Sow mortality in a pig production system in the midwestern USA: Reasons for removal and factors associated with increased mortality.

Background: Sow mortality has become a growing concern in the pig production industry over the past decade. Therefore, we aimed to describe sow mortality and associated factors in a production system in the midwestern USA.

Methods: Mortality records from 2009 to 2018 for four farrow-to-wean farms were described. Environmental, farm- and individual-level factors associated with weekly mortality and individual risk of dying throughout a sow's lifetime were assessed.

Results: Deaths occurred at a median of 116 days from last service, or 26 days postpartum. The median parity upon death was two. Overall, the main reasons for death were locomotion (27%) and reproduction (24%). A higher weekly number of deaths was associated with spring (incidence rate ratio [IRR] 1.27, compared to winter). Sows had a higher mortality when they were exposed to at least one porcine reproductive and respiratory syndrome (PRRS) outbreak during their lifetime (IRR 1.55) and when housed in groups (pens) during gestation (IRR 1.32). Conversely, they had  a lower mortality when housed in filtered farms (IRR 0.76), accounting for an interaction term between parity at removal and PRRS outbreak exposure.

Limitations: Issues with data completion and information accuracy were present, and prospective data collection throughout sows' lifetimes is still needed.

Conclusion: Efforts to reduce infectious diseases within the herd and manage environmental stressors should help reduce mortality.