Horses are highly social animals that suffer when isolated. Managing the welfare needs of horses kept singly requires specific interventions to reduce isolation stress.
A horse kept without equine companions is experiencing chronic social deprivation - a welfare compromise that affects its psychological wellbeing every day. The impacts range from mild increased anxiety to severe separation distress, stereotypy development, and health problems driven by chronic stress. The welfare solution is a genuine equine companion wherever possible. Where this is genuinely impossible, companion animals, visual contact with other horses over a fence, and maximizing human social interaction provide partial mitigation. Isolation is never welfare-neutral for a horse.