Deck height did not affect behavioural measures of ‘natural movements’ and ‘adequate ventilation’ during 8 h and 23 h transport of weaner pigs

Annually, more than 30 million weaner pigs cross borders between EU member states mainly transported for further production. The current EU regulation states that the internal deck height of the transport vehicles must on no account hinder natural movements and provide adequate ventilation but without including specific norms. The aim of the present study was to examine impact of deck height (60 vs 80 cm and 70 vs 90 cm) on behaviour reflecting natural movements and adequate ventilation during 16 short (8 h) and 16 long (23 h) journeys of 20-25 kg pigs, mimicking commercial conditions. A secondary aim was to describe the behaviour progressed from departure to arrival including the driver break during short journeys. To address the aim, the first task was to select appropriate behavioural measures that could robustly be annotated with the limited vertical space. As a consequence, head butting against the ceiling and drinking behaviour were omitted in pilot observations. The final behaviours were body posture including huddling and huddling location analysed using 15-min interval instantaneous scan sampling. The frequency of aggression and a pig standing on another pig was recorded using continuous sampling during selected 20 min recording sessions (in total 160 and 120 min for short and long journeys, respectively). During short journeys, this included recording sessions placed immediately before, during and after the mandatory break of the livestock driver. Mixed effects models were used to analyse effects of deck height and the following co-variates: hour since departure, microclimatic conditions and vehicle speed. No effect of deck height was found on any of the selected behavioural measures. When examining behaviour of the pigs before, during and after the break, no differences in lying behaviour were found, but for one of the vehicle elements, the trailer, an increase in aggressive behaviour was observed during the break. Overall, the results showed a complex pattern of relations affecting the behaviour of the pigs, such as the microclimatic conditions and driving speed interacting with hour since departure. These findings varied to some extent depending on vehicle element (lorry or trailer) and journey duration (8 h or 23 h, with the associated different stocking densities). Taken together, the results showed that increasing the deck height did not lead to detectable changes in the behaviour of the weaner pigs, but that many other factors influenced the behaviour of weaners during transport and may thus also influence their welfare. • Deck height did not affect lying behaviour, aggression and pigs 'overlapping’ • 88.9% were lying per hour on long journeys and 51.5% on short journeys • Lying was unaffected by driver breaks; aggression showed inconsistent effects • Surprisingly, higher in-vehicle temperature was associated with less lying pigs • Higher speed correlated with more lying and less aggression