A pregnancy signal that works across species
The hormone collected from pregnant mares is commonly called equine chorionic gonadotropin, or eCG. A mare’s body makes it during pregnancy, and it can act on the reproductive systems of other mammals. In pigs and sheep, it is used in breeding programs to encourage eggs to mature and help bring females into reproductive readiness on a more predictable schedule.
That timing matters on farms. When many animals can be bred around the same period, producers can plan labor, housing, and the arrival of young animals more closely. In some protocols, eCG is paired with other hormones; it is part of managing a breeding cycle, not a universal switch that guarantees pregnancy.
The economic logic—and its tradeoff
The system links two very different kinds of farming. Specialized operations keep mares pregnant and collect blood containing the hormone; manufacturers process it into a product for livestock reproduction. The value comes from turning a naturally produced signal into a tool that can make breeding schedules more manageable in other species.
The arrangement also concentrates a welfare concern in the supply chain: the hormone depends on maintaining pregnancies and collecting blood from mares. How that is done matters to the animals, even though the product’s commercial purpose is to improve reproductive control in livestock. The breeding aid is possible because a horse’s pregnancy produces a signal that farmers can use to coordinate reproduction in other animals.
