tOver the last 15 years, rising sow fertility has led to a considerable increase in litter size. Asa consequence, the number of live born piglets may outnumber the number of functionalteats, and surplus piglets are removed from the sow at the age of 3–6 days and fed withartificial milk. The objective of this study was to compare the behaviour of piglets raisedin a commercially available artificial rearing system (group size: seven piglets) with thatof piglets reared by the sow in a loose farrowing pen (seven focal piglets observed perlitter). The behaviour of 98 piglets raised artificially (7 batches) and 82 piglets reared bythe sow (6 batches) was videotaped on days 4, 11 (artificially raised piglets only) and 18after introduction of the piglets to the artificial rearing system. Belly nosing, manipulationof a pen mate, play-fighting, aggressive behaviour and resting were assessed by continuousfocal observation twice a day in the periods from 05:00 to 10:15 and from 13:00 to 18:15.Data were analysed by using linear mixed-effects models.Belly nosing was hardly ever observed in piglets reared by the sow, whereas the durationas well as the frequency of this behaviour increased between days 4 and 18 in piglets raisedartificially. Moreover, artificially raised piglets spent more time manipulating a pen mate,showed less play-fighting, exhibited more aggressive behaviour and had shorter restingbouts compared with piglets reared by the sow. Finally, total duration of resting decreasedfrom day 4 to day 18 in artificially raised piglets and increased in piglets reared by the sow.It is concluded that piglets removed from the sow at an early age and raised artificiallyredirect massaging behaviour to their pen mates, resulting in high levels of belly nosing andindicating impaired animal welfare. Moreover, the small space allowance in the tested artifi-cial rearing system may additionally account for behavioural differences observed betweenartificially raised piglets and piglets reared by the sow in a loose farrowing pen.