Making Mommy Happy

As part of our special breeding issue, here is a look at how to best prepare your mare for breeding season.

Here comes the broodmare, shaking herself off after her hot-tub soak, nibbling rich, gourmet grass and crunchy feed off a shiny silver tray and daintily sipping Evian bottled water as she watches “Broodmare Idol” on her flat-screen TV. Now it’s time for her massage.

Some of us go to great lengths to ensure mare moms-to-be are pampered, but a happy mare usually leads to a happy foal. Here are the programs several experts follow to get ready for breeding.


Biology 101 teaches us that all living things are products of heredity and environment, and the careful, thoughtful breeding of horses reminds us of just that. Consider how it’s done at Iron Spring Farm in Coatesville, Penn., revered for both its dressage horses and jumpers. Robert Croteau is in his thirteenth year as equine manager, calling the breeding shots for the farm’s own band of broodmares and outside mares.

The most important task is managing changes in the environment, says Croteau. When possible, he advocates “keeping the horses outside and replicating the natural social order.” Think less stress. That means being aware if a new mare isn’t readily accepted, and then making better arrangements for her. Maybe she’s more finicky, high-strung or just isn’t settling in. Maybe she’s bottom-of-the-ladder and “risks getting kicked to the point she slips (aborts). Change her social structure and move her. Be a good agriculture-based farmer, growing quality horses,” says Croteau, who urges taking stewardship seriously. “You’re dealing with Mother Nature, always breeding for the best possible outcome.”

A mare needs to positively adapt to the physical environment too, he believes, which will allow her to be less susceptible to invasive viruses and detrimental microbes. Once adapted, “the immune system rises to the challenges,” Croteau says.

When temperature and climate permit, natural forage (grass pasture) is preferable, augmented with quality hay. Croteau’s gestating mares receive a light alfalfa/grass mixture: “Eighty percent of the diet should be forage,” he says, eschewing supplements except for horses living in a mineral-depleted geographical area. “Fields appropriately fertilized, analyzed, not overgrazed and properly rotated” always pay off in the end. His turned-out horses do have access to salt blocks.

Croteau monitors his mares’ physical condition regularly. Use your eye to observe body condition and weight, he advises, to spot even minute changes. In addition, Croteau weighs his horses at least every month; mares with foals weigh in weekly until weaned. He cites the useful Body Condition Score (see box, page 28)—developed at Texas A & M University—and its gradients 1 to 9. “Nine would be obese, while ‘normal’ is five to seven,” he says.


Breeding is not just a science but an art, says Dr. John Steiner, DVM , president of the American College of Theriogenologists (reproduction) and esteemed partner at Hagyard Equine Medical Institute in Lexington, Ky. For a horse to reproduce, just like people, “we want them in the best possible shape,” he says.

Steiner supports exercise: “They can be ridden until five or six months along.” He too avoids supplements—except those indicated for joint care. As for hormones, he proffers this advice: “When we get to breeding season, we may want to control the heat cycle. Depending on when we get semen or when we want to breed, we might use various combinations of progesterone and/or estrogen, but it’s not the best thing long-term.”

If heat cycles aren’t manipulated, mares will come into heat naturally at the end of March or April. “The best time for breeding is May or June, as far as fertility; that’s what happens in the wild,” Steiner notes.

As we know, most Thoroughbred breeders want their foals to be born as close to Jan. 1 as possible. For that reason, Steiner says, empty mares are placed on an artificial lighting program providing a total of 16 hours of natural and artificial light. This mimics the longer days of mid-spring that trigger the heat cycles in the mare. Sixty days under lights will get most mares started, so December 1 is frequently the date to begin.

Trend-wise, Steiner sees more use of artificial insemination occurring in sport horses—it’s not allowed in Thoroughbreds—and he also documents more use of frozen semen.

Like Croteau, Steiner watches closely for health issues. A breeding soundness exam is never a bad idea, he says, along with a focus on the basics: regular deworming, vaccinations and teeth floated in concert with your veterinarian. “It’s important to avoid viral abortion,” cautions Steiner, so be aware of risks in your particular geographic region. Discuss with your veterinarian which vaccines can prevent those infectious diseases most threatening to the baby, such as rhino, equine viral arteritis and leptospirosis, among others.

When is your mare most at risk? At, the equine experts at Bayer caution that the earliest days of an embryo’s existence are somewhat risky. The first 30 days carry a 10 to 15 percent chance that the embryo will be resorbed or aborted. “Stress, illness, uterine infection, hormonal abnormalities, the presence of twins, and other factors have been implicated in early embryonic loss…Illness and/or fever can cause the mare’s system to secrete prostaglandins, which may cause abortion. “Other Bayer tips include 1) transport your mare only if necessary, and 2) use caution when exposing your mare to other horses. Avoid any undue risk of injury or disease transmission.


“The more you treat them like a horse, the better they’ll be,” says Dr. Leea K. Arnold, DVM, who sees hundreds of mares annually at Arnold Reproduction Center in Weatherford, Texas. She notes that “you don’t just breed a mare one time and she gets in foal and that’s the end of it. You have to plan to breed her as close to ovulation as possible, you have to palpate her, ultrasound her….”

Arnold likes zinc and antioxidants such as vitamins A, D and E for broodmares. “Most feeds have adequate supplies,” she says, but always read your labels if you’re not sure.

Her theory on hormones is to “stay as far away as possible.” Like Steiner, she prefers to regulate the heat cycle via lighting. “Bring her in and put her under the lights at the beginning of December, then you know she’ll be cycling the middle of February when breeding season starts,” Arnold advises.

Arnold is not a fan of Regumate (progesterone), unlike some owners. “You’re messing with Mother Nature; it confuses the horse,” she says. “The Chinese believe it’s harmful; it causes stagnation, lack of blood flow that could adversely affect reproduction.”

Most mares make good broodmares, adds Arnold, unless the horse is exceptionally foul or ill-conformed. Matching is key: If you breed a big-headed mare to a little-headed stallion, “you’ll breed to correct that mare’s fault. Don’t breed like to like.”


At Willie’s Last Resort near Columbus, Ohio, Sara Riegel has handled her fair share of mares and babies—and very successfully. Her mares live contentedly outside with protective sheds, as do Croteau’s, and she supplements with hay and grain if needed. Riegel likes a complete feed with 14 percent protein and a little higher fat content; she adds free-choice salt and always—it almost goes without saying—clean, fresh water.

She also advises to keep ’em going and active if appropriate. Riegel continued to show her mare through most of her pregnancy. However, she cautions, “Don’t start a sudden exercise or riding regimen if the horse isn’t used to it, or you’ll risk losing the foal. A leisurely trail ride is great!”

Unlike some of our other experts here, Riegel sees some uses for hormones. She supports “supplementing with progesterone to hold the pregnancy after they’ve been bred.” She likes HCG for aiding the mare ovulation process, which, at $15 to $20 a dose, isn’t financially prohibitive. But it doesn’t always work, so repeat endeavors may be indicated.

Your “nursery” can have an effect on mother and baby, says Riegel, so she pampers both mom and baby with a stall “that’s bigger than average, quiet with a bit of privacy, bedded with straw versus sawdust.” Oh, and the radio plays music in her barn, to soothe these not-so-savage beasts.

Yes, some pampering is a good thing. Your broodmare wants to listen to Beethoven’s Fifth or the Dave Matthews Band? Her champagne flute is empty? Okay on the first request, but remember: no alcohol during that eleven-month pregnancy!






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