Significance of Physiological Criteria in Assessing Animal Welfare

Abstract

Many people believe that well-being and suffering are amenable to physiological studies. Evidence is presented to support the idea that when used in conjunction with behavioural data, physiological variables allow predictions about the ways the animals react to their environment. When measured in animals acutely exposed to aversive situations, physiological criteria are reflecting more the intensity of the emotion experienced than its qualitative aspect. On a long-term basis, however, hormonal activities are differentially reflecting the different perceptions of the animal. The range of presently available physiological indicators can be increased by studying neurochemical changes in the brain or by searching for alterations at the level of effector organs (e.g. lymphocytes and immune function). In either case, the basic issue is the relevance of such indicators for animal welfare. Since the use of physiological indicators can only allow to assess the constraints exerted by the environment on the physical and mental integrity of the organism, there is a need to define the maximal constraints which are believed to be acceptable.