TAILIEUCHUNG - Báo cáo sinh học: " Exploration of lagged relationships between mastitis and milk yield in dairy cows using a Bayesian structural equation Gaussian-threshold model"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học thế giới đề tài: Exploration of lagged relationships between mastitis and milk yield in dairy cows using a Bayesian structural equation Gaussian-threshold model | Genet. Sel. Evol. 40 2008 333-357 Available online at INRA EDP Sciences 2008 DOI gse 2008009 Original article Exploration of lagged relationships between mastitis and milk yield in dairy cows using a Bayesian structural equation Gaussian-threshold model Xiao-Lin Wu1 Bjerg Heringstad2 Daniel Gianola1 2 3 department of Dairy Science University of Wisconsin Madison WI 53706 USA department of Animal and Aquacultural Sciences Norwegian University of Life Sciences 1432 As Norway 3Department of Animal Sciences and Department of Biostatistics and Medical Bioinformatics University of Wisconsin Madison WI 53706 USA Received 17 May 2007 accepted 15 January 2008 Abstract - A Gaussian-threshold model is described under the general framework of structural equation models for inferring simultaneous and recursive relationships between binary and Gaussian characters and estimating genetic parameters. Relationships between clinical mastitis CM and test-day milk yield MY in first-lactation Norwegian Red cows were examined using a recursive Gaussian-threshold model. For comparison the data were also analyzed using a standard Gaussian-threshold a multivariate linear model and a recursive multivariate linear model. The first 180 days of lactation were arbitrarily divided into three periods of equal length in order to investigate how these relationships evolve in the course of lactation. The recursive model showed negative within-period effects from liability to CM to test-day MY in all three lactation periods and positive between-period effects from test-day MY to liability to CM in the following period. Estimates of recursive effects and of genetic parameters were time-dependent. The results suggested unfavorable effects of production on liability to mastitis and dynamic relationships between mastitis and test-day MY in the course of lactation. Fitting recursive effects had little influence on the estimation of genetic parameters. However some differences .

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