The aim of the study was to carry out survival analysis to evaluate fixed effects and to estimate genetic parameters on survival of laying hens. The data set contained 16,694 records of three purebred White Leghorn layer lines coded W1, WB and WF. At 17 weeks old after rearing, hens were transported to two laying stables and were randomly assigned to traditional 4–birds battery cages. Censoring status i.e. alive or dead was recorded. The traits studied were overall survival during the entire laying period (17 to 64 weeks of age), survival in the early production period (17 to 40 weeks of age) and survival in late production period (41 to 64 weeks of age). The results showed all fixed effects in the model i.e. stable by corridor interaction effect, mortality of back cage neighbors, level and layer lines were highly significant. Overall survival during the entire laying period was 60.4 % while survival during early laying period was 85.1 % and survival in the late laying period was 70.9%. Different risk ratio patterns were observed between the two laying stables. Hens in the top row had about 20% higher risk of death. Number of death cases in the back neighbor cage had a negative effect on the survival. Highest risk of death for line WB and lowest risk for line WF were found. Heritability for survival traits ranged from 0.04 to 0.15. This indicates genetic improvement is possible. Genetic correlation between overall survival and early laying period and between overall survival and late were high, indicating positive correlated response through selection.
- Laying hens
- Survival analysis