The Swiss Federal Act on Animal Protection (1978) requires the sale of mass-produced housing systems for farm animals to be authorized by the Federal Veterinary Office. Authorization is only granted for housing systems that safeguard the animals' welfare. A concept for the assessment of Animal Welfare has to provide a high forensic value. The capacity of farm animals to adapt to an intensive housing system can be directly examined, whereas the existence and extent of subjective feelings can only be assumed. In our concept the examination focuses on the interaction of individuals with their artificial environment. The main question is whether or not the individuals are able to cope with given nonspecific (e.g. temperature, humidity) and specific (e.g. drinking troughs, behaviour of conspecifics) stimuli in order to reach the immediate (e.g. drinking, make way for) and ultimate (survival, reproduction success) goals. Animals of the same breed are observed in a highly diverse environment in order to determine normal behaviour. Whether behavioural expressions which differ significantly from normal behaviour are adaptive to the restrictive housing conditions is judged by the behaviours' consequences for both, the individuals and the environment. Many studies prove the concept's high forensic value and the authorities prefer conclusions based on this concept to others referring to the animals' motivational and emotional state. However more research has to be done with respect to animal welfare in farm and laboratory animal breeding as well as in the use of laboratory animals for experimental studies.