animal physiology and ethology. As early as 1964 the Brambell Committee acknowledged that “welfare is a wide term that embraces both the physical and mental well being of the animal”. The authors further elaborated that evaluations of animal welfare must take into account the scientific evidence derived from the animals’ structure, functions, and behavior (Brambell 1965; Duncan 2005). Although clinical signs can be used to assess physical well-being, and behavioral studies can provide information about animals’ preferences and cognitive state (for a review of validated animal models for fear and depression see Phelps and LeDoux 2005; also see Bateson and Matheson 2007), the Committee would like to emphasize that no physiologic measures exist to date with which to assess mental well-being directly. Nevertheless, discussions about animal welfare in the laboratory as well as in farm animal communities take into consideration a variety of criteria to assess an animal’s quality of life. It has been proposed that the most important consideration for the assessment of an animal’s welfare is its emotional state (Duncan 2005). Be that as it may, some of these criteria focus on the animals’ ability to experience pleasure and pain (as defined in Bentham 1879), or their higher cognitive capacities (Nuffield Council on Bioethics 2005), while others consider the animals’ housing and husbandry conditions. The latter are of course easier to define and to assess, and are therefore the focus of more scientific research and literature.

Housing and husbandry conditions should permit an animal to be physically healthy (i.e., not interfere with its biological functioning), live a natural life, behave more or less normally, and be free of pain and other negative circumstances (that induce negative affective states; Fraser et al. 1997).2 Concerns for animal welfare are often focused on what the animal may experience (Kirkwood 2007), including its ability to control its environment or predict the onset of a stressor. In these discussions, the term “suffer/suffering” is often used, albeit controversially due to lack of consensus with respect to the adverse emotional states to which it may allude, such as pain, distress, boredom, deprivation, fear, frustration, and grief, in which an animal may be said to suffer even for only a few minutes.3

Descriptors of an animal’s welfare are qualitative and range from “poor” to “good” (other adjectives commonly used include “negative”, “compromised”, “neutral”, and “positive”). Welfare may be compromised briefly (e.g., during handling, injection, or exposure to a predator) or over longer periods of time (e.g., in the solitary housing of a social species, or in the


For additional discussion of what is normal or natural with regard to laboratory animals, see Chapters 3 and 4.


The Veterinarian’s Oath outlines the moral obligation toward the alleviation of animal suffering by stating that “… I solemnly swear to use my scientific knowledge and skills for the benefit of society through … [in part] the relief of animal suffering….” (AVMA,

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