Document Detail

Parametric correlation functions to model the structure of permanent environmental (co)variances in milk yield random regression models.
MedLine Citation:
PMID:  19700726     Owner:  NLM     Status:  MEDLINE    
The objective of the present study was to estimate milk yield genetic parameters applying random regression models and parametric correlation functions combined with a variance function to model animal permanent environmental effects. A total of 152,145 test-day milk yields from 7,317 first lactations of Holstein cows belonging to herds located in the southeastern region of Brazil were analyzed. Test-day milk yields were divided into 44 weekly classes of days in milk. Contemporary groups were defined by herd-test-day comprising a total of 2,539 classes. The model included direct additive genetic, permanent environmental, and residual random effects. The following fixed effects were considered: contemporary group, age of cow at calving (linear and quadratic regressions), and the population average lactation curve modeled by fourth-order orthogonal Legendre polynomial. Additive genetic effects were modeled by random regression on orthogonal Legendre polynomials of days in milk, whereas permanent environmental effects were estimated using a stationary or nonstationary parametric correlation function combined with a variance function of different orders. The structure of residual variances was modeled using a step function containing 6 variance classes. The genetic parameter estimates obtained with the model using a stationary correlation function associated with a variance function to model permanent environmental effects were similar to those obtained with models employing orthogonal Legendre polynomials for the same effect. A model using a sixth-order polynomial for additive effects and a stationary parametric correlation function associated with a seventh-order variance function to model permanent environmental effects would be sufficient for data fitting.
A B Bignardi; L El Faro; V L Cardoso; P F Machado; L G Albuquerque
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of dairy science     Volume:  92     ISSN:  1525-3198     ISO Abbreviation:  J. Dairy Sci.     Publication Date:  2009 Sep 
Date Detail:
Created Date:  2009-08-24     Completed Date:  2009-11-30     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985126R     Medline TA:  J Dairy Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  4634-40     Citation Subset:  IM    
Department of Animal Science, São Paulo State University (FCAV/UNESP), Jaboticabal, SP, Brazil.
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MeSH Terms
Cattle / genetics,  physiology*
Lactation / genetics*
Milk / secretion*
Models, Biological*
Quantitative Trait, Heritable
Regression Analysis

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