The European reviewers used a conception of welfare that included affective states and natural living as well as basic health and functioning.
In these various quotations, then, we see a variety of concerns that can be grouped roughly under three broad headings: one centres on the affective states of animals, one on the ability of animals to lead reasonably natural lives, and one emphasizes basic health and functioning.
Some emphasize the basic health and functioning of animals, especially freedom from disease and injury.
Some scientists have used the basic health and functioning of animals as a basis for assessing and improving animal welfare.
The Australian reviewers based their analysis almost exclusively on the basic health and functioning of the animals, and they relied especially on what they called "widely accepted criteria of poor welfare such as health, immunology, injuries, growth rate, and nitrogen balance".
However, instead of the science providing a way to determine that one conception of animal welfare is correct and others are not, we see that the different scientists actually adopted the different value-based views of animal welfare – basic health and functioning, natural living, and affective states – as the rationale for different scientific approaches to assessing and improving animal welfare.
