Heat stress during transport is a leading cause of animal welfare emergencies and mortality in livestock, with high ambient temperatures, poor ventilation, and long journey times the primary risk factors.
Transport heat stress causes a cascade of physiological responses — elevated heart rate, panting, drooling, and in severe cases, collapse and death from heat exhaustion. Pigs are especially vulnerable because they cannot sweat and rely entirely on panting to dissipate body heat. In poorly ventilated vehicles during summer loading, temperatures inside livestock compartments can exceed 40 degrees Celsius even when ambient temperatures are moderate. Dark-colored vehicles absorb more solar radiation than white ones. The welfare harm of heat stress is progressive — animals may survive transport but arrive with compromised immune systems and elevated cortisol that affects health for days afterward.