Genet. Sel. Evol.
Volume 40, Number 3, May-June 2008
|Page(s)||295 - 308|
|Published online||10 April 2008|
Data transformation for rank reduction in multi-trait MACE model for international bull comparisonJoaquim Tarres1, 2, Zengting Liu1, Vincent Ducrocq2, Friedrich Reinhardt1 and Reinhard Reents1
1 VIT, Heideweg 1, 29283 Verden, Germany
2 UR337, Station de génétique quantitative et appliquée, INRA, 78352 Jouy-en-Josas Cedex, France
(Received 19 March 2007; accepted 5 November 2007 ; published online 10 April 2008)
Abstract - Since many countries use multiple lactation random regression test day models in national evaluations for milk production traits, a random regression multiple across-country evaluation (MACE) model permitting a variable number of correlated traits per country should be used in international dairy evaluations. In order to reduce the number of within country traits for international comparison, three different MACE models were implemented based on German daughter yield deviation data and compared to the random regression MACE. The multiple lactation MACE model analysed daughter yield deviations on a lactation basis reducing the rank from nine random regression coefficients to three lactations. The lactation breeding values were very accurate for old bulls, but not for the youngest bulls with daughters with short lactations. The other two models applied principal component analysis as the dimension reduction technique: one based on eigenvalues of a genetic correlation matrix and the other on eigenvalues of a combined lactation matrix. The first one showed that German data can be transformed from nine traits to five eigenfunctions without losing much accuracy in any of the estimated random regression coefficients. The second one allowed performing rank reductions to three eigenfunctions without having the problem of young bulls with daughters with short lactations.
Key words: rank reduction / principal components / genetic correlation matrix / multiple across country evaluation / dairy cattle
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© INRA, EDP Sciences 2008