Thermal variability across truck decks and at off-truck rest periods influences rumen temperature in transported Bos indicus cattle

Assessing cattle responses to commercial long-distance road transport is challenging. Physiological effects of environmental conditions and long-distance transport on rangeland-sourced beef cattle in Western Australia (WA) were examined. The rumen temperature of 131 Bos indicus cows (≥343.0 kg, condition score >2.5) and environmental ambient wet bulb temperature (WBT) were recorded across the journey of seven trials. Each four-day trial consisted of cattle being transported through varying climatic zones in WA over a 2,427 km multi-stage journey consisting of regulated rest stops, vehicle reconfiguration, and overnight off-truck rest prior to slaughter. Rumen temperature monitoring revealed pronounced temperature decreases during the off-truck period, reaching as low as 35.8 °C, presumed to indicate water intake at the Depot yards. The WBT varied substantially throughout the journey, with daytime peaks of 21.2˚C and night-time lows below freezing. Notably, trends in WBT differences between truck decks suggested location on the truck may contribute to variable thermal conditions for cattle. More than half of the animals were pregnant, emphasizing the need for further welfare considerations. Adjusted rumen temperature (T AR ) modelling confirmed a significant 0.82 °C (95% CI: -1.12 to -0.53; p < 0.001) decrease during off-truck rest compared to when cattle were at Holding Yards prior to transport. While WBT generally had limited direct association with rumen temperature, a significant effect was noted when cattle were offloaded into the Depot Yards, with cattle experiencing a 0.03 °C increase in T AR per 1 °C increase in WBT (95% CI: 0.01 to 0.06; p = 0.005) compared to when cattle were at the Holding Yards prior to the start of the journey. The findings highlight the complex relationship between environmental conditions, transport logistics, and animal physiology, and reinforces to industry the value of incorporating structured off-truck rest, improved truck design, and broader welfare indicators into transport management strategies.