The domestic pig shows all the behaviour patterns of the wild boar when observed in semi-natural conditions. Thus, intensive commercial pig production systems are very likely to cause stress and affect welfare.
Different housing systems are used for pig production but the welfare of pigs varies between the systems. Recent pig production systems based on the natural behaviour of pigs have been able to combine high production figures with good animal welfare.
The welfare of an animal is "its state as regards its attempts to cope with its environment" (Broom, 1986). In this definition, welfare includes "pleasant and unpleasant mental states of the animal" (Duncan, 1996).
Good animal welfare is certainly not limited to "natural" environments and there are many ways in which what happens to animals in the wild leads to poor welfare. While the semi-natural conditions may give indicators as to what is important for animals, welfare of the animal in a given situation depends on the housing system and the coping ability of that animal.