Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học quốc tế đề tài: Genetic parameters for social effects on survival in cannibalistic layers: Combining survival analysis and a linear animal model | Ellen et al. Genetics Selection Evolution 2010 42 27 http content 42 1 27 GSE Ge n et i cs Selection Evolution RESEARCH Open Access Genetic parameters for social effects on survival in cannibalistic layers Combining survival analysis and a linear animal model Esther D Ellen1 Vincent Ducrocq2 Bart J Ducro1 Roel F Veerkamp3 Piter Bijma1 Abstract Background Mortality due to cannibalism in laying hens is a difficult trait to improve genetically because censoring is high animals still alive at the end of the testing period and it may depend on both the individual itself and the behaviour of its group members so-called associative effects social interactions . To analyse survival data survival analysis can be used. However it is not possible to include associative effects in the current software for survival analysis. A solution could be to combine survival analysis and a linear animal model including associative effects. This paper presents a two-step approach 2STEP combining survival analysis and a linear animal model including associative effects LAM . Methods Data of three purebred White Leghorn layer lines from Institut de Sélection Animale . a Hendrix Genetics company were used in this study. For the statistical analysis survival data on 16 780 hens kept in four-bird cages with intact beaks were used. Genetic parameters for direct and associative effects on survival time were estimated using 2STEP. Cross validation was used to compare 2STEP with LAM. LAM was applied directly to estimate genetic parameters for social effects on observed survival days. Results Using 2STEP total heritable variance including both direct and associative genetic effects expressed as the proportion of phenotypic variance ranged from 32 to 64 . These results were substantially larger than when using LAM. However cross validation showed that 2STEP gave approximately the same survival curves and rank correlations as LAM. Furthermore cross validation showed that .
