Crushing of piglets by the mother sow ( Sus scrofa)—purely accidental or a poor mother?

Abstract

Around 50% of the postnatal death in piglets is caused by crushing or overlying by the domestic sow ( Sus scrofa) when they are kept loose in a farrowing pen. To solve some of these problems, much research attention has been directed towards the farrowing environment. However, previous experiments show that within one farrowing environment there is a large variation in piglet mortality among sows (e.g. [Wechsler, B., Hegglin, D., 1997. Individual differences in the behaviour of sows at the nest-site and the crushing of piglets. Appl. Anim. Behav. Sci. 51, 39–49.]), and recent studies suggest that individual differences in maternal behaviour may explain some of this variation. The aim of the present study was therefore to investigate differences in behavioural characteristics related to maternal abilities between sows that crush several of their piglets and those that do not crush any of their piglets. A sample of 59 healthy, hybrid (Landrace × Yorkshire) sows were video recorded from 2 days before until 4 days after farrowing. From this material, 11 that had not crushed any of their piglets (‘Non-crushers’) within the first 4 days after farrowing and 11 sows that had crushed two or more of their piglets (‘Crushers’) within the same time period, were selected for further behavioural tests and analysis. Sows that did not crush any of their piglets showed a more protective mothering style (i.e. performed more nest building activity, responded sooner on piglet distress calls, initiated nose contacts sooner after presentation of distress calls, nosed more on the piglets during posture change, were more restless when the piglets were taken away) and were socially more flexible (avoided conflicts to a larger extent) in a grouping situation than sows that crushed several piglets. Crushing as a cause of neonatal death in piglets is therefore highly related to mothering style.