Simultane Zuchtwertschätzung mit Reinzucht- und Kreuzungsleistungen unter Dominanz

Abstract. Title of the paper: Joint genetic evaluation of purebred and crossbred data under dominance
Currently available Software packages are not able to handle the Joint genetic evaluation of pure and crossbred data correctly. Instead, the same traits originating in the two purebreds and the crossbred are treated as three separate traits and analysed in a three trait animal model. Using selection index theory it can be demonstrated that this procedure contains model violations even if only additive genetic effects are considered. The effectiveness of the correct model which allows different contributions of the parental lines to the genetic variance of the cross including animal specific dominance effects is assessed on the basis of different selection indices. The sources of information chosen reflect those available in typical chicken breeding programs. The genetic parameters required for index construction – in particular the dominance variance and the genetic correlation between the pure and cross breds – were derived using a two locus model. If the purebred contribute extremely differently to the crossbred variance large losses in efficiency can be observed. With contributions of the sire line of 11, 19, 37 and 40% to the additive genetic variance of the cross corresponding losses in efficiency of selection where 13.1, 6.5, 0.6 and 0.2% respectively. Not considering the dominance variance – depending on its proportion relative to the total genetic variance – lead to a moderate loss of efficiency from 0.1 to 2.6%.