Different aspects of survival analysis applied to dairy cows have been discussed in the literature, but in most cases the reason for failure is not taken into consideration. When failure reasons are of interest and must be accounted for in the analysis, the method of competing risks (Kalbfleisch and Prentice, 1980) offers an intuitive but powerful way of handling survival times. The general concept underlying competing risks analysis is that the occurrence of one type of event removes the individual from risk of all other types of events. In this case, the overall hazard function is the sum of all the type-specific hazards, which can be obtained in the same way as the regular hazard function, just regarding all failures of types other than the recorded reason for failure as censored at the individual’s failure time (Allison, 1995). The competing risks approach is of particular interest in the study of reasons for disposal in dairy cattle. Cows being culled for different reasons were certainly affected by a distinct set of covariates or by the same covariates in different degrees (Dürr et al., 1997), and modeling their hazards in a competing risks framework seems to be a very appropriate approach.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 2002. Session 1, , 1.27, 2002
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