Genetic Heteroscedasticity for Domestic Animal Traits
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Animal traits differ not only in mean, but also in variation around the mean. For instance, one sire’s daughter group may be very homogeneous, while another sire’s daughters are much more heterogeneous in performance. The difference in residual variance can partially be explained by genetic differences. Models for such genetic heterogeneity of environmental variance include genetic effects for the mean and residual variance, and a correlation between the genetic effects for the mean and residual variance to measure how the residual variance might vary with the mean.
The aim of this thesis was to develop a method based on double hierarchical generalized linear models for estimating genetic heteroscedasticity, and to apply it on four traits in two domestic animal species; teat count and litter size in pigs, and milk production and somatic cell count in dairy cows.
The method developed is fast and has been implemented in software that is widely used in animal breeding, which makes it convenient to use. It is based on an approximation of double hierarchical generalized linear models by normal distributions. When having repeated observations on individuals or genetic groups, the estimates were found to be unbiased.
For the traits studied, the estimated heritability values for the mean and the residual variance, and the genetic coefficients of variation, were found in the usual ranges reported. The genetic correlation between mean and residual variance was estimated for the pig traits only, and was found to be favorable for litter size, but unfavorable for teat count.
Place, publisher, year, edition, pages
Uppsala: Sveriges Lantbruksuniversitet, 2014. , 54 p.
, Acta Universitatis agriculturae Sueciae, ISSN 1652-6880 ; 2014:43
Quantitative genetics, genetic heteroscedasticity of residuals, genetic heterogeneity of environmental variation, genetic heterogeneity of residual variance, double hierarchical generalized linear models, teat count in pigs, litter size in pigs, milk yield in cows, somatic cell count in cows
Animal and Dairy Science Probability Theory and Statistics
Research subject Komplexa system - mikrodataanalys
IdentifiersURN: urn:nbn:se:du-14310ISBN: 978-91-576-8035-8ISBN: 978-91-576-8034-1OAI: oai:DiVA.org:du-14310DiVA: diva2:725229
2014-06-11, Room L, Undervisningsplan 8, Uppsala, 09:15 (English)
Christensen, Ole Fredslund, Senior researcher
Strandberg, Erling, ProfessorRönnegård, Lars, Professor
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