What is animal welfare and how can we measure it?

Animal welfare can be defined as an individual animal's subjective experience of its mental and physical state as regards its attempt to cope with its environment. The mental state (feelings and emotions) of an animal cannot be measured directly, but has to be inferred from the behaviour, physiology, health and productivity of an animal. Various choice tests can be used to assess the behavioural priorities of animals. These tests provide insight into what animals regard as preferable or aversive. Unsuitable housing environments and management may lead to movement difficulties, abnormal responsiveness and abnormal behaviour. Also, a variety of responses of the neuroendocrine, autonomic nervous and immune systems can indicate coping difficulties and stress experienced by animals. Long-term stress may finally result in health problems and reduced productivity. Diseases and injuries themselves are naturally often coupled with suffering. Good productivity does not necessarily equal with good welfare while genetic selection for productivity, for example, may have negative welfare effects. Animal welfare is not only the absence of suffering, but also the animals' possibility to have positive mental states should be considered. Positive mental states can be interpreted from the behaviour and physiology of animals. Since the welfare state results from the complicated interaction of an animal with its environment, it is highly recommended that a diverse range of measures are used in animal welfare studies