The assessment of animal welfare
Paul H. Hemsworth
Animal Welfare Science Centre, The Melbourne School of Land and Environment, The
University of Melbourne, and the Department of Primary Industries (Victoria), Parkville,
Victoria 3010, Australia.
In an ethical analysis of an animal use, science can provide the factual basis of
understanding the impact of a husbandry or housing practice on the animal, particularly its
impact on the welfare of the animal. However, there is considerable uncertainty within
science on the concept of animal welfare.
Although there is a wide acceptance of the scientific method in problem solving, its
ability to contribute to the welfare debate has been limited to some extent by a lack of
consensus on the scientific approach to studying animal welfare. For many scientists, animal
welfare is defined and measured on the basis of how well the animal is performing from a
biological functioning perspective. For others, animal welfare concerns affective states, such
as suffering, pain, and other feelings or emotions, and thus animal welfare can be studied by
measuring animal preference on the basis that preferences are influenced by the animal’s
emotions, which have evolved to motivate behaviour in order to avoid harm and facilitate
survival, growth, and reproduction. One concept in the literature, albeit not well enunciated,
is predicated on the view that the welfare of animals is improved in environments or
situations in which the animals display normal or “natural” behaviour. These different
concepts or views on animal welfare lead to the different methodologies to assess an
animal’s welfare.
This scientific uncertainty does not necessarily diminish the robustness of the
research utilising methodologies or measurements arising from these views or concepts, but
it does raise the question of the relatedness of these concepts. In other words, is biological
dysfunction associated with, or does it lead to, negative affective states and vice versa? In a
similar context, is an inability to perform normal or ‘natural’ behaviours associated with
biological dysfunction and/or negative affective states? Therefore, are the resultant
methodologies measuring the same adverse physiological and mental state(s) in the animal?
There are several commonalities in the rationale for these approaches. For example,
it is considered that animals, at least in the wild, will be motivated to choose those resources
or behaviours that maintain homeostasis or biological functioning to optimize their fitness;
that is, optimize their growth, reproduction, injury status, health, and survival. Furthermore,
feelings or subjective affective states have evolved to motivate behaviour to meet needs that
have to be satisfied in order for the organism to grow and reproduce normally and to remain
healthy and survive. The functional approach to welfare assessment includes both
behavioural and physiological indicators of poor coping, as well as fitness variables such as
growth, reproduction, injury and health. This conceptual convergence suggests a way
forward in developing a broader consensus on the study of animal welfare by reducing both
conceptual differences and consequently methodological differences in animal welfare
science. The validity of the welfare criteria can be tested in several ways: first, with the
finding that there are correlations between independent measures of different concepts of
animal welfare; and second, with the finding that an intuitively aversive condition reduces
animal welfare on the basis of the measures of different concepts of animal welfare.
Therefore, the basis of the methodology used by scientists to assess animal welfare
should routinely be provided so that individuals using science in their decision-making
appreciate both the rationale for the methodology and its limitations. Research utilising wellaccepted stress models is required to understand the relationships between these concepts
and methodologies, with the overall objective of developing a broader consensus on animal
welfare methodologies to reduce the methodological and interpretative differences in animal
welfare science. In the meantime, the approaches or methodologies that arise from the
welfare concepts of normal biological functioning and affective states should guide current
welfare research methodology. Indeed, while the general public may appreciate that longterm behavioural responses such as stereotypies and chronic stress are ‘harmful’, there is
merit in understanding what animals prefer since as some scientists have noted, “we all
know which part (approach) will be the most powerful argument for the audience (general
public)”.