Abstract
Optimising the number of replacement heifers needed will have positive economic and environmental consequences on herds that rear their own young stock. The number of heifers needed to be kept is 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 defined for each year as percentage of the herd size that died within 30d after they were culled. The analysis of the association between average culling rate for slaughter/death and the characteristics of the herd was performed using a mixed model. 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 have 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 is associated with a longer average calving interval, a higher average 305-d protein production, a higher average somatic cell count (SCC), a higher percentage of new high SCC, 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 is 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 is associated with fertility, udder health and openness of the herd.
Highlights
Most Dutch dairy herds rear their own replacement heifers
The herds are representative for Dutch dairy herds as they were randomly selected and the average herd size is comparable to the Dutch population average (CRV, 2010)
The results showed that the average overall culling rate and the average culling rate for slaughter/death are higher than those reported in the UK (Whitaker et al 2004), similar to the culling rates reported previously in the Netherlands, France and Poland (Sol et al 1984; Olechnowicz & Jaskowski, 2011; Raboisson et al 2011) and lower than the annual culling rate in the United States (De Vries et al 2010)
Summary
Most Dutch dairy herds rear their own replacement heifers. The costs of rearing them range from E1400 to E1700 per heifer (Mohd Nor et al 2012). Culling a dairy cow was found to be associated with reproductive status and disorders (Stevenson & Lean, 1998; Schneider et al 2007; De Vries et al 2010), milk yield (Pinedo et al 2010) and health related conditions such as ketosis, milk fever, retained placenta, metritis, lameness, teat injuries and mastitis (Gröhn et al 1998; Rajala-Schultz & Gröhn, 1999a; Chiumia et al 2013). These associations are known to differ with variation in age, parity and stage. The second objective was to determine the association between the average culling rate for slaughter/death over the years 2007 to 2010 with herd characteristics (e.g. herd size), herd reproduction characteristics (e.g. calving interval and first calving age), herd performance characteristics (e.g. 305-d milk, protein and fat production, lifetime milk production and age) and herd health characteristics (e.g. average SCC and percentage of dairy cows with claw problems)
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