Induced Lactation in Horses: How Professional Nurse Mares Save Orphan Foals

Induced lactation in nurse mares is a veterinary process that uses hormonal therapy to stimulate milk production in mares without requiring pregnancy. According to providers like Nursemares of Kentucky and ColdSpring Nurse Mares, this method allows orphan or rejected foals to receive maternal care and nutrition without the ethical cost of separating biological foals from their mothers, a practice common in traditional nurse mare farms.

How Hormonal Induction Replaces Traditional Nurse Mare Farms

For decades, the “nurse mare” industry relied on a controversial system where mares were bred specifically to produce milk. Once lactation began, the biological foals—known as “nurse mare foals”—were removed and often ended up in rescue organizations or were euthanized. The Kentucky Humane Society describes nurse mare foals as foals born so that their mothers can produce milk for other little ones.

Modern facilities now use pharmacological protocols to bypass this cycle. By utilizing a combination of estrogens, progestogens, and prolactin-stimulating drugs (such as domperidone or sulpiride), veterinarians can trick a mare’s endocrine system into believing she has undergone a pregnancy. This allows retired broodmares to serve as foster mothers without ever producing a biological offspring that would be displaced.

The Science of Inducing Milk Production

The process focuses on reproducing the hormonal sequence of pregnancy to trigger the mammary glands. According to protocols used by industry leaders, the ideal candidate is an experienced former broodmare with a proven maternal temperament. The typical process includes:

• Hormonal Treatment: Administration of substances to stimulate the mammary tissue.
• Physical Stimulation: Regular milking or massaging of the udder to encourage milk flow.
• Production Monitoring: Mares are generally considered ready when they produce between 3 to 5 liters of milk per day.

Laura Phoenix, founder of Nursemares of Kentucky, indicates that achieving a reliable and abundant milk supply typically takes 11 to 14 days. To ensure immediate availability during the peak foaling season, these organizations maintain a rotation of mares at different stages of the protocol—some fully lactating, some in treatment, and some resting.

The Grafting Process: Bonding the Foster Mare and Foal

Producing milk is only half the challenge; the mare must also accept the foal as her own. This process, known as “grafting,” involves several behavioral and physiological triggers to prevent the mare from rejecting the stranger. According to ColdSpring Nurse Mares, these techniques include:

• Scent Transfer: Using towels or equipment impregnated with the mare’s scent to rub onto the foal.
• Oxytocin Release: Veterinarians may stimulate the cervix and vagina to trigger the release of oxytocin, the hormone associated with maternal bonding.
• Supervised Introduction: Gradual presentation of the foal and assisted first nursing sessions to ensure the mare doesn’t react aggressively to the foal’s energetic suction.

The success rate for these pairings is high. Laura Phoenix reports a success rate near 98%, noting that if a specific pairing fails, the personnel try to solve the problem or provide another mare.

Comparing Induced Lactation vs. Human Raising

Research, including a study conducted at Walnut Hall Ltd. in Lexington, Kentucky, suggests that foster mares provide critical developmental benefits that human-led bottle feeding cannot replicate. The study found that Standardbred foals raised by induced-lactation nurse mares maintained the same auction value as those raised by biological mothers.

Beyond nutrition, the “socialization” aspect is vital. A nurse mare teaches a foal the social signals of the herd, such as appropriate distance and boundaries. Foals raised exclusively by humans often develop issues, such as biting or jumping that they would normally reserve for other horses.

Critical Limitation: The Colostrum Gap

Despite the effectiveness of induced lactation, there is one biological wall: induced lactation does not produce colostrum. Colostrum is the first milk produced after birth, rich in antibodies essential for the foal’s immune system.

Because the nurse mare did not undergo a natural pregnancy and birth, she cannot provide this initial immune boost. According to veterinary standards, any foal moved to a nurse mare must first receive colostrum via:

• Stored, screened colostrum from another mare.
• Hyperimmune plasma administered intravenously.

Summary of Nurse Mare Services

As veterinary medicine evolves, the shift toward induced lactation removes the ethical dilemma of the “nurse mare foal,” providing a sustainable path for orphan foals to thrive under the care of professional foster mothers.