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Báo cáo sinh học: "Mixture model for inferring susceptibility to mastitis in dairy cattle: a procedure for likelihood-based inference"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học thế giới đề tài: Mixture model for inferring susceptibility to mastitis in dairy cattle: a procedure for likelihood-based inference | Genet. Sel. Evol. 36 2004 3-27 INRA EDP Sciences 2004 DOI 10.1051 gse 2003048 3 Original article Mixture model for inferring susceptibility to mastitis in dairy cattle a procedure for likelihood-based inference Daniel Gianola b J0rgen 0DEGẴRDb Bj0rg HERiNGSTADb Gunnar KLEMETSDALb Daniel Sorensenc Per Madsenc Just Jensenc Johann DETiLLEUxd a Department of Animal Sciences University of Wisconsin-Madison Madison WI 53706 USA b Department of Animal Science Agricultural University of Norway P.O. Box 5025 1432 Ảs Norway c Department of Animal Breeding and Genetics Danish Institute of Agricultural Sciences P.O. Box 50 8830 Tjele Denmark d Faculte de Medicine Veterinaire Universite de Liege 4000 Liege Belgium Received 20 March 2003 accepted 27 June 2003 Abstract - A Gaussian mixture model with a finite number of components and correlated random effects is described. The ultimate objective is to model somatic cell count information in dairy cattle and to develop criteria for genetic selection against mastitis an important udder disease. Parameter estimation is by maximum likelihood or by an extension of restricted maximum likelihood. A Monte Carlo expectation-maximization algorithm is used for this purpose. The expectation step is carried out using Gibbs sampling whereas the maximization step is deterministic. Ranking rules based on the conditional probability of membership in a putative group of uninfected animals given the somatic cell information are discussed. Several extensions of the model are suggested. mixture models maximum likelihood EM algorithm mastitis dairy cattle 1. INTRODUCTION Mastitis is an inflammation of the mammary gland associated with bacterial infection. Its prevalence can be as large as 50 e.g. 16 30 . Its adverse economic effects are through a reduction in milk yield an increase in veterinary costs and premature culling of cows 39 . Milk must be discarded due Corresponding author gianola@calshp.cals.wisc.edu 4 D. Gianola et al. to contamination .