Transporting farm animals in hot weather creates serious heat stress risks, with confined, poorly ventilated vehicles in summer causing suffering and death that is preventable with proper planning.
Heat stress during transport causes acute suffering - animals experience panting, hyperthermia, cardiovascular stress and in severe cases death from heat stroke. This is a welfare problem that is most acute for poultry (whose temperature regulation is limited in crates) and pigs (who cannot pant effectively and have no sweat glands). Welfare improvement requires scheduling transport in cooler parts of the day, enforcing vehicle ventilation standards, reducing journey times, and providing effective temperature monitoring inside vehicles. Some countries now have absolute temperature limits above which transport of certain species is prohibited.