Hötzel, M. J., Pinheiro Machadon F., L. C., Wolf, F. M. et al. 2004. Behaviour of sows and piglets reared in intensive outdoor or indoor systems. Applied Animal Behaviour Science 86(1-2), 27-39.

In this study, we compared the behaviour of sows and piglets, as well as the mother–offspring interactions of sows and piglets during lactation, and the post-weaning behaviour of piglets reared in the outdoors or in confinement throughout the whole production period. An experiment was carried out at the outdoor and indoor units of the experimental station of EMBRAPA-CNPSA, south Brazil. The behaviour of sows (n=8 per treatment) from delivery to weaning (at 21 days) and their litters (n=5–8 per treatment) from birth to 50 days was recorded for 7 h per day on seven occasions, at the approximate age of 1, 12, 20, 21, 35 and 50 days. Results were transformed to relative frequency and analysed by ANOVA. In contrast to sows confined in crates, which spent 100% of the time in close contact with the litter, the time outdoor sows were inside the hut decreased from 86% on day 1 to less than 30% on days 12 and 19 after delivery. Outdoor sows spent more time standing (P<0.02) walking (P<0.04) and exploring the environment (P<0.04) than confined sows, which spent more time sitting (P<0.01). During lactation confined piglets spent more time interacting with their mothers (P<0.01), nursing (i.e. suckling, massaging udder and fighting for teats: P<0.01), belly-nosing (P<0.01) and displaying other oral–nasal and agonistic behaviours directed to penmates than outdoor piglets (P<0.05), while outdoor piglets spent more time feeding and exploring the environment (P<0.05). At and after weaning confined piglets spent more time belly-nosing (P<0.05) and displaying agonistic (P<0.01) and oral–nasal behaviours directed to penmates (P<0.05) than outdoor piglets. We conclude that the rearing systems studied cause significant differences in the behaviour of both sows and piglets during lactation, as well as in the social interactions between the sows and their litters and the subsequent behaviour of piglets after weaning.