Welfare in relation to feelings, stress and health

Abstract
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 farmers and other animal users keep and treat animals. Welfare can be defined in a way which incorporates ideas about needs, feelings, stress and health. The scientific assessment of animal welfare has developed substantially and very many studies of different kinds of animals have been carried out. Information from such studies is used by legislators, food companies and the public with the consequence that the various kinds of regulation lead to real improvements in animal welfare. Health is defined as an animal's state as regards its attempts to cope with pathology, where pathology is a detrimental derangement of molecules, cells, tissues and functions that occur in living organisms in response to injurious agents or deprivations. Pathology can be classified into: genetic abnormalities
physical, thermal and chemical injury
infections and infestations
metabolic abnormalities
and nutritional disorders. Health is a part of welfare. When an animal's health is poor, so is its welfare, but poor welfare does not always imply poor health. There are some measures of poor welfare which are classified as pathology and will therefore also be indicators of poor health, including body damage and symptoms of infectious, metabolic and nutritional disease. Other measures of poor welfare, whilst not being signs of poor health at that time, indicate a risk of poor health
in the future. They include immunosuppression and the occurrence of injurious abnormal behaviours. These are causal links between poor welfare and poor health. Two pathways can be identified:
A. chronic activation of physiological coping mechanisms ---> immuno-suppression ---> infectious disease
B. behavioural coping mechanisms ---> injurious abnormal behaviour ---> physical injury. The connection between physiological coping mechanisms, immune function and susceptibility to infectious disease is complex. Different environmental challenges elicit different neuroendocrine responses
and different species and individuals may respond differently to a given challenge. Furthermore, a given neuroendocrine response has different effects on different leucocyte populations, with the consequence that susceptibility to some
pathogens is enhanced, whilst susceptibility to others is reduced. It is therefore necessary to consider one challenge, one species and one pathogen at a time. Abnormal behaviours include redirected behaviours, stereotypies and heightened aggression. The redirection of behaviour is a coping mechanism and hence a sign of poor welfare. Stereotypies and heightened aggression are either coping mechanisms or behavioural
pathologies and also indicate that welfare is poor. Some of these behaviours are injurious, either to the animal itself or to other animals in the group. They can therefore lead to poor health. Abnormal behaviours associated with indoor housing or intensive husbandry systems where welfare is poor, which lead to increased risk of poor health, are listed. These include redirected behaviours, stereotypies and heightened aggression, as well as other abnormal behaviour patterns whose causes are as yet unclear. A large number of potentially injurious abnormal behaviour patterns have been identified. It is concluded that there are several routes by which poor welfare results in an increase in disease. The pathophysiology of states typified by behavioural abnormalities and emergency physiological responses is a subject which is insufficiently investigated.