Why do pigs root and in what will they root?: A review on the exploratory behaviour of pigs in relation to environmental enrichment

The intention of the new European legislation on rooting materials for pigs is to improve the welfare of pigs. The question is: which materials are suitable rooting materials for pigs? To answer this question the motivation for exploration in pigs is elucidated and the needs of the pigs in this context are discussed. The effects of different materials on the behaviour of pigs are listed and the preferences of pigs for numerous different materials are compared. Based on the literature on the normal behaviour of pigs and studies on pigs’ use of and preferences for various materials, we conclude that in order to be a suitable rooting material the material must stimulate the exploratory behaviour of pigs for an extended length of time. Exploratory behaviour in pigs is best stimulated by materials that are complex, changeable, destructible, manipulable, and contain sparsely distributed edible parts.