Evidence on welfare during the transport journey to slaughter
Transport to slaughter is a concentrated welfare risk for pigs. Loading, vehicle movement, mixing with unfamiliar pigs, temperature extremes, limited food and water, and unloading at slaughter plants cause significant acute stress and, in a proportion of animals, death. Transport mortality is an economically visible indicator of welfare failure that has driven industry improvement in some sectors, but welfare harms well below the mortality threshold remain prevalent and underaddressed.
Loading: Unfamiliar handlers, narrow ramps, electric prod overuse, and mixing of unfamiliar pigs at loading cause acute stress. Loading injury rates of 1-5% are common in poorly managed operations.
Mixing: Pigs establish dominance hierarchies through fighting; mixing pigs from different pens during loading causes fighting, injury, and chronic stress. Pre-transport mixing at farm is preferable to vehicle mixing.
Heat stress: Market-weight pigs are highly heat-susceptible; summer transport above 23°C with inadequate ventilation causes heat stroke and death. Heat-related transport mortality is entirely preventable.
Journey duration: Physiological stress indicators remain elevated throughout journey; longer journeys cause greater cumulative welfare harm.
Evidence-based improvements include: trained loaders using low-stress handling; reduced stocking density in transport vehicles; ventilated vehicles with continuous monitoring; journey time limits proportional to animal weight; appropriate lairage conditions with water access. The PRRS (Positive Results from Reduced Stress) program data shows that reducing transport stress reduces pork quality defects (PSE pork) simultaneously with improving welfare.