Effects of disease on farm animal welfare

Health is an important part of welfare and whenever an animal is diseased, welfare is poorer than when there is no disease. This point is often not recognised adequately by those studying animal welfare. Also, the full extent of the effects of clinically diagnosed disease on the welfare of the animal is seldom quantified. This quantification of the extent of poor welfare during disease is important for farm animals because of our general obligations to the animals. In order to fully evaluate the impact of housing conditions and management procedures on the animals and then decide what is acceptable, disease must be taken into account. One example of clinical disease conditions which are very significant causes of poor welfare concerns leg disorders such as tibial dyschondroplasia and femoral head necrosis in broiler chickens. A second example is the dairy cow in which the major welfare problems result from the various leg disorders and mastitis. A third example, in which there has been some quantification of effects on welfare, is sheep scab. For farm animals, other animals which we use, and for humans the evaluation of the extent of poor welfare during clinical disease is a major research area which needs to be developed.