The objective of this study was to assess the relationship between reproductive traits and functional longevity of Isfahan dairy herds using survival analysis. Data consisted of 82,505 daughter’s life records of 1952 sires calving between 2001 and 2016. Functional longevity was defined as the number of days from first calving to last known test day record. The piecewise Wiebull baseline hazard function with 25 different hazard functions were defined for each combination of lactation (1 to 5) and stage of lactation (1 to 5). The model included the time-dependent fixed effects of withi herd-year-lactation Key Words Survival analysis, Functional longevity, Reproductive traits, Nongenetic effects, Holstein cows
