Longitudinal field study to assess sow level risk factors associated with stillborn piglets.

The aim of this study was to identify risk factors for stillborn piglets at sow level in commercial pig herds in northern Belgium. In total, 545 sows of 22 pig herds were included in the study. Stillborn piglets were observed in 48.3% of the litters and the mean stillbirth rate of the sows was 7.5%. Two multilevel logistic regression models were used to investigate the risk factors for stillborn piglets. One included the stillbirth occurrence at previous farrowing, while the other one did not. In both models, sows with lower back fat levels (<16mm) at parturition had an increased risk for stillbirth compared to sows with medium back fat levels (16-23mm). Vaginal palpation during farrowing was associated with stillborn occurrence as well. Sows that farrowed during the day were more likely to have stillborn piglets than sows farrowing overnight and each unit increase in total litter size significantly increased the risk for stillborn piglets. Parity was significantly associated with the risk for stillborn piglets when stillbirth occurrence at previous farrowing was taken into account. The risk for stillbirth was 2.5-times higher among sows with >1 stillborn piglets at the previous farrowing compared to sows without stillbirth in the previous parity. In conclusion, high parity sows, large litters, sows with low back fat levels and sows with >1 stillborn piglets at previous farrowing require special attention due to an increased risk for stillbirths. Finally, all practices performed in the farrowing unit should be conducted carefully and without disturbance of the sows during the parturition process.