Detection and modelling of time-dependent QTL in animal populationsMogens S. Lund1, Peter Sorensen1, Per Madsen1 and Florence Jaffrézic2
1 Faculty of Agricultural Sciences, Department of Genetics and Biotechnology, University of Aarhus, Research Center Foulum, P.O. Box 50 8830 Tjele, Denmark
2 UR337 Station de génétique quantitative et appliquée, INRA, 78350 Jouy-en-Josas, France
(Received 2 January 2007; accepted 3 September 2007; published online 27 February 2008)
Abstract - A longitudinal approach is proposed to map QTL affecting function-valued traits and to estimate their effect over time. The method is based on fitting mixed random regression models. The QTL allelic effects are modelled with random coefficient parametric curves and using a gametic relationship matrix. A simulation study was conducted in order to assess the ability of the approach to fit different patterns of QTL over time. It was found that this longitudinal approach was able to adequately fit the simulated variance functions and considerably improved the power of detection of time-varying QTL effects compared to the traditional univariate model. This was confirmed by an analysis of protein yield data in dairy cattle, where the model was able to detect QTL with high effect either at the beginning or the end of the lactation, that were not detected with a simple 305 day model.
Key words: QTL detection / longitudinal data / random regression models
Correspondence and reprints: Mogens.Lund@agrsci.dk
© INRA, EDP Sciences 2008