فهرست نشریات علمی دسترسی آزاد ایران

This study was carried out in a commercial herd from 2008 to 2012 in order to determine the most prevalent reasons for culling Holstein cows and to assess the effects of risk factors. Overall, 519 (28.2%) cows were culled for involuntary (98.8%) and voluntary (1.2%) reasons. The involuntary causes of culling were diseases (38.7%), reproduction problems (36.0%), udder disorders (7.7%), lameness (3.7%) and death (12.7%). Mean age of cows at culling was 70.5±15.6 months and the time interval from last calving to culling averaged 263±196 days. Logistic binary regression was used to model the hazard of culling. The analysis of risk factors showed that parity, calving season, and age at first calving had significant effects on the hazard of culling (P < 0.05 to P