Document Detail


Association between somatic cell count in early lactation and culling of dairy heifers using cox frailty models.
MedLine Citation:
PMID:  15653521     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The association between somatic cell count (SCC) of dairy heifers in early lactation [SCCel; measured between 5 and 14 d in milk (DIM)] and the culling hazard during the first lactation was studied using Cox frailty models. Udder health problems were the culling reason for 10% of the culled heifers in this study. For each unit increase in the log-transformed SCCel (LnSCCel), the culling hazard increased by 11% [Hazard ratio (HR) = 1.11]. The strength of the association depended on 5 factors. Firstly, the association was stronger when SCCel was recorded after 10 DIM than at an earlier DIM. Secondly, the association was stronger if only culling events for udder disorders were considered (HR = 1.32) instead of all culling events (HR = 1.11). Furthermore, for each unit increase of test-day LnSCC after 14 DIM, modeled as a time-varying covariate, the culling hazard in the first lactation increased by 26% (HR = 1.26). Including LnSCC in the model already containing LnSCCel, reduced the estimate of LnSCCel slightly. Fourth, a higher test-day milk yield, modeled as a time-varying covariate, protected against culling and reduced the magnitude of the effect of LnSCCel as well when taken into account. Finally, the association between LnSCCel and culling was still present, although smaller, in the group of heifers with a second test-day SCC </=50,000 cells/mL.
Authors:
S De Vliegher; H W Barkema; G Opsomer; A de Kruif; L Duchateau
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of dairy science     Volume:  88     ISSN:  0022-0302     ISO Abbreviation:  J. Dairy Sci.     Publication Date:  2005 Feb 
Date Detail:
Created Date:  2005-01-17     Completed Date:  2005-03-29     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:  560-8     Citation Subset:  IM    
Affiliation:
Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium. Sarne.Devliegher@UGent.be
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MeSH Terms
Descriptor/Qualifier:
Animals
Cattle / physiology*
Cell Count*
Dairying / methods*
Female
Lactation*
Milk / cytology*
Proportional Hazards Models*
Time Factors

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


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