LAUSR

Abstract The hut temperature in outdoor pig production during summer can exceed the upper critical temperature of lactating sows. Therefore, sows may experience hyperthermia, a condition which has several adverse consequences for the welfare of both sow and piglets. Thus, the aim of the current study was to investigate possible benefits of providing sows with access to an alternative shaded area, apart from the huts, constituted by an area with poplar trees within the farrowing paddock. The study consisted of two parts: Part one was an experimental study investigating the effects of providing sows with access to poplars. Fourteen sows with access to poplars and 14 sows without access to poplars were included. In the second part of the study, including 57 sows, the sows’ use of the poplars was studied. In both study parts, sows were studied during four periods: pre-partum (day 2 pre-partum until, and including, the day of farrowing (day 0), early postpartum (day 1 to 4 postpartum), late postpartum (day 5 to 7 postpartum) and late lactation (two observation days, 13 and 28 days after expected farrowing, range day 11 to 31 postpartum). Access to poplars affected the sows’ use of the farrowing hut, and an interaction was found between temperature and treatment (access to poplars or no access) so that access to poplars resulted in a decreased use of the hut at higher hut temperatures. No effect of temperature was seen for controls. Maximum surface temperature of sows was only affected by hut temperature and increased with increasing temperature, whereas wallowing was affected by parity group and period. The odds of wallowing were higher for parity group 1 and pre-partum. Whether the sows chose to enter the poplar area was unaffected by hut temperature but higher pre-partum and in late lactation compared to early and late postpartum. Once inside the poplars, sows lay more when hut temperature increased. Sow location had a major impact on the location of the piglets after removal of the fender, and the piglets followed the sow into the hut and the poplar tree area. In conclusion, sows lay more in the poplar area when hut temperature increased, but the sows total use of the poplars was unaffected by temperature, suggesting, poplars in the farrowing field may serve several purposes this could be as an area for thermoregulation, exploration and foraging.