It is difficult to evaluate the genetic performance for longevity, because the complete information on longevity cannot be obtained until disposal.  Since some cows are still alive at the time of genetic evaluation, the information on longevity are censored at earlier stage.  To exclude the censored records in the analysis would lead to biased results.  Vukasinovic et al. (1999) showed that the rank correlations of the estimated transmitting abilities of sires from the data with censored records and from the reference data decreased with increasing proportion of censored records.  However, the effect of periods of data collection for genetic evaluation on longevity has not been reported. 

O. Sasaki, K. Ishii, H. Takeda

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 2002. Session 1, , 1.76, 2002
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