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Genetic evaluation of clinical mastitis in dairy cattle

Carlén, Emma (2008). Genetic evaluation of clinical mastitis in dairy cattle. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2008:63
ISBN 978-91-85913-96-1
[Doctoral thesis]

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This thesis aims to advance our understanding of the genetic background of mastitis resistance in dairy cattle. More particularly, it seeks to improve the potential of genetic evaluation of clinical mastitis (CM) both by utilizing more of the available information and by applying appropriate methodology. A linear cross-sectional model was used to estimate genetic parameters for binary CM, somatic cell count (SCC) and milk production in the first three lactations of Swedish Holstein cows. The unfavorable genetic correlations found between udder health and production traits emphasize the need to include mastitis resistance in the breeding goal. The higher heritability of SCC (0.10-0.14) than CM (0.01-0.03) and the high genetic correlation between these two traits (average 0.70) imply that SCC is a useful indicator trait in breeding for improved mastitis resistance. The method of survival analysis was used to analyze time to first CM and was compared with a linear cross-sectional model on field data and with linear and threshold cross-sectional models in a simulation study. Despite the theoretical advantages of survival analysis, there was no difference in the accuracy of genetic evaluation when methods were compared within the same length of opportunity period. The correlation between true and predicted sire breeding values in the simulation study was, however, 8% greater when data from the full lactation rather than the first 150 days were used. Longitudinal binary CM data in 12 intervals of first lactation were analyzed as repeated observations in a linear random regression model. This method has some appealing features so far as genetic evaluation of CM is concerned, but it was found rather sensitive for parameter estimation in the current setting. Genetic parameters from the chosen random regression model agreed rather well, however, with the corresponding estimates from a linear longitudinal multivariate model in which records of CM in the different intervals were considered as different traits. Both longitudinal models indicated clearly that CM is not the same trait genetically throughout lactation, something that is ignored in a cross-sectional model.

Authors/Creators:Carlén, Emma
Title:Genetic evaluation of clinical mastitis in dairy cattle
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2008
Number of Pages:63
ALLI Carlén, E., Strandberg, E. and Roth, A. 2004. Genetic parameters for clinical mastitis, somatic cell score, and production in the first three lactations of Swedish Holstein cows. Journal of Dairy Science 87, 3062-3070. II Carlén, E., Schneider, M. del P. and Strandberg, E. 2005. Comparison between linear models and survival analysis for genetic evaluation of clinical mastitis in dairy cattle. Journal of Dairy Science 88, 797-803. III Carlén, E., Emanuelson, U. and Strandberg, E. 2006. Genetic evaluation of mastitis in dairy cattle using linear models, threshold models, and survival analysis: A simulation study. Journal of Dairy Science 89, 4049-4057. IV Carlén, E., Grandinson, K., Emanuelson, U. and Strandberg, E. 2008. Random regression models for genetic evaluation of clinical mastitis in dairy cattle. Submitted.
Place of Publication:Uppsala
ISBN for printed version:978-91-85913-96-1
Publication Type:Doctoral thesis
Full Text Status:Public
Agrovoc terms:dairy cattle, mastitis, evaluation, linear models, survival, statistical methods, heritability, genetic correlation
Keywords:dairy cattle, clinical mastitis, genetic evaluation, linear model, survival analysis, random regression model, longitudinal model, heritability, genetic correlation, breeding value prediction
Permanent URL:
ID Code:1836
Department:(VH) > Dept. of Animal Breeding and Genetics
Deposited By: Emma Carlén
Deposited On:01 Oct 2008 00:00
Metadata Last Modified:02 Dec 2014 10:14

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