Oostindjer, M., van den Brand, H., Kemp, B. et al. 2011. Effects of environmental enrichment and loose housing of lactating sows on piglet behaviour before and after weaning. Applied Animal Behaviour Science 134(1-2), 31-41 .

Weaning of piglets in commercial husbandry systems is earlier and more abrupt than would happen under natural conditions, resulting in low feed intakes and health and welfare problems in the immediate postweaning period. Piglets in commercial systems generally have limited opportunities to learn how to behave and eat like a pig. Interacting more with the sow, as well as providing enrichment, may stimulate the development of social and foraging related behaviours, and make piglets better able to adapt to the postweaning situation. Piglets were housed in a barren or enriched pen with a confined or loose-housed sow preweaning, and at weaning at d 29 were relocated to a barren or enriched pen postweaning (2 x 2 x 2 factorial arrangement, eight treatments, eight pens per treatments, four pigs per pen). Enrichment consisted of increased space allowance, straw, wood shavings, peat and branches. Behaviour was recorded on 4 days pre-(weekly) and postweaning (d 1, 5, 9 and 12).The development of social behaviours and foraging related behaviours was positively affected by enrichment of the lactation pen, but less by sow housing. Postweaning behaviour was most strongly affected by postweaning enrichment, with enriched housed piglets showing higher levels of exploratory behaviours (27% versus 10% of observations), lower levels of belly nosing (0.1% versus 1.0%) and manipulative behaviours (0.2% versus 1.5%), but also less time spent eating (8% versus 9%) than piglets in barren postweaning pens. Piglets from loose-housed sows showed lower levels of belly nosing (0.3% versus 0.7%) and manipulative behaviour (0.8% versus 0.9%), as well as more chewing (6.1% versus 5.5%), food exploration (1.0% versus 0.8%) and play behaviour (0.9% versus 0.7%) postweaning than piglets from confined sows. Enrichment of the lactation pen in itself had few effects on postweaning behaviour, but interacted strongly with postweaning enrichment and sow housing, with piglets from a loose-housed sow switching from a barren to enriched environment showing high levels of play behaviour while piglets from a confined sow switching from an enriched to a barren environment showed high levels of belly nosing and low levels of play (barren-loose-enriched: 1.8% of observations, enriched-confined-barren: 0.1% of observations). Enrichment pre- and postweaning, as well as providing more possibilities to interact with the sow, can thus positively affect how piglet behaviour develops before weaning and how they adapt after weaning. It is important to realize that the preweaning environment, including sow housing, affects how piglets value their postweaning environment and may thus greatly affect piglet welfare around weaning.