Behaviour of fattening pigs in a rearing system with an outdoor courtyard The evolution of pig farming systems towards better consideration of animal welfare often implies that the animals have access to an outdoor courtyard or run. A study was conducted to measure, in such a system, the feeding activity and use of the indoor and outdoor housing areas by fattening pigs. The tested device included an indoor area on sawdust bedding (1.1 m²/pig) and a covered outdoor area on a concrete floor (1.3 m²/pig). Three batches of 10 pigs from two breeds (two Large-White and one Basque) were reared in this device, in two successive replicates. The animals were equipped individually with an RFID chip, and antenna devices made it possible to determine their location (outside, inside, at the trough). On average over the entire fattening period, the animals spent 1.8 h/d outside, with high variability among animals (0.9-3.3 h/d, P < 0.001). The time spent outdoors depended greatly on the time of day (P < 0.001). At night, pigs spent a short proportion of time outside (3%, on average). From 7 a.m., the time spent outdoors each hour increased, peaking at 18 % around 2 p.m., and then decreased steadily until 12 p.m. The time spent outdoors also depended greatly on outdoor temperature (P < 0.001). Pigs spent nearly all of their time inside when the temperature was below 7°C but about 25% of their time outside when it was above 19°C.