کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
8982677 1109171 2005 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Estimates of covariance functions for growth of Nelore cattle applying a parametric correlation structure to model within-animal correlations
موضوعات مرتبط
علوم زیستی و بیوفناوری علوم کشاورزی و بیولوژیک علوم دامی و جانورشناسی
پیش نمایش صفحه اول مقاله
Estimates of covariance functions for growth of Nelore cattle applying a parametric correlation structure to model within-animal correlations
چکیده انگلیسی
A total of 20,065 weights recorded on 3016 Nelore animals were used to estimate covariance functions for growth from birth to 630 days of age, assuming a parametric correlation structure to model within-animal correlations. The model of analysis included fixed effects of contemporary groups and age of dam as quadratic covariable. Mean trends were taken into account by a cubic regression on orthogonal polynomials of animal age. Genetic effects of the animal and its dam and maternal permanent environmental effects were modelled by random regressions on Legendre polynomials of age at recording. Changes in direct permanent environmental effect variances were modelled by a polynomial variance function, together with a parametric correlation function to account for correlations between ages. Stationary and nonstationary models were used to model within-animal correlations between different ages. Residual variances were considered homogeneous or heterogeneous, with changes modelled by a step or polynomial function of age at recording. Based on Bayesian information criterion, a model with a cubic variance function combined with a nonstationary correlation function for permanent environmental effects, with 49 parameters to be estimated, fitted best. Modelling within-animal correlations through a parametric correlation structure can describe the variation pattern adequately. Moreover, the number of parameters to be estimated can be decreased substantially compared to a model fitting random regression on Legendre polynomial of age.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Livestock Production Science - Volume 93, Issue 3, May 2005, Pages 213-222
نویسندگان
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