Poor welfare occurs in situations in which the effects on the animal are adverse in that there is reduced fitness or clear indications that fitness will be reduced, ie. the animal is stressed, and in situations where the individual has difficulty in coping with its environment. Welfare is improved by increased control over the environment. There is a wide variety of measurements of welfare. Behaviour measurements are of particular importance but should be combined with physiological, immunological, injury, disease, mortality risk, growth and reproduction measures in order to obtain complete information. Suffering is an important aspect of poor welfare but welfare can be poor in the absence of suffering. There are many measures of poor welfare which do not necessarily indicate suffering. Welfare should not be defined solely in terms of subjective experiences.