Quality of life means welfare: how is it related to other concepts and assessed?
Our view of which individuals should be the subjects of our moral actions is expanding to include more people and more species. Animal welfare is the subject of rapidly increasing concern in most countries in the world, and this concern is resulting in changes in the ways in which animal
users keep and treat animals. Ethical decisions about whether the killing of an animal is justifiable should be considered separately from those about how poor welfare can be and still be acceptable. The term 'euthanasia' should be restricted to killing an animal for its own benefit. Quality
of life (QoL) in humans is generally taken to include: physical condition and any impairment of this resulting from injury or disease; capacity to function; perception of functioning; and satisfaction with functioning in relation to what is believed possible. If the welfare of an individual
is its state as regards its attempts to cope with its environment, then welfare is essentially the same as QoL. Both include the state of the individual's coping systems, including those responding to pathology, various behavioural and physiological responses, and cognitive processes associated
with suffering or pleasure. Hence, both welfare and QoL include health and the extent of positive and negative feelings. Many papers referring to animal welfare include objective quantification whilst few papers referring to QoL do so. Some human studies assess QoL by the less objective method
of questions asked of subjects. Neither QoL nor welfare should be assessed using solely subjective measures. Assessment of welfare must take account of the wide variety of coping systems and coping strategies used. A range of measures including those of behaviour, physiology, brain function,
immune system function, and damage is needed. The ease or difficulty of coping should be interpreted within the framework of the abilities of the animal. Animals with more sophisticated cognitive functioning may have the best abilities to cope with problems. The scheme presented here for assessing
welfare over time facilitates ethical decisions regarding whether welfare is good or whether it is unacceptably poor.