The tail as an iceberg indicator: interrelationships with welfare problems

This chapter addresses the need for animal welfare indicators that can be easily and quickly implemented. Using the theoretical concept of an iceberg indicator, this chapter develops a model for the assessment of domestic pig welfare that focuses on rearing and fattening pigs. The model assumes that the tail serves as a proxy for tail biting behaviour, which is associated with several aspects of sustained problems in pig production (i.e., underlying risk factors). The proposed complementary tail-based indicators are tail posture, tail lesions, and tail length. They provide an initial qualitative assessment of overall animal welfare status. These indicators are important because there is an urgent need for rapid and reliable protocols to assess pig welfare. Tail-based indicators help identify the extent of underlying welfare problems so that they can be quickly addressed. Although these indicators do not yet allow us to draw conclusions about positive welfare, a curled, intact tail is desirable as it provides an animal-based measure of better/improved welfare relative to other tail conditions and postures. While it may be difficult to fully utilise the model at this time given the high prevalence of pigs with docked tails, it has the potential to be implemented in a variety of pig production systems and across countries to assess and subsequently improve the overall welfare status of commercially housed pigs.