2009-Costard_et_al - A dynamic deterministic model to...

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A. D. Costard, Z. G. Vitezica, C. R. Moreno and J.-M. Elsen A dynamic deterministic model to optimize a multiple-trait selection scheme doi: 10.2527/jas.2008-0898 originally published online November 21, 2008 2009, 87:885-894. J ANIM SCI http://jas.fass.org/content/87/3/885 the World Wide Web at: The online version of this article, along with updated information and services, is located on www.asas.org by guest on October 11, 2011 jas.fass.org Downloaded from
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ABSTRACT: A mathematical approach was devel- oped to model and optimize simultaneous selection on 2 traits, a quantitative trait with underlying polygenic variation and a monogenic trait (e.g., resistance to a disease). A deterministic model allows global optimiza- tion of the selection scheme to maximize the frequency of the desired genotype for the monogenic trait, while minimizing the loss of genetic progress on the polygenic trait. An additive QTL or gene was considered. Breed- ing programs with overlapping generations, different se- lection strategies for males and females, and assortative mating were modeled. A genetic algorithm was used to solve this optimization problem. This modeling ap- proach may easily be adapted to a variety of underlying genetic models and selection schemes. This model was applied to an example where selection on the Prp gene for scrapie resistance was introduced as an additional selection criterion in an already existing dairy sheep selection scheme. Key words: genetic algorithm, global optimization, marker-assisted selection, selection scheme ©2009 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2009. 87:885–894 doi:10.2527/jas.2008-0898 INTRODUCTION Gene or QTL information could improve selection efficiency and allow the implementation of marker- assisted selection. Marker-assisted selection has been proposed to improve classical selection schemes for complex traits with low heritability or that are difficult or expensive to measure (Lande and Thompson, 1990; Meuwissen and van Arendonk, 1992; Dekkers and van Arendonk, 1998). Strategies to use QTL or gene infor- mation in marker-assisted selection are mainly based on indices combining the EBV for QTL and the EBV for the residual polygenic effect. Marker-assisted selec- tion increases the QTL frequency in the short-term, but can result in less response in the long-term (Lande and Thompson, 1990). Several studies (Gibson, 1994; Larzul et al., 1997b; Pong-Wong and Woolliams, 1998) have explored the interactions between selection meth- ods and time horizon. Dekkers and van Arendonk (1998) optimized selection on an identified QTL in a simple se- lection scheme (phenotypic selection, random mating) using an optimal control approach (Lewis, 1986). The method was extended by Chakraborty et al. (2002). The benefit of optimal selection on a single identified QTL and the differences between optimal and standard QTL selection were evaluated by Dekkers and Chakraborty (2001). Manfredi et al. (1998) optimized selection and mating on a QTL for a sex-limited trait using sequen- tial quadratic programming. In these studies, selection
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2009-Costard_et_al - A dynamic deterministic model to...

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