Leman: Sudden death in sows
Sudden sow mortality is concentrated in early parities and during the peripartum window
14 July 2026
2 minute read
By: [Excerpts of a presentation by Laura Solis and colleagues at Iowa State University, and Iowa Select Farms, USA, during the 2025 Leman Swine Conference]
Sow mortality presents significant welfare and economic challenges in commercial swine production. While parity and physiological stage are recognized risk factors, their interaction with timing and pathology remains poorly understood. Sudden death is a leading cause of sow removal, often surpassing reproductive failure or lameness. Yet its etiology frequently goes undocumented due to limited necropsy implementation. Previous studies have identified gastrointestinal torsions, gastric ulceration, heart failure, and retained piglets, particularly during the peripartum period, the most vulnerable window for sow mortality.
This retrospective study analyzed 150 sudden death cases from two commercial sow farms using systematic on-farm necropsy protocols. Cases were categorized by parity, production stage (breeding, gestation, pre-farrow, farrowed), and death cause. Additional variables included stomach ulcer grade (0– 3), gestation day at death, postpartum interval, and age at first service.
The farrowed period (including farrowing and lactation) accounted for the highest proportion of deaths (56.8%), followed by gestation (days 1–109; 28.1%), pre-farrow (days 110–115; 7.9%), and breeding (open gilts, opportunity sows, and culls; 7.2%). Within the farrowed group, 76% of deaths occurred during the first 7 days postpartum. Among gestating sows, 59% occurred between days 57 and 109, with a peak from days 81 to 109.
Retained piglets were the most common cause of death (29.5%), followed by gastric disorders (including perforated ulcers, acute ulcers, and gastric torsions; 18%), cardiovascular failure (10.8%), and splenic disorders (ruptures and torsions; 9.4%).
Parity 1 and 2 sows represented 49.5% of all deaths. Among parity 1 sows, the average age at first service (AFS) was 264 days (range: 238–313), highlighting variability in gilt development or breeding decisions. Delayed AFS is linked to increased reproductive failure and early removal, while targeting 220–240 days improves gilt maturity, longevity, and lifetime output. AFS is increasingly recognized as a key early-life predictor of sow resilience.
The average gestation length among farrowed sows was 117.5 days. Inducing parturition before a herd’s typical gestation length can result in incomplete farrowing, stillbirths, and poor uterine clearance. Among retained piglet cases, sows had an average of 4.8 fetuses left in the uterus (range: 1–17).
These findings underscore the need for herd- and parity-specific induction strategies to reduce fetal retention and associated mortality. When causes of death were stratified by parity, retained piglets remained the top cause across nearly all groups. Parity 1 showed the most death cause diversity, while older parities (P9–P12) had fewer, more consistent patterns. Nearly two-thirds of necropsied sows had grade 2 or 3 ulcer lesions. Chronic or intermittent stress increases ulcer risk, reinforcing the value of stress-reducing strategies, particularly during late gestation and the peripartum period, to improve sow survivability.
Sudden sow mortality is concentrated in early parities and during the peripartum window, the most vulnerable period for losses. These findings underscore the need for targeted management strategies based on parity, timing, and pathology. Systematic necropsy remains essential to identify preventable causes and guide herd-level interventions.
