Behavioural characteristics of fatal piglet crushing events under outdoor conditions

Abstract

Piglets being crushed by the sow is a major welfare challenge in outdoor pig production. To develop interventions with the highest impact on mitigating crushing, it is necessary to know whether the major behaviour leading up to crushing can be considered mainly sow- or piglet-related or due to inappropriate housing conditions and thus whether the genetics of the sow is a factor of importance. In this observational study, piglets classified as fatally crushed based on necropsy were identified on video recordings. Seventy-two crushing events were observed on video in 32 litters. Forty of the events took place in 17 litters born by DanBred Landrace × Yorkshire hybrid sows while 32 events took place in 15 litters born by Topigs Norsvin TN70 hybrids (TN70). The fatal posture changes were rolling (31%), standing to sternal lying (22%), standing to lateral lying (11%, where half were classified as ‘flopping’), sitting to sternal lying (11%), stepping on a piglet (11%), minor movement (10%), sternal lying to standing (3%) and lateral lying to standing (1%). We hypothesised that a larger proportion of the fatal crushing events could be attributed to either inadequate maternal behaviour (no exploration of piglet location before lying down, ‘flopping’ or not responsive to squeezing a piglet), inappropriate housing (squeezing against inventory), low piglet vitality (weak/damaged before) or an unattractive creep area (piglets clustering near the sow). There were no detectable differences between parity and hybrid on whether the sow explored before or made a posture change after crushing. One-third of the crushed pigs were weak/damaged before and took up a larger proportion of the fatally crushed piglets in DanBred (38%) vs. TN70 (16%) sows. ‘Flopping’ and squeezing against inventory were rare (7% and 1%, respectively). The sow explored before lying down in 42% of the events. Exploring before occurred more often before lying sternal and before stepping on a piglet than for all other fatal sow posture changes (P < 0.01). In 18% of the fatal events, the sow made a new posture change within one minute. Based on the findings, options to reduce crushing are discussed, including genetic selection for maternal behaviour and more robust piglets, housing conditions to slow sow posture changes and/or by attracting piglets away from the danger zone.