To be able to measure, document and improve animal welfare, it is crucial to be able to define it. Animal welfare is a complex and multidimensional term. However, several definitions and classifications exist. The five freedoms (freedom from thirst and hunger, freedom from discomfort, freedom from pain, injury and diseases, freedom to express natural behaviour, freedom from fear and distress) were first defined in the UK in 1965 and refined in 1979. Later, an EU project named Welfare Quality® defined animal welfare using four principles (good feeding, good housing, good health and appropriate behaviour) with 12 measurable criteria. Of these, ten are particularly relevant on the day of slaughter, while a 13th criterion can be added – absence of fatigue (Brandt, 2016).
Animal welfare can also be considered at three levels: emotions (Is the animal happy, scared, etc?), biology (Is the animal ill? Does the animal have any injuries? Is it hungry?) and naturalness (access to outdoor areas, playing materials, etc). Research has shown that consumers primarily define animal welfare in terms of naturalness, followed by absence of pain (biology) and happiness (emotions). In contrast, professionals (farmers, veterinarians, scientists) mainly define animal welfare from a biological point of view, followed by emotions.
On the day of slaughter, it is possible to use the pigs’ natural curiosity to make them move from the stable at the farm to the stunner. It is possible to design the truck and the lairage in such a way that the pigs are not frightened, and, by ensuring optimal stunning conditions, any pain suffered by the animals can be minimised. In this way, all three levels of animal welfare can be taken into account when the animals are handled on the day of slaughter.
 Assessment of welfare of finishing pigs from farm to slaughter. Pia Brandt, PhD thesis, Science and Technology, Aarhus University and DMRI.