Analysis of mortality and culling in first three parities of Holstein cows in three regions of US
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In order to investigate the seasonal patterns of mortality and culling, and the relationship between 305-days milk yield and those two traits, termination codes from Dairy Herd Improvement (DHI) were used to define mortality and culling, for the analysis. The records from 1999 to 2008 were obtained from US Holstein cows in first three parities in the Southeast, Southwest, and Northeast of United States. Higher mortality and culling rate in summer indicated that heat stress may be one of the possible factors that cause health, reproduction, and production related problems. Low estimated heritability showed the difficulty on improvement in these traits by selection. However, positive correlation between mortality and 305-days milk yield denoted that high milk production could be an indicator of high risk of mortality. Also, negative correlation between culling and milk production indicated preferential veterinary care on high milk producing cows.