Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học thế giới đề tài: Cumulative t-link threshold models for the genetic analysis of calving ease scores | 489 Genet Sei. Evol. 35 2003 489-512 INRA EDP Sciences 2003 DOI gse 2003036 Original article Cumulative t-link threshold models for the genetic analysis of calving ease scores Kadir Kizilkayaa Paolo Carnierb Andrea Alberac Giovanni Bittanteb Robert J. Tempelmana a Department of Animal Science Michigan State UniversitY East Lansing 48824 USA b Department of Animal Science UniversitY of Padova Agripolis 35020 Legnaro ItalY c Associazione Nazionale Allevatori Bovini di Razza Piemontese Strada Trinità 32a 12061 Carrù ItalY Received 24 June 2002 accepted 10 March 2003 Abstract - In this study a hierarchical threshold mixed model based on a cumulative i-link specification for the analysis of ordinal data or more specifically calving ease scores was developed. The validation of this model and the Markov chain Monte Carlo MCMC algorithm was carried out on simulated data from normally and Í4 . a i-distribution with four degrees of freedom distributed populations using the deviance information criterion DIC and a pseudo Bayes factor PBF measure to validate recently proposed model choice criteria. The simulation study indicated that although inference on the degrees of freedom parameter is possible MCMC mixing was problematic. Nevertheless the Die and PBF were validated to be satisfactory measures of model fit to data. A sire and maternal grandsire cumulative i-link model was applied to a calving ease dataset from 8847 Italian Piemontese first parity dams. The cumulative Í4-link model was shown to lead to posterior means of direct and maternal heritabilities and a direct maternal genetic correlation that were not different from the corresponding posterior means of the heritabilities and the genetic correlation inferred under the conventional cumulative probit link threshold model. Furthermore the correlation between posterior means of sire progeny merit from the two models suggested no meaningful .
