Standardized analysis of German cattle mortality using national register data

Abstract

In a retrospective cohort study of national register data, 1946 randomly selected holdings, with 286,912 individual cattle accumulating 170,416 animal-years were analyzed. The sample was considered to represent the national herd in Germany 2012. Within each holding, individual cattle records were stratified by current age (≤21 days, 3–6 weeks, 6–12 weeks, 3–6 months, 6–12 months, 1–2, 2–4, 4–8, and >8 years), sex, breed (intensive milk, less intensive milk, and beef), and mean monthly air temperature (<10°C and ≥10°C). Holdings were categorized by size (<100 and ≥100 animal-years), calving rate, slaughter rate, and federal state. 8027 on-site deaths (excluding slaughter for human consumption) were recorded, with cattle aged <6 months, 6–24 months, and >2 years contributing 50.0%, 15.4%, and 34.6% of deaths, respectively. Poisson regression and generalized estimating equations (gee) accounting for intra-herd clustering were used to model the number of deaths. In both models, most age bands differed significantly, with highest rates in calves ≤21 days, falling to lowest rates in 1–2 year olds, and rising again thereafter in females. Males exhibited higher mortality than females from birth to 2 years. All breed categories differed significantly with lowest rates in beef and highest in intensive milk breeds. Larger holdings, temperatures ≤10°C, calving rates >0–0.5 per animal year were all associated with higher mortality. Via interaction, intensive and less intensive milk breed cattle aging 6 weeks to 6 months and intensive milk breed females >4 years were associated with higher mortality. There were no significant differences between federal states and slaughter rates. The standardized deviations of modeled dead cattle numbers from occurred deaths per calendar year per holding were calculated and a 95% reference range of deviations constructed. This approach makes a standardized active monitoring and surveillance system regardless of herd size possible, offering a useful, inexpensive and easy implementable aid in the detection of holdings deviant from mortality levels of the national herd.