Overall animal welfare assessment reviewed. Part 1: Is it possible?

Several authors have concluded that scientists should not attempt to perfor m overall animal welfare assessment (OWA). They argue that scientists have continued to fail to make progress in this area and that value judgements a re inherently involved in OWA for which science cannot provide answers. We take a more positive attitude toward OWA and argue that scientists should a void creating a self-fulfilling prophecy. OWA is necessary for making actua l moral and political decisions. Science has already accumulated much relev ant information about welfare and this information should be applied in dec ision making. The task of OWA is to assess welfare based on knowledge of the biological n eeds of animals. Weighting of welfare relevant factors constitutes a proble m. However, when scientists cannot provide empirical data to solve weightin g issues, this does not mean that rational answers cannot be found, e.g. in the form of procedural rules. OWA is conceived as a problem of multi-crite ria decision making with fuzzy information. It focuses on the descriptive a spect of welfare, i.e. on what the welfare status of the animals really is without taking an ethical stance. The welfare status of animals depends on their biology and on the way animals assess their own welfare. It does not depend on how it happens to be perceived by us. Even though OWA necessarily remains a human activity, it is not arbitrary, nor does it allow of multip le 'correct' answers. OWA is a descriptive activity that can achieve more a nd more accuracy as science proceeds.