Document Detail

The use of covariance functions and random regressions for genetic evaluation of milk production based on test day records.
MedLine Citation:
PMID:  9891276     Owner:  NLM     Status:  MEDLINE    
In the analysis of test day records for dairy cattle, covariance functions allow a continuous change of variances and covariances of test day yields on different lactation days. The equivalence between covariance functions as an infinite dimensional extension of multivariate models and random regression models is shown in this paper. A canonical transformation procedure is proposed for random regression models in large-scale genetic evaluations. Two methods were used to estimate covariance function coefficients for first parity test day yields of Holsteins: 1) a two-step procedure fitting covariance functions to matrices with estimated genetic and residual covariances between predetermined periods of lactation and 2) REML directly from data with a random regression model. The first method gave more reliable estimates, particularly for the periphery of the trajectory. The goodness of fit of a random regression model based on covariables describing the shape of the lactation curve was nearly the same as random regression on Legendre polynomials. In the latter model, two and three regression coefficients were sufficient to fit the covariance structure for additive genetic and permanent environment, respectively. The eigenfunction pattern revealed the possibility of selection for persistency. Covariance functions can be usefully implemented in large-scale test day models by means of random regressions.
J H van der Werf; M E Goddard; K Meyer
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of dairy science     Volume:  81     ISSN:  0022-0302     ISO Abbreviation:  J. Dairy Sci.     Publication Date:  1998 Dec 
Date Detail:
Created Date:  1999-03-11     Completed Date:  1999-03-11     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985126R     Medline TA:  J Dairy Sci     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  3300-8     Citation Subset:  IM    
Animal Genetics and Breeding Unit, University of New England, Armidale, New South Wales, Australia.
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MeSH Terms
Analysis of Variance*
Cattle / genetics*
Lactation / genetics*
Models, Genetic
Regression Analysis*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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