Risk Factors Associated with Sow Mortality Under the Condition Of a Production System in the Midwestern United States During 2019-2021

Breeding herd mortality has significantly increased in different countries in the past years and it has been a growing concern to the global swine industry. Sow mortality increases economic losses, including increases in replacement rates and opportunity costs, as well as negatively affecting employees’ morale. The aim of this study was to assess herd-level risk factors associated with sow mortality in a large swine production system located in the Midwestern United States. This retrospective observational study used available production, health, nutritional, and management information between July 2019 and December 2021. A Poisson mixed regression model was used to identify the risk factors and built a multivariate model, with the outcome being the weekly mortality rate per 1,000 sows. The main reported reasons for sow mortality in this study were sudden deaths (31.22%), lameness (28.78%), prolapses (28.02%), and other causes (11.99%), respectively. Breed-to-wean herds classified as porcine reproductive and respiratory syndrome virus (PRRSV)-epidemic status, PRRSV-epidemic and Mycoplasma hyopneumoniae (Mhyo)-positive herds, PRRSV-epidemic with no feed medication added, open pen gestation farms, and Senecavirus A (SVA)-positive herds were associated with higher sow mortality rate. The interaction between the PRRSV-epidemic and Mhyo-positive herds, PRRSV-epidemic and fall season, and non-medicated feed were also significantly associated with a higher weekly sow mortality rate. This study identified and measured the major risk factors associated with sow mortality rate in breeding herds under field conditions.