Pigs possess a poor temperature regulation system. They warm one another by forming piles . Due to breeding for high volumes of meat and quick growth, the pig s circulatory system has not sufficiently kept up. Animals with pneumonia and pericarditis who have gotten ill while being fattened are particularly sensitive. They suffer breathing difficulties and oxygen deficiencies even at relatively low stress levels, and usually die first.
Pigs are omnivores with a one-chamber stomach.
If the stomach is filled during transport, much blood is required for digestion. The circulatory system is then less capable of handling stress, and death during transport occurs frequently. One also speaks of the travel sickness among pigs.