Using slaughterhouse findings to monitor animal health and welfare is not a new idea. The German Federal Veterinary Surgeon's Association even calls for the establishment of an animal health database that combines slaughterhouse findings with health and farm data from already existing monitoring programs to create a comprehensive monitoring and surveillance tool. In an attempt to combine secondary health data from slaughterhouse findings, antibiotic use monitoring as well as biosecurity and husbandry evaluations into an integrated dataset, data from 18,593 fattening pig farms across Germany participating in the private sector Quality scheme for food (from 2018 to 2020) were harmonized at the half-year level and combined. As an example, the combined data was used to evaluate lung and tail lesion findings from abattoirs as indicators of animal health and welfare with descriptive analysis and mixed model approaches. Differences between abattoirs due to different data collection methods were taken into account by either considering the abattoir as a random effect or standardizing the prevalence data using abattoir means. The mean prevalence of lung lesions per halfyear varied between 8.69 % and 9.78 %. The mean prevalence of tail lesion increased continuously from 0.65 % in the first half of 2018-1.04 % in the second half of 2020. Farm size, agricultural region, half-year and antibiotic treatment frequency were found to be associated (p <0.000001) with the prevalence of both lung and tail lesions. A lack of variance and specificity of the secondary biosecurity and husbandry evaluation data restricts the use of individual assessment criteria as well as biosecurity and husbandry indices (calculated from a subset of assessment criteria) in our analyses. We therefore used the data for a broad categorization of farms and it could be found, that the occurrence of a lower rating in any assessment criteria during farm evaluations is associated (p <0.000001) with a higher prevalence of lung and tail lesions, but the interpretation remains uncertain. The already existing data in the fattening pig sector can be used for the evaluation of animal health and welfare indicators to a large extent. Nonetheless, missing information, differences and changes (over time) in data collection methods introduce biases into the dataset. By improving the data quality and harmonizing collection methods, secondary animal health data could prove to be a useful tool in promoting animal health and welfare.
