The average culling rate of Dutch dairy herds over the years 2007 to 2010 and its association with herd reproduction, performance and health

If the number of replacement heifers can be optimized, it may have positive genetic, economic and environmental consequences for the enterprise. These influences are sometimes opposing. For example, in a herd that is genetically upgraded superior heifer genetic material will be beneficial to the longer term economy. A lower replacement rate, however, will be beneficial to the economy because herd yield is maximized over the shorter term and to the environment as less methane will be produced per kg milk, if the herd otherwise remain constant. The question of optimum replacement remains intriguing. Dr Nora and co-workers, therefore, decided to investigate the replacement status in The Netherlands. They published their results in the Journal of Dairy Research, Volume 81 of 2014, pages 1 to 8, with the title: The average culling rate of Dutch dairy herds over the years 2007 to 2010 and its association with herd reproduction, performance and health.

The number of heifers needed to be kept is normally closely related with the number of culled dairy cows in the herd. This study therefore looked at the variation that exists in culling rate and herd level factors associated with it. A dataset from 1903 dairy herds available included information at animal level (dates of culling, slaughter/death) and herd level (characteristics of reproduction, performance, health) over the years 2007 to 2010. The average culling rate for slaughter/death was used and was calculated for each year as percentage of the herd size that died within 30 days after they were culled. The association between average culling rate for slaughter/death and the characteristics of the herd was statistically analysed.

The results showed that the average culling rate for slaughter/death was 25.4% and varied between 23% (2007) and 28% (2010). More than 70% of the herds had an average culling rate for slaughter/death of less than 30%, showing that there is room for lowering the average culling rate for slaughter/death. A higher average culling rate for slaughter/death was associated with a longer average calving interval, a higher average 305-day protein (and milk yield) production, a higher average somatic cell count (SCC), a higher percentage of new high SCC’s, a more than 5% decrease in herd size, and herds that bought more than 1% of animals per year. A lower average culling rate for slaughter/death was associated with a longer average age, herds that bought less than 1% of animals per year and a more than 5% increase in herd size.

In conclusion, the average culling rate for slaughter/death was associated with fertility, udder health and openness of the herd. The results show positives both ways; the decision of a higher or lower culling rate therefore depends on the particular circumstances on the farm. The results obtained in the study should be useful as guidelines to decide.