Heat stress during transport causes significant suffering and death in livestock, particularly pigs; temperature-controlled vehicles and journey time restrictions in summer reduce impacts.
Livestock transport in high temperatures combines several welfare insults: the inherent stressors of transport including handling, loading, novel environment, and social disruption, with the additional physiological challenge of heat stress. Pigs are especially vulnerable because they cannot sweat effectively and rely on panting, which is impaired when ambient temperatures are high. Mortality events during summer transport receive periodic media attention but represent a fraction of the total welfare burden, which extends to non-lethal heat stress affecting millions of animals. Precautionary transport restrictions during high-temperature conditions, combined with vehicle cooling systems, are the most effective available mitigation.