Horses are highly social herd animals, and isolation or inadequate social contact is a major source of welfare compromise in domestic settings.
Social companionship is not a luxury for horses but a species-typical need whose deprivation causes genuine suffering. A horse in a single stable with no contact with conspecifics — the default situation for many performance horses — is experiencing a fundamental social deprivation that affects both its psychological state and its physical health. The argument that horses "get used to" isolation misidentifies chronic stress adaptation as acceptable welfare. Welfare-centered management provides meaningful social contact: ideally pasture-kept with companions, or at minimum visual and tactile fence-line contact. Individual differences exist — some horses form strong pair bonds while others integrate into groups — but the need for social interaction is universal.