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Nurse Mares Provide Crucial Service to Breeding FarmsBy Kentucky Equine Research Staff · November 15, 2003

Dixie. Belle. Big Mama. Simple enough names for the mares in the small band. A quick glance reveals nothing out of the ordinary; the mares and their foals seem completely content devouring their hay this chilly spring morning. But there is something extraordinary about these matrons, something so special that they're revered by breeders everywhere. In fact, these mares are on call, biding their time until their unique services are required, in much the same way human physicians readily respond to beeping pagers and ringing cell phones. And just like those physicians, these mares are in the business of saving lives, those of orphan foals.


Owners of nurse mares provide an indispensable service to the horse-breeding community. When foaling goes smoothly, the outcome is an energetic foal and an attentive mare.


Unfortunately, however, foaling often results in a perfectly healthy foal and an imperfect mother. Sometimes the mare fails to produce milk or refuses to nurture her foal. Rejection by the mare may take several forms. Some mares will nuzzle and lick a foal but will not allow it to nurse. On the opposite end of the spectrum, other mares become vicious after foaling and will bite the foal's neck, shake it, and attempt to throw it to the ground. In other instances, mares die from the trauma of foaling. When any of these predicaments arise, management of the motherless foal presents a sizable challenge.


The owner is typically left with two options, bottle-feeding the foal or acquiring a nurse mare. Many orphan foals have been successfully bottle-fed, but hand-rearing is a considerable undertaking. During the first week of life, for instance, foals must typically be fed every two hours. Equine behaviorists believe it best to have a mare raise an orphan foal. Not only will the foal be healthier and more robust because of the antibodies contained in mare's milk, but the foal will be better socialized to other horses. Hand-raised foals, particularly colts, often become difficult to manage because they are not respectful of people. Nurse mares are an incredible labor-saving resolution.


Mares of draft or draft-cross breeding are often used in the nurse mare trade because they have strong maternal instincts, provide plenty of milk, and rarely reject a foal. Mild-mannered mares of other breeds, such as Paints, Appaloosas, and Quarter Horses, have also proven to be exceptional foster mothers. One now-retired Appaloosa nurse mare in Washingtonshowed phenomenal commitment to her trade. She reportedly raised 20 Thoroughbred foals, in addition to 17 foals of her own. In some years she mothered two foals simultaneously.


Milk on Demand?

Can mares produce milk without foaling? According to French scientists, it's possible. Building on previous studies, a research group led by Peter F. Daels, DVM, PhD unveiled a method for induction of lactation in mares without corresponding pregnancy at the annual convention of the American Association of Equine Practitioners late last year.


For a period of two weeks, Welsh pony mares were given a precisely calculated mixture of estrogen and  progesterone, coupled with a dopamine D2 antagonist such as sulpiride or domperidone, the product often used to counteract fescue toxicity in late-term pregnant mares and to boost milk production in mares with little milk at foaling. All of the mares in the study had given birth and nursed at least one foal in preceding years. A milking machine designed for dairy goats allowed the collection of milk five times per day and was begun nine days after the commencement of the treatment.


In a second though closely related study, mares were given the same treatment as previously described, but milking was delayed until the end of the second week in an attempt to pool colostrum, the antibody-rich milk secreted by mares immediately following typical foaling. No significant differences in milk yield occurred between the two studies. Measurement of antibodies in the milk during the first two days of collection revealed low levels, indicating mares are unable to produce colostrum when lactation is artificially activated.


An offshoot of the aforementioned studies determined the growth rates of foals adopted by mares with induced lactation. Sixteen newborn foals and three seven- day-old foals were successfully united with mares in the study. Fifteen foals remained with their natural mothers and served as controls in the study. All foals were weighed at birth, at 14, 30, 60, and 120 days of age, and at weaning. While differences were noted in initial growth rates, none were documented in adopted and control foals by weaning.


Raising an orphan foal is a formidable task. Often nurse mares are difficult or impossible to acquire during emergency situations, and bottle-feeding an orphan foal requires a significant commitment of time and resources. The advantages of inducing milk production in mares are numerous, though this technology is likely years away from day-to-day use by veterinarians and horsemen alike.


Safety First

Once the decision has been made to lease a nurse mare, several key steps should be followed. Although few risks surround the acquisition of a nurse mare, those that loom can be devastating. The primary concern, beyond that of her disposition and willingness to accept a foal that is not her own, is the nurse mare's health. While the urgency of the matter may seem to outweigh the importance of health documentation, foal owners should insist on a vaccination and deworming history of the mare, in addition to test results for equine infectious anemia (negative Coggins test).


Foal owners may also require a nurse mare to have a comprehensive immunization battery, not simply bare-bones vaccinations. A vaccination for strangles, for instance, is not one typically given to broodmares, but imagine the widespread implications of a strangles outbreak at a Thoroughbred nursery. This is precisely what happened on one Japanese stud. A nurse mare was diagnosed with strangles after being introduced to the farm. As a result of her infection, three foals and four yearlings developed clinical signs of strangles within the next six weeks and required costly veterinary treatment. Once the nurse mare arrives at the farm, she should be kept away from other mares for at least seven days and preferably 21 days. This precaution will protect resident horses from the spread of pathogens, including equine herpes virus-1, which could cause a storm of abortions.


A once-over by a veterinarian is also imperative, particularly if the mare was delivered with little history of preventive medicine. The veterinarian can formulate an appropriate vaccination and deworming protocol that dovetails with procedures already in place on the farm. Mares that will be bred to teasers, stallions maintained on breeding farms to detect estrus and jump maiden mares, should be vaccinated against equine viral arteritis (EVA), a highly contagious disease.


Of course, accurate record keeping is a reciprocal kindness. Horsemen who utilize nurse mares should be able to document all health care given while the mare was providing her services at the foal owner's farm. Cooperation between the owners of the foal and the nurse mare will also prevent duplication of vaccinations and deworming.



Nurse mares are well aware that the babies introduced to them are not their own, but their willingness to adopt a foal is a compliment to their disposition and maternal instincts. Mares are typically placed in specially designed stocks or are otherwise restrained while the foal nurses the first few times.


Particularly docile mares may only need to be restrained through a few nursing bouts before being turned loose with the foal. The mare and foal should be observed carefully for several hours to ensure the bond between them is established. Once acceptance is achieved, most nurse mares will then treat foals as their own.


The Question of Overnutrition

Draft mares usually produce abundant quantities of milk. As such, there has been a suggestion that draft mares may not be the most appropriate foster mares for foals of light horse breeding such as Thoroughbreds and Standardbreds. Milk production is thought to be directly correlated to body weight; mares provide approximately 3% of their body weight in milk to their offspring each day. Therefore, a typical 1,300-pound Thoroughbred broodmare may generate 39 pounds of milk. If a Thoroughbred foal is weaned onto a draft mare that tips the scales at approximately 1,800 pounds and is capable of producing 54 pounds of milk daily, what effect will this have on the foal?


The growth rate of foals is dependent on energy and protein intake. Rapid growth rate resulting from overconsumption of these nutrients may predispose foals to skeletal problems including osteochondritis dissecans.


In a study conducted by Kentucky Equine Research, growth rates of foals raised on nurse mares were compared to growth rates of foals raised on their natural dams and growth rates of foals weaned at five days of age and fed milk replacer. The foals raised on nurse mares were larger than the other groups of foals at the end of at the six-month study, and they grew faster during the first three months of age.


The stage of lactation of the nurse mare is also a pertinent consideration. In addition to antibody levels, mares produce more protein and lipids in their milk immediately following foaling. These levels decrease over the ensuing weeks. For example, the protein content of mare's milk drops from 2.7% during the first month of lactation to 1.8% during the fourth month. If a newborn foal is placed on a nurse mare in her fifth month of lactation, the mare's milk may not contain adequate quantities of essential nutrients.


The Bottom Line

Mare owners often pay about $1000 for the services of a nurse mare, with some suppliers collecting more for a one season lease. Of course, the mare owner is responsible for caring for the mare throughout lactation, so any blacksmith, veterinary, and feed expenses must be figured into the final calculation. But this is a pittance considering that many foals placed on nurse mares may be worth thousands and perhaps millions of dollars.


In addition to everyday expenses, mare owners are expected to return the mare in foal. The owners of nurse mares are usually not particular about what stallions are used for rebreeding. Teasers are generally used to breed back these mares.


Raising foals is a life-enriching experience for many horsemen. More likely than not, the services of a nurse mare will not be required. When nurse mares are needed, however, they truly offer compromised foals a link to life.

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