Choosing to take it cool: a pilot study on changes in gestating sows laying area preference when given access to resting areas with floor-cooling during summer heat.

Heat stress is an increasing concern in pig production as ambient temperatures rise due to climate change. Pigs have limited physiological capacity to dissipate heat and rely largely on behavioural strategies to regulate body temperature. Floor cooling has therefore gained interest as a potential method to alleviate heat stress, particularly since pigs spend large proportions of time lying down. The aim of this pilot study was to investigate whether underfloor cooling influenced lying area preference of gestating sows during warm summer conditions. The study was conducted at the Swedish Livestock Research Centre, Lövsta, Uppsala, Sweden, during July 2025. A group pen (160 m²) housing 31 gestating sows included three concrete resting subsections (A-C) with a total area of 27 m². Underfloor cooling infrastructure had been installed in the concrete slab using embedded plastic tubing. During the experimental period, cold water circulation was applied in subsection A (17 °C) and subsection B (12 °C), while subsection C served as an uncooled control. Sow occupancy of the resting areas was recorded by video during 72 h before cooling commenced and during 72 h with cooling in operation (after a 72 h adjustment period). Still images taken at 30-min intervals were used to calculate occupancy (sows/m²). Data were analysed using mixed linear models. Before cooling, average occupancy did not differ between areas (0.24, 0.22 and 0.26 sows/m² in subsections A, B and C respectively). When underfloor cooling was applied, occupancy increased markedly in the cooled areas (0.44 and 0.41 sows/m² in A and B) compared with the uncooled control (0.27 sows/m²) (P < 0.001). Outdoor temperature significantly influenced occupancy in subsection A and B during the cooling period (P < 0.001), with higher densities observed at higher temperatures. These results indicate that gestating sows preferentially used cooled resting areas when average outdoor temperatures exceeded 20 °C, hence changing their preference for where to rest. Although based on a short pilot study in a single group pen, the findings indicate that underfloor cooling may be a promising strategy to alleviate heat stress however further studies are needed to examine the benefits and the motivations for the sow's changes in preference of resting area.