Document Detail

Impact of selection on components of variance and heritabilities of Canadian Holstein conformation traits.
MedLine Citation:
PMID:  3624597     Owner:  NLM     Status:  MEDLINE    
Sire and error variance components and heritabilities were estimated for 26 conformation traits using linear type classifications of 175,693 daughters of 6681 Holstein sires in 21,869 herd-round-classifier subclasses. Estimates from first classifications during first lactations were contrasted with estimates from the same 175,693 females' most recent classification, which included reclassifications. Only cows that have their final classification raised a full category receive an official reclassification record; thus, heritability estimates from data that include these reclassification records may be biased. A total of 9420 (5.4%) of the first lactation, first classifications were replaced by reclassifications for the second analysis, which is current practice for official sire evaluations for Holsteins in Canada. Records, expressed as Snell's scores, were preadjusted for age within parity and stage of lactation at classification. Sire and error components of variance were estimated by Henderson's new method. When reclassifications replaced first classifications in the analysis, estimates of sire and error variances increased 7.2 and 11.1% respectively, as compared with the first lactation, first classification estimates. Heritabilities ranged from .07 for rear heel to .38 for stature and decreased by an average of 2.5% when first lactation, first classifications were replaced by reclassifications. Results indicate that the inclusion of reclassifications tends to bias heritabilities downward.
B J Van Doormaal; E B Burnside
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of dairy science     Volume:  70     ISSN:  0022-0302     ISO Abbreviation:  J. Dairy Sci.     Publication Date:  1987 Jul 
Date Detail:
Created Date:  1987-09-29     Completed Date:  1987-09-29     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  2985126R     Medline TA:  J Dairy Sci     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1452-7     Citation Subset:  IM    
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MeSH Terms
Body Constitution*
Cattle / genetics*
Genetic Variation*
Selection, Genetic*

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

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