Document Detail


Genetic components of days open under heat stress.
MedLine Citation:
PMID:  15375064     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
A reaction norm approach was used to estimate the genetic parameters of days open (DO) with a model that accounted for heat stress. Data included DO records for Georgia, Tennessee, and North Carolina in the Southeastern United States. A fixed effect model included herd-year, month of calving (MOC), age of cow, and a regression on 305-d milk yield. The reaction norm model additionally included the effect of animal with random regression on a heat stress index (HI), calculated as the standardized solutions to MOC derived from the fixed effect model; the residual variance was assumed to be a function of the HI. The shape of the distribution of the HI was close to a sinusoidal function with the highest value in March/April and the lowest value in September. Genetic and residual variances and heritabilities were highest for spring calvings and lowest for fall calvings. The variance associated with the random regression of the highest level of HI was 33% of the genetic variance of the regular animal genetic effect. Genetic correlation between these effects was 0.67. As a validation, DO data were grouped into 4 seasons of calving and treated as different traits. A 4-trait mixed linear model that included the fixed effects listed above except MOC, was used to analyze the grouped data. In general, the estimates of genetic and residual variances of the multiple trait analyses followed those of the reaction norm model. Genetic correlations of spring with summer, and fall with winter were both 0.90. Genetic correlations between spring/summer and fall/winter were around 0.80. The reaction norm model for DO allows inexpensive genetic evaluation of fertility under heat stress. Results of such an evaluation may strongly depend on editing criteria and model specifications.
Authors:
S Oseni; I Misztal; S Tsuruta; R Rekaya
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of dairy science     Volume:  87     ISSN:  0022-0302     ISO Abbreviation:  J. Dairy Sci.     Publication Date:  2004 Sep 
Date Detail:
Created Date:  2004-09-17     Completed Date:  2004-11-23     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  2985126R     Medline TA:  J Dairy Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3022-8     Citation Subset:  IM    
Affiliation:
Department of Animal and Dairy Science, The University of Georgia, Athens 30602-2771, USA.
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MeSH Terms
Descriptor/Qualifier:
Analysis of Variance
Animals
Cattle / genetics*
Cattle Diseases / genetics*
Female
Genetic Variation
Heat Stress Disorders / genetics,  veterinary*
Lactation*
Pregnancy
Regression Analysis
Seasons

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


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