Herd-, sow-, parity- and service-level risk factors for sow mortality at different reproductive stages: an analysis of production data

Abstract

Abstract Background Sow mortality has been increasing in recent years, posing significant challenges to commercial pig production. High mortality affects animal welfare, farm productivity, and causes substantial economic losses. While previous studies have identified risk factors such as high parity, seasonal effects, and farrowing-related complications, limited research has quantified mortality risk at different reproductive stages in Spain. This study aims to analyze sow mortality patterns and identify associated risk factors. Results Analysis of production records from 16 Spanish farms revealed that 55.59% of sow deaths occurred before farrowing, while 44.41% occurred after farrowing. Mortality risk peaked during late gestation (105–118 days) and again during the first and after the fourth weeks post-farrowing. Several risk factors were identified at farm and individual levels. Internal gilt replacement was associated with increased mortality risk. Before farrowing, sows with parity ≥ 3 and single-service sows exhibited higher mortality. After farrowing, increased mortality was observed in parity 1 sows and those with repeat breeding. Seasonal effects showed highest mortality rates in sows bred in spring and farrowing in summer. Matched case-control analysis revealed that parity 0 sows had a younger age at first service, and deceased sows had shorter gestational length, fewer piglets born, born alive, and a higher incidence of stillbirth fetuses at their last litter before their death. Comparing their lifetime performance, dead sows had younger gilt age at first service, fewer parity at removal, higher average number of piglets born, born alive, born still and born mummified per parity, but they had fewer weaned piglets and nonproductive days. Conclusions This study identifies late gestation and the first week postpartum as critical windows for sow mortality risk. Internal gilt replacement and parity extremes emerged as key herd- and sow-level risk factors, while mortality was also higher among sows farrowing in summer. Repeat breeding prior to farrowing was associated with lower mortality. These findings support integrating reproductive history and herd-level replacement strategy into sow management and culling decisions.