed Franches‐Montagnes Summary Franches‐Montagnes is the only native horse breed in Switzerland, therefore special efforts should be made for ensuring its survival. The objectives of this study were to characterize the structure of this population as well as genetic variability with pedigree data, conformation traits and molecular markers. Studies were focused to clarify if this population is composed of a heavy‐ and a light‐type subpopulation. Extended pedigree records of 3‐year‐old stallions (n = 68) and mares (n = 108) were available. Evaluations of body conformation traits as well as pedigree data and molecular markers did not support the two‐subpopulation hypothesis. The generation interval ranged from 7.8 to 9.3 years. The complete generation equivalent was high (>12). The number of effective ancestors varied between 18.9 and 20.1, whereof 50% of the genetic variability was attributed to seven of them. Genetic contribution of Warmblood horses ranged from 36% to 42% and that of Coldblood horses from 4% to 6%. The average inbreeding coefficient reached 6%. Inbreeding effective population size was 114.5 when the average increase of the inbreeding coefficient per year since 1910 was taken. Our results suggest that bottleneck situations occurred because of selection of a small number of sire lines. Promotion of planned matings between parents that are less related is recommended in order to avoid a reduction of the genetic diversity.
Journal of Animal Breeding and Genetics - Tập 123 Số 2 - Trang 114-121 - 2006
Reliable computing in estimation of variance components Summary The purpose of this study is to present guidelines in selection of statistical and computing algorithms for variance components estimation when computing involves software packages. For this purpose two major methods are to be considered: residual maximal likelihood (REML) and Bayesian via Gibbs sampling. Expectation‐Maximization (EM) REML is regarded as a very stable algorithm that is able to converge when covariance matrices are close to singular, however it is slow. However, convergence problems can occur with random regression models, especially if the starting values are much lower than those at convergence. Average Information (AI) REML is much faster for common problems but it relies on heuristics for convergence, and it may be very slow or even diverge for complex models. REML algorithms for general models become unstable with larger number of traits. REML by canonical transformation is stable in such cases but can support only a limited class of models. In general, REML algorithms are difficult to program. Bayesian methods via Gibbs sampling are much easier to program than REML, especially for complex models, and they can support much larger datasets; however, the termination criterion can be hard to determine, and the quality of estimates depends on a number of details. Computing speed varies with computing optimizations, with which some large data sets and complex models can be supported in a reasonable time; however, optimizations increase complexity of programming and restrict the types of models applicable. Several examples from past research are discussed to illustrate the fact that different problems required different methods.
Journal of Animal Breeding and Genetics - Tập 125 Số 6 - Trang 363-370 - 2008
Mitochondrial respiratory metabolism and growth performance of lambs. II. Oxygen consumption and oxidative phosphorylation Summary Variation in mitochondrial respiratory metabolism, and associations of mitochondrial characteristics with growth traits, were studied in Merinolandschaf (n = 31) and Rhoenschaf (n = 27) lambs, as well as their reciprocal crosses — Rhoenschaf males × Merinolandschaf females (n = 25) and Merinolandschaf males × Rhoenschaf females (n = 31). Significant genotype effects were detected for all the growth parameters studied. Genotype was also significant for succinate‐mediated state 3 respiration of liver mitochondria (p < 0.01), and approached significance for ATP production with succinate as substrate and glutamate/malate‐mediated state 3 respiration. Significant trial effects (p < 0.001) were observed for all but one of the biochemical parameters studied. Variable patterns of significant correlations between biochemical characteristics and growth traits were detected, which were linked to performance levels of purebred and crossbred lambs. These results indicate that mitochondrial genes could influence growth in lambs via mitochondrial respiratory metabolism. Zusammenfassung Respiratorischer Metabolismus von Mitochondrien and Wachstum von Lämmern. II. Sauerstoff‐verbrauch und oxidative Phosphorylierung An Merinoland (n = 31) und Rhöhnschaflämmern (n = 27) sowie deren reziproken Kreuzungen Rhönscaf ♂ × Merinolandschaf ♀ (n = 25) und Merinolandschaf ♂ × Rhönschaf ♀ (n = 31) wurde die Variation im mitochondrialen Energiestoffwechsel untersucht und Beziehungen zwischen mitochondrialen Parametern und dem Lebendmassezuwachs ermittelt. Signifikante Genotypeffekte wurden bei alien erfaßten Wachstumsmerkmalen beobachtet. Der Effekt Genotyp war ebenfalls bei der succinatinduzierten Atraung von Lebermitochondrien signifikant (p < 0.01) und bewegte sich für die Merkmale ATP‐Produktion und Glutamat/Malat‐induzierte Atmung nahe der Signifikanzgrenze. Mit einer Ausnahme wurden für alle biochemischen Parameter hochsignifikante (p < 0.001) Untersuchungstagseffekte ermittelt. Die Muster signifikanter Korrelationen zwischen biochemischen Werten und Wachstumsmerkmalen waren uneinheitlich und vom Leistungsniveau der genetischen Gruppen abhängig. Die Ergebnisse zeigen, daß mitochondriale Gene Wachstumsmerkmale von Lämmern über den mitochondrialen Energiestoffwechsel beeinflussen könnten.
Journal of Animal Breeding and Genetics - Tập 112 Số 1-6 - Trang 381-390 - 1995
Genetic contributions and their optimization Summary Genetic contributions were first formalized in 1958 by James and McBride (Journal of Genetics , 56 , 55–62) and have since been shown to provide a unifying framework for theories of gain and inbreeding. As such they have underpinned the development of methods that provide the most effective combination of maximizing gain whilst managing inbreeding and loss of genetic variation. It is shown how this optimum contribution technology can be developed from theory and adapted to provide practical selection protocols for a wide variety of situations including overlapping generations and multistage selection. The natural development of the theory to incorporate genomic selection and genomic control of inbreeding is also shown.
Journal of Animal Breeding and Genetics - Tập 132 Số 2 - Trang 89-99 - 2015
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