Nurse mare foals are unfortunate foals born to mares that are bred solely for milk production. Nurse mare farmers use mares of varying breeds but often times the larger breeds, such as drafts, to breed nurse mare foals.
After foaling, the breeders lease the mares out to a farm, usually a farm involved with the horse racing industry. The mares are taken from their biological offspring anywhere between 1 day and 1 week of age. These new mothers then become mothers for more "expensive" foals. Their biological foals are left to die, are killed or are slaughtered due to the level care they require and the costs associated to raise the orphan foals..