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Prenatal care for a healthy mare and foal

Reprinted from the December 2014/January 2015 Issue of USDF Connection

By Natalie DeFee Mendik  

Whether you’re a first-time breeder looking for a foal from a favorite mare or an old hand in the business, breeding is a labor of love, not to mention a significant investment of time and funds.

Your goal: an uneventful pregnancy culminating in a healthy foal—and it starts with a mare in the best possible condition. With an eye toward the springtime breeding season, experts share their best practices for prenatal mare care.

Diet and Exercise

“I treat most pregnant mares like regular horses up to about five months of pregnancy,” says David Scofield, DVM, who’s board-certified in reproduction and based at Select Breeders Services-Veterinary Services, Chesapeake City, MD, a division of the international equine reproductive-services company Select Breeders Services.

To that end, Scofield recommends normal, non-strenuous exercise early in pregnancy to keep the mare conditioned. After five months, when most mares begin to “show,” pasture turnout provides adequate exercise for most, he says. Those that are overweight or need exercise because of insulin-resistant issues may benefit from walking and light trotting. “Professional broodmares” may just continue to enjoy pasture life, getting enough daily movement through turnout on large properties.

Nutritional needs early in pregnancy remain similarly straightforward, with a diet based on quality forage meeting the bulk of the mare’s nutritional needs.

“In early gestation, the fetus doesn’t really require any extra calories,” explains Scofield. “I keep my mares on a ration balancer, timothy, and alfalfa. A ration balancer offers minerals and vitamins without the added calories and carbohydrates found in pelleted grain; this allows you to manage weight while providing appropriate nutrition.”

As the mare’s pregnancy progresses, Scofield gradually increases the amount of alfalfa in the diet, which he recommends as an excellent source of protein for the growing fetus.

 “Normal grass hay has protein in the 8 to 10 percent range, whereas alfalfa offers protein from 15 to 20 percent, possibly even higher in some cases. This is a significant jump in protein that I think is important for the gestational mare,” he says. Alfalfa also contains higher levels of calcium, he adds.

This diet of rich legume hay, grass hay, and a ration balancer provides the mare with key nutrients. “Once mares start lactating, they are not going to be able to replenish their body stores,” says Scofield. “You want to make sure they are starting their lactation with a full complement in reserves of adequate fat, muscle, calcium and phosphorous; that’s what a ration balancer and alfalfa help achieve.”

A rough formula Scofield follows starts with a 50:50 mix of grass hay to alfalfa, slowly increasing the ratio of alfalfa to grass hay every month until the end of gestation, with most mares on exclusive alfalfa forage by foaling. With quality hay and a ration balancer, Scofield finds that additional supplements, aside from a salt-mineral block, are generally not necessary.

Located in central Florida, Belinda Nairn-Wertman’s mares have the good fortune to have access to grass pastures 24/7. The former dressage competitor—who represented the United States at the 1988 Olympic Games and many other championships—now calls Ocala home, where she and her husband, Bill Wertman, own Inspo, a Dutch Warmblood breeding and sales operation.

“When the pastures are good in summer, there’s no need to feed hay,” says Nairn-Wertman, who supplements forage with a high-fat, low-starch, low-sugar concentrate.

Starting in the fall when the pastures wane, Nairn-Wertman’s mares receive grass hay, gradually shifting to a timothy/ alfalfa mix as their pregnancies advance. Her program doesn’t include additional supplementation. “I don’t see the need for supplements when they’re on quality hay and concentrates,” she says.

 USDF gold medalist Kathy Priest is well-known in dressage circles as a successful FEI-level competitor, but she wears a second hat: Together with her equine-veterinarian husband, Dr. Gary Priest, she operates a 400-acre broodmare “nursery,” Woodspring Farm, in Versailles, KY. Although the operation formerly included warmblood breeding, now the broodmare end of the Priests’ business foals out about 30 Thoroughbred mares each year, with services from breeding through starting youngsters for the track and prepping for sales.

According to Kathy Priest, approaches to mare care are universal. “Whether you’re a small breeder or a large breeder, there’s not a whole lot of difference, because as far as the care goes, it’s pretty much all the same whether you have one or two foals or you have 25 foals.”

Being in the heart of Bluegrass Country, Priest’s horses, like Nairn-Wertman’s, enjoy 24/7 pasture turnout on large fields. “I think, first and foremost, we are blessed to be in a great area as far as raising horses, especially with our good grasses and good weather,” Priest remarks. “Our approach to nutrition is first of all good pasture, with good hay in the winter [a 50:50 grass-alfalfa mix]. We feed a 14-percent pelleted oat-based sweet feed that’s formulated for our area and soil, supplying the right amount of minerals and vitamins. Horses are foragers, so that piece is really important; you need a feed that supports what’s in your grass and hay.”

Maintain your mare at an ideal body weight—not too heavy, not too thin. “You don’t want a mare to be too fat. She’s pregnant and is going to be big, but extra fat deposits can make her uncomfortable when late in foal with a heavy fetus and can affect parturition,” says Scofield. “I try to keep mares at an ideal body condition of five to six. You can reduce alfalfa if the mare is too heavy.” He is referring to the well-known Henneke Body Condition Scoring System, in which a horse’s weight is evaluated on a scale of one (poor) to nine (extremely fat) according to body-fat assessments at the neck, shoulder, withers, back, and tail head.

Pasture turnout provides for both exercise and grass supplementation. But experts caution mare owners to keep a watchful eye out for fescues infested with endophyte, a fungus found on some fescue grasses. Ingestion of infested fescue can lead to fescue toxicosis, which can cause a variety of serious problems, including abortion and birth defects. Have your pasture checked, Scofield advises: Contact your county extension agent or send plant samples to a diagnostic lab, such as at the University of Kentucky. “They will give you a quantitative measurement and recommendations,” he says.

 An Ounce of Prevention

Supplement your mare’s regular immunization schedule with inactivated equine herpesvirus-1 (EHV-1, also known as rhinopneumonitis) vaccine, administered at five, seven, and nine months of gestation, Scofield recommends. In addition, isolate your broodmare population from horses that travel to shows, clinics, and other events.

“The biggest risk for a pregnant mare is equine herpes virus (EHV-1), which can cause the mare to abort,” Scofield says. “If you have horses that are coming and going to shows and the like, they can be exposed to the virus and come back and infect other horses on the property. I tell owners to keep the broodmare population separate from the horses that travel. No shared water, and keep a distance of at least 10 feet between fence lines.”

One month before the mare’s due date, administer pre-foaling vaccinations as recommended by your veterinarian.

 “Getting the right vaccines ensures the baby receives passive immunoglobulins [antibodies] from the mare’s colostrum [the mare’s milk secreted at parturition], passing protection onto the foal,” explains Scofield. “Those antibodies are what protect the foal in its first five to six months.” Based on the risk levels in your area, your veterinarian can advise you which vaccinations your mare should receive and at what intervals.

Deworming strategies for broodmares are familiar to any horse owner: biannual deworming of the herd for tapeworms and pinworms, plus fecal egg-count tests, in which fecal samples are checked under a microscope for worm eggs, followed by targeted deworming if needed. Larger facilities that cater to many horses may opt for a fi xed schedule of rotational deworming.

“We deworm our mares every 60 days according to season. A fecal count is a very good thing, especially if you have a small number of horses on a smaller property,” says Priest.

In addition, Scofield recommends deworming mares with an ivermectin-based product 24 to 48 hours post-foaling to prevent threadworm transmission in the milk. “These aren’t so common now but can cause diarrhea in foals,” he notes.


At about five months, Scofield performs a pregnancy check to make sure that the mare is still in foal. “Pregnancy loss from a heartbeat to parturition should be significantly less than 10 percent on a well-managed farm,” he says.

 Around seven to eight months, Scofield suggests, watch for signs of placentitis, an inflammation of the placenta, which can cause abortion. If your mare shows signs of premature udder development or vaginal discharge, contact your veterinarian.


Some mares with chronic conditions may need to stay on medications during their pregnancies. “A lot of the older warmblood population are insulin-resistant or have some sort of Cushing’s disease,” notes Scofield. He explains that, although medications such as pergolide may be acceptable in early pregnancy, the mare should be weaned off them closer to foaling so there is no effect on the foal; pergolide in late gestation can impact mammary development and the production of colostrum. Discuss any medications your mare receives with your veterinarian and form a long-term plan.

T Minus One

 The countdown is on! At about ten months of pregnancy, your foaling plans should be set. “Have a clear communication with your vet about foaling out. If you are taking your mare to a facility, do it optimally one month before she’s due,” Scofield says. “One month early allows the mare to acclimate to the facility, as well as develop antibodies to any of the flora of pathogens present in that environment; this increases the likelihood that the colostrum will contain antibodies specific to that location.”

Up to about ten months, Nairn-Wertman’s mares stay on pasture day and night, weather permitting. “The climate allows us to do that, which is great,” she says. “I think the best thing to do is to let them live as normal a life as you possibly can.” Within a month of foaling, the mares at Inspo are brought in at night in order to acclimate to spending time stalled. Nairn- Wertman takes their temperatures each day when they come in, which she has found useful in monitoring their status.

As foaling draws near, Priest recommends getting the mare settled into a comfortable, stress-free environment, preferably with a group of mares that will be foaling around same time. “Keep an eye on them in a pasture close to the barn,” she says, adding, “They do sometimes foal outside.”

 Think ahead to your long-term foal plans, as well. “Don’t raise a foal alone,” cautions Priest. “If you have just one broodmare and foal, partner up with a friend so you have at least two foals together. They need to be in a group outside, running and playing.”

Know Your Mare

”Get to know your mares,” recommends Nairn-Wertman. “I have older mares now that I’ve foaled for a number of years. If there’s something unusual, I’ll pick it up right away. If you have a new mare or are a first-time breeder, get to know your mares and learn their behavior. Keep a close eye on them; things can change quickly. Also, document things, so the following year you can look back at your records.”

Being familiar with each mare as an individual ties in with all aspects of their care. For example, Nairn-Wertman tailors each mare’s feed to her needs: One easy keeper gets a high-protein concentrate and grass hay, with alfalfa added to her diet only toward the end of gestation; another gives so much of herself to the foal that Nairn-Wertman likes to keep a little extra fat on her.

Enjoy the Journey

Vet your veterinarian to be certain you are on the same page regarding the pregnancy and birth process.

“Whether you’re in it for business or enjoyment, you have to work with people you like and trust, who give you straight answers,” says Scofield. “Form a dialog with your veterinarian so the process is as stress-free as possible.”

 On average, equine gestation lasts 320 to 360 days, with most mares foaling within 330 to 345 days of successful breeding. This gives you close to a year to enjoy being part of the broodmare process. Plan well, work closely with your vet, and prepare to welcome your own little bundle of equine joy!

Natalie DeFee Mendik is an award-winning journalist specializing in equine media. Visit her online at MendikMedia.com. 

Off to a Good Start  

Before you start dreaming about foal names, have your veterinarian perform a breeding soundness exam (BSE) on the mare you’d like to breed in order to evaluate her chances of conceiving successfully and having a healthy pregnancy. This best-case-scenario evaluation takes into account the mare’s history and overall health as well as gynecological issues. In addition to a whole-horse exam, your veterinarian will also check the mare’s external genitalia, vaginal region, and cervix via palpation, culture, and uterine biopsy.

According to David Scofield, DVM, of Maryland-based Select Breeders Services, many mares with dressage careers enter the breeding game in their late teens after retiring from competition. A BSE can help uncover any potential roadblocks that may come as a surprise to the novice breeder, allowing a glimpse into the mare’s probability of successfully carrying a foal to term. Scofield also recommends performing a BSE on any mare being purchased for breeding purposes.

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