TAILIEUCHUNG - Báo cáo sinh học: " Optimum truncation points for independent culling level selection on a multivariate normal distribution, with an application to dairy cattle selection"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Optimum truncation points for independent culling level selection on a multivariate normal distribution, with an application to dairy cattle selection | 185 Genet Sei. Evol. 1989 21 185-198 Elsevier INRA Original article Optimum truncation points for independent culling level selection on a multivariate normal distribution with an application to dairy cattle selection V. Ducrocq and . Colleau Institut National de la Recherche Agronomique Station de Génétique Quantitative etAppliquée Centre de Recherches de Jouy-en-Josas 78350 Jouy-en-Josas France received 1 March 1988 accepted 19 September 1988 Summary Independent culling level selection is often practiced in breeding programs because extreme animals for some particular traits are rejected by breeders or because records on which genetic evaluation is based are collected sequentially. Optimizing these selection procedures for a given overall breeding objective is equivalent to finding the combination of truncation thresholds or culling levels which rnaximizes the expected value of the overall genetic value for selected animals. A general Newton-type algorithm has been derived to perform this maximization for any number of normally distributed traits and when the overall probability of being selected is fixed. Using a powerful method for the computation of multivariate normal probability integrals it has been possible to undertake the numerical calculation of the optimal truncation points when up to 6 correlated traits or stages of selection are considered simultaneously. The extension of this algorithm to the more complex situation of maximizing annual genetic response subject to nonlinear constraints is demonstrated using a dairy cattle model involving milk production and a secondary trait such as type. Consideration is given to three of the four pathways of selection dams of bulls sires of bulls and sires of cows. Independent culling level selection - dairy cattle - multistage selection - genetic gain -multivariate normal distribution Résumé Seuils de troncature optimaux lors d une sélectlon à nlveaux Indépendants sur une distribution multinormale avec une .

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