Can body nosing in artificially reared piglets be reduced by sucking and massaging dummies?

Selection for hyper-prolific sows has substantially increased litter size. Consequently, the number of piglets in a litter may exceed the number of functional teats. To solve this problem, surplus piglets may be removed from the sow 2 days after birth and raised artificially. However, these piglets show increased levels of oral behaviours, such as belly nosing, directed at other piglets. This behaviour resembles massaging and sucking at the sow's udder and thus is considered to be redirected suckling behaviour. The present study investigated whether oral behaviour directed at piglets can be reduced in artificially reared piglets by providing them with sucking and massaging dummies. In a two-by-two between-group factorial design, the artificial rearing pens were equipped with one of four treatments: a sucking dummy, a massaging dummy, a combined sucking-massaging dummy, or no dummy. The behaviour of 126 piglets (in 21 groups of 6 piglets) was scored from video by continuous focal observation lasting 90 min per piglet each on days 4 and 18 after introduction to the artificial rearing system. Data were analysed using linear mixed-effects models. Body nosing (composed of belly nosing and nosing on any other body part) increased from day 4 to 18 in all treatments, but piglets provided with a combined sucking-massaging dummy showed the smallest increase. Piglets spent more time nosing the combined dummy than the sucking or the massaging dummy. However, there was no causal inverse relationship between the duration of body nosing and dummy nosing. All but one piglet showed body nosing at least once. Resting, play-fighting, or oral manipulation of piglets (other than body nosing), dummies, and pen equipment were hardly affected by the treatments. Piglets with a combined dummy tended to have a longer average resting bout duration compared with piglets in other treatments. In conclusion, only the combined sucking-massaging dummy was effective in reducing the increase in body nosing over time. However, this reduction was rather small in absolute terms and the combined dummy did not prevent body nosing. The tested dummies were thus not successful in eliminating the redirected oral behaviour in artificially reared piglets.