tailieunhanh - Báo cáo sinh học: " Validation of models for analysis of ranks in horse breeding evaluation"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học quốc tế đề tài: Validation of models for analysis of ranks in horse breeding evaluation | Ricard and Legarra Genetics Selection Evolution 2010 42 3 http content 42 1 3 GSE Ge n et i cs Selection Evolution RESEARCH Open Access Validation of models for analysis of ranks in horse breeding evaluation Anne Ricard 1 Andrés Legarra2 Abstract Background Ranks have been used as phenotypes in the genetic evaluation of horses for a long time through the use of earnings normal score or raw ranks. A model underlying model of an unobservable underlying variable responsible for ranks exists. Recently a full Bayesian analysis using this model was developed. In addition in reality competitions are structured into categories according to the technical level of difficulty linked to the technical ability of horses horses considered to be the best meet their peers . The aim of this article was to validate the underlying model through simulations and to propose a more appropriate model with a mixture distribution of horses in the case of a structured competition. The simulations involved 1000 horses with 10 to 50 performances per horse and 4 to 20 horses per event with unstructured and structured competitions. Results The underlying model responsible for ranks performed well with unstructured competitions by drawing liabilities in the Gibbs sampler according to the following rule the liability of each horse must be drawn in the interval formed by the liabilities of horses ranked before and after the particular horse. The estimated repeatability was the simulated one and regression between estimated competing ability of horses and true ability was close to 1. Underestimations of repeatability to were obtained with other traditional criteria normal score or raw ranks but in the case of a structured competition repeatability was underestimated to . Our results show that the effect of an event or category of event is irrelevant in such a situation because ranks are independent of such an effect. The proposed mixture model pools horses