Positive welfare indicators of the domestic pig (Sus scrofa domesticus), a review : Which of the indicators are being used for the on-farm evaluation of pig’s positive welfare?

Abstract: Since the 1960s the focus of animal welfare has been mainly on the negative aspects of welfare and on minimizing and alleviating these negatives. Lately, the focus has been not only on the negative features of welfare that should be kept above a minimum standard, but also on the positive ones that should be enforced. Positive welfare goes a step beyond the common welfare approach and focuses additionally on the positive aspects that animals should have in their lives. This review analyses the behavioral indicators that have been proposed as positive welfare indicators of the domestic pig and have been studied theoretically or experimentally. Various behavioral indicators have been proposed but play is the positive indicator that has been studied the most, followed by exploratory and social affiliative behaviors. Vocalizations and ear and tail postures have also been proposed as promising positive welfare indicators but more research is needed to clearly understand the expression of these behaviors and the affective states that they indicate. According to the literature results, the Welfare Quality protocol for pigs is the only protocol that evaluates the positive welfare of the pig on the farm level. Play, exploratory and social affiliative behaviors are being measured. In addition, positive emotions are being measured via Qualitative Behavioral Assessment (QBA).