Sow mortality in Danish herds – Differences between production systems, annual and seasonal trends and association to herd sizes

Housing and management are likely to play a role in sow mortality. Therefore, it is of interest to scrutinize differences in mortality rates between systems that are markedly different on these parameters. In this study, we used Danish national databases to extract data from all organic and conventional sow herds in the period 2015-22 to model mortality rates in conventional and organic systems. Furthermore, we used temperature data to investigate potential associations between summer season and temperatures on sow mortality in each of the two systems. Finally, for the conventional system we investigated potential associations with herd size. In both systems we saw a marked variability in mortality rates between herds. During the first four years of the study period mortality rates in the two systems were similar - approximately 10 % of sows died per year. From 2018 and onwards, mortality rates in conventional herds increased and reached an average of 14.4 % in 2022. In this system, we found a positive correlation between herd size and sow mortality. In organic herds, the mortality rate stayed at 10 % throughout the study period. In both systems, mortality rates were higher in the summer months, but only in the organic system the increase seemed to be associated with high temperatures. Our results indicate that sow mortality is associated with management and housing factors. They confirm that sow mortality is slightly higher in the summer months but point out that other factors than high temperatures seem to impact the sow mortality, especially in conventional herds.