Using aversion learning techniques to assess the mental state, suffering, and welfare of farm animals.

The extent that handling farm animals causes them to suffer is a central concern when assessing their welfare. "Suffering" is a mental state, resulting from different emotions, such as fear, pain, or boredom, which have different causes and effects on the animal's behavior and physiology. What is common is that they are aversive; animals will seek to avoid such experiences. The degree of aversiveness can be measured using behavioral techniques, which are based on an animal's ability to learn the predictive relationships between events. Compared with physiological stress responses, aversion learning techniques are more easily interpreted in terms of animal suffering and are more able to discriminate between handling treatments. They can sometimes be used to predict physiological responses to handling. The outcome of experiments in aversion learning can be affected by factors influencing the learning ability and memory of animals, and researchers need be aware of potential confounding in experimental design. Such techniques have been used to compare sheep handling practices, examine which components of transport are aversive for pigs and poultry, and examine the relationship between animals and handlers.