It is now widely accepted that the concept of ”animal welfare” includes both the physical and mental wellbeing, and that providing positive experiences is equally important as avoiding and limiting negative ones. Most scientists seem to agree that horses experience positive welfare when exploring and feeding in complex environments and through friendly interactions with other members of the flock. In contrast, it is less clear in which situations they experience positive welfare when kept in captivity and their natural behaviours are restricted. We need indicators to assess if animals experience positive welfare, and the first aim of this thesis was a summary of the research on this subject presented the last decade. The indicators can be d...