Abstract
The possibility to express natural behavior, i.e. the adaptive behaviors resulting from natural selection, is now an accepted dimension of the definition of good animal welfare. Other factors considered are good biological functioning, the limitation of negative affective states, and the experience of positive affective states. Indeed, a mismatch between these behavioral adaptations of farm animals and the environment they are reared in often leads to welfare problems. This concept of animal welfare was formulated 20 years ago by Fraser et al. (1997, Anim. Welfare 6:187–205) and is based on older experiments observing the behavioral needs of farm animals in a more natural environment. The study of the natural behavioral repertoire of farm animals helps to determine which behaviors are strongly motivated. Failure to express such behaviors could lead to negative affective states, such as frustration, and emergence of deviated behaviors, such as stereotypies. Understanding the natural behavioral repertoire also allows the identification of additional behaviors that are expressed more opportunistically (Fraser and Duncan 1998, Anim. Welfare 7:383–396) and are often associated with the experience of positive affective states. When considering the sow and piglets during the lactation period, their natural behaviors have been extensively described in the 1980’s. Although several attempts were made to design housing systems more in line with the behavioral needs of sows and piglets, these were poorly adopted in intensive pig production systems. This presentation will provide a review of the key components of these alternative housing systems, how they answer the behavioral needs of sows and piglets and how they can be beneficial to their welfare, but also, to the farmer.