Effects of season on the behaviour of early-weaned piglets during and immediately following transport

In North America commercial transport of piglets occurs without supplemental heat, over long durations (24 h) and without feed and water. Scan sampling was used to compare behaviour across seasons (summer, fall, winter) and over representative durations (Control, 6, 12 or 24 h) to help assess welfare. Six groups of 48 Cotswold piglets (17 ± 1 d) were weaned and transported along highways in a van equipped for video and temperature recording. Following transport, piglets were studied in groups of four, in weanling pens with free choice feed and water. Resting during transport increased in frequency from 59.8% (1–12 h) to 91.5% (13–24 h). This pattern was more defined in winter and fall implicating cold as a causal factor. Fatigue, as observed in slaughter hogs, may also be a factor. Higher levels of post-transport resting in transported (81.4%) compared to control piglets (77.5%) supported this interpretation. Habituation to transport conditions may also have affected behaviour as piglet interactions commonly associated with dominance hierarchy establishment, were more frequent, and sitting, a behaviour associated with stress post-weaning decreased in the last 12 h of transport. As the duration of transport increased, post-transport drinking frequency increased, although significance was reached between control (2.4%) and 24 h of transport (3.7%) only. Long transport durations may thus delay hierarchy development, require additional coping strategies with respect to cold and increase the risk for dehydration. However, indications for habituation to some aspects of transport after 12 h are also apparent. During winter transport the frequency of piglet interactions (three piglets) was much lower than in summer (39 piglets) and fall (18 piglets) indicating that the cold temperatures may have affected establishment of a dominance hierarchy. Summer and winter transport differed from fall transport, with less resting (5.5% versus 9.2%) and standing (5.5% versus 9.25%), and more sitting (0.52% versus 0.28%) during the fall, a pattern consistent with increased stress during fall transport. Higher levels of resting for 3 days in winter and 2 days in summer could indicate more post-transport fatigue in these seasons. Transport, irrespective of season, resulted in behaviour indicative of coping strategies. It is important to determine which stressors have the greatest impact in each season and develop strategies to reduce the effects of transport on welfare.