Pregnancy is a crucial time for a mare and her unborn foal's health.
Proper nutrition is vital to maintaining the mare’s health and has a direct impact on the foal’s development, influencing its growth, overall health, and long-term soundness. Knowing what to feed and what to avoid is essential whether preparing for breeding, managing gestation, or planning for nursing.
This guide covers the fundamentals of broodmare nutrition, key nutrients, supplements, feeding tips for pregnant mares, and common mistakes.
Why is a Pregnant Mare's Diet Important?
Proper nutrition is essential when preparing mares for breeding and becomes even more important throughout pregnancy. During gestation, mares usually gain between 12% and 16% of their starting body weight to support fetal growth and placental development.
Historically, it was commonly believed that early pregnant mares could be fed the same as open mares until the final 3–4 months of gestation. However, research now suggests that this approach may increase the risk of the foal developing Developmental Orthopedic Diseases (D.O.D.).
Trace minerals, many of which are crucial for proper bone development—are stored in the liver of the developing fetus. Inadequate nutrition during gestation may prevent the mare from providing enough nutrients to the foal during the final trimester, when fetal growth is at its peak.
Many pregnant mares can maintain or even gain weight on good-quality forage, but forage alone doesn’t provide all the nutrients they need, especially trace minerals that are necessary for the growing foal. When these minerals are lacking, the fetus pulls from the mare’s nutrient stores, which can become depleted over time. This not only increases the risk of Developmental Orthopedic Diseases (D.O.D.) in future foals but may also impact the mare’s long-term health and fertility. That’s why it’s critical to carefully manage a broodmare's diet from conception through foaling.
Assessing a mare’s caloric needs is relatively easy using body condition scoring, but checking her trace mineral and antioxidant levels is more complicated and often overlooked. Providing the proper nutrition throughout pregnancy is key to supporting healthy fetal development, the broodmare's health, and giving the foal the best possible start in life.
What to Feed a Pregnant Mare
Feeding your pregnant mare a well-balanced diet helps support the health and well-being of both the mare and her foal throughout pregnancy, birth, nursing, and the foal’s early years. The foundations of a well-balanced diet for pregnant mares include certain trace minerals, antioxidants, and the ideal amount of calorie intake.
Providing Key Nutrients: Trace Minerals & Amino Acids
The nutrients that are most commonly found to be imbalanced or deficient in pregnant mares include:
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Essential amino acids
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Calcium-to-phosphorus ratio (particularly when feeding legume-based forage, such as alfalfa)
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Copper and zinc
Ensuring broodmares are being fed the right balance of these key nutrients is an essential part of feeding pregnant mares. A particular focus should be on maintaining the optimal amino acid balance and the levels of key trace minerals, such as copper, zinc, and possibly manganese, when feeding pregnant mares.
According to the Nutrient Requirements of Horses (NRC, 2007), the daily recommendations for copper and zinc are 100–125 mg and 400 mg, respectively. However, some studies indicate that increasing copper to 350 mg and zinc to 800–1,000 mg per day may help reduce the risk of Developmental Orthopedic Diseases (D.O.D.).
The NRC (2007) guidelines highlight lysine as the most essential amino acid for horses. Although overall protein recommendations haven’t changed from earlier editions, the increased lysine requirements reflect a greater focus on protein quality—that is, the specific amino acids provided, rather than just the total amount of protein in the diet.
Vitamin E and Selenium
Vitamin E is another key antioxidant in the equine diet, playing a vital role in supporting both the mare's and foal’s immune defenses. Ensuring adequate Vitamin E intake during pregnancy can improve the passive transfer of immunoglobulins through the colostrum—the mare’s first milk.
Studies show that mares supplemented with 2,500 IU of Vitamin E during the final five weeks of gestation produced colostrum richer in both Vitamin E and immunoglobulins. This enhanced nutrient profile can help strengthen the newborn foal’s immune system.
Selenium is also a vital antioxidant that supports reproductive health in mares. Because forage selenium levels vary by region, a forage analysis is key to determining accurate selenium levels. Although a mare's pregnancy doesn’t increase selenium requirements, ensuring her selenium needs are met, especially in conjunction with vitamin E during late gestation, can improve reproductive outcomes, boost selenium levels in colostrum and foals, and help prevent white muscle disease. Selenium needs can be met by feeding a horse feed specifically designed for pregnant mares; it should not be supplemented separately without bloodwork confirming a deficiency.
Balanced Calorie Intake
The broodmare should ideally be at a body condition score of 5-6 coming into foaling. To minimize excess calories and prevent obesity in pregnant mares while still meeting their nutritional needs, specially formulated products known as ration balancers are often used.
These products contain three to five times the levels of essential amino acids, major minerals, trace minerals, and vitamins compared to most low-cost horse feeds intended to be fed in larger amounts. Ration balancers provide the nutritional equivalent of six to ten pounds of typical horse feed—but without the added calories. High-quality ration balancers are typically tailored to complement the specific type of forage in the horse’s diet, whether it’s grass, a grass/legume mix, or pure legume hay.
Maintaining Gut Health
A healthy gut is paramount for any horse, but especially for pregnant mares.
A valuable supplement to consider during pregnancy is Constant Comfort® Plus, a comprehensive gut health formula. More than just a stomach buffer, Constant Comfort® Plus supports the entire digestive tract. It includes soothing ingredients such as aloe vera, glutamine, and lecithin to protect the stomach lining, along with seaweed-derived calcium to help maintain a healthy stomach pH. This supplement also features Equi-Ferm XL®, a pre- and probiotic blend that promotes overall digestive and immune health. For optimal results, it’s recommended to pair Constant Comfort® Plus with the Constant Comfort® Block.
Additionally, yeast supplementation in pregnant mares has been shown to increase antibody levels in colostrum, enhancing immune protection for the newborn foal, according to one study.
Omega-3s and DHA
Although not classified as an essential nutrient, supplementing pregnant mares with docosahexaenoic acid (DHA)—a marine-sourced omega-3 fatty acid—can provide significant benefits for both the mare and the foal.
Research shows that DHA crosses the placenta and reaches the fetus. One study even found higher levels of circulating DHA in foals born to mares supplemented with DHA, and that mares given DHA during the final trimester experienced faster uterine recovery after foaling. Their foals also stood and began nursing sooner than those from unsupplemented mares. In humans, DHA supports visual and cognitive development, and similar neurological benefits may extend to developing foals.
One effective way to provide omega-3s is by feeding Wholesome Blends® Omega Plus, Omega-3 Oil Supplement. This natural anti-inflammatory supplement is rich in omega-3 fatty acids and features a blend of hemp, canola, and flax oils. It supports a healthy coat, body condition, and immune function and aids in recovery after exercise.
Another way to provide both omega-3s and DHA is by feeding Natural Remedy®, a natural anti-inflammatory supplement. Natural Remedy delivers DHA, a powerful omega-3 fatty acid that helps naturally reduce inflammation while supporting immune health, cardiovascular function, and respiratory performance.
What Not to Feed a Pregnant Mare
When feeding your pregnant mare, it’s essential to avoid or limit certain types of feedstuffs and ingredients. Some of these contain compounds that can disrupt the mare’s normal hormonal balance, potentially leading to complications during pregnancy, birth, or lactation.
Overfeeding
Although pregnant mares require increased caloric intake, overfeeding, particularly with horse feeds high in nonstructural carbohydrates (NSCs), can cause complications for both the mare and the foal. Excessive weight gain may also hinder proper fetal development and increase the risk of insulin resistance in the mare.
Certain Herbs & Ingredients
While it’s essential to consult with an equine nutritionist before introducing herbs into a pregnant mare’s diet, some herbs and ingredients that should typically be avoided during pregnancy include:
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Chasteberry
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Chamomile
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Garlic
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Turmeric
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Raspberry leaves
Unbalanced Mineral Ratios
Pasture grass alone often fails to meet the higher mineral requirements of broodmares and foals, resulting in nutritional gaps that may contribute to developmental issues, such as Osteochondritis Dissecans (OCD).
Many pastures have unbalanced mineral profiles—particularly low levels of calcium, phosphorus, copper, and zinc—and improper calcium-to-phosphorus ratios, all of which can negatively affect bone health and proper development in young horses.
Tall Fescue
Tall fescue is a common grass species found throughout much of the southeastern United States.
Many tall fescue plants are infected with an endophytic fungus called Neotyphodium coenophialum, which produces ergot alkaloids. These compounds can potentially pose a serious risk to pregnant mares grazing on this grass.
Mares consuming endophyte-infected tall fescue during the final 30 to 60 days of pregnancy may experience prolonged gestation, dystocia (difficulty during foaling), reduced or absent milk production, and weak or stillborn foals.
However, not all tall fescue is infected. Some varieties are endophyte-free or contain a novel endophyte that does not produce harmful ergot alkaloids. The only way to determine if your tall fescue is toxic is through testing. If testing isn’t possible, it’s recommended to remove pregnant mares from tall fescue pastures at least 60 to 90 days before their expected foaling date.
Choosing the Best Feed for Pregnant Mares
The first step in selecting the optimal feed for pregnant mares is to assess the entire diet, including both forage and horse feed, to ensure a proper nutritional balance. Depending on the forage the pregnant mare receives and the mare's specific health requirements, a full-intake horse feed, a ration balancer, or a combination of the two can be chosen based on the forage fed.
Tribute’s Essential K® and Growth are formulated for broodmares fed primarily grass hay. Growth is also available in various forms, including pellets, textured, and cubed, depending on the pregnant mare's preference and specific needs.
In contrast, Alfa Essentials and Alfa Growth are better suited for pregnant mares whose hay consists of more than 50% legumes.
Work with the Tribute® team to create a free, personalized feeding plan to help ensure your mare’s diet is balance and receive support for managing challenges with broodmares during the breeding season, throughout pregnancy, and while raising foals.
References:
https://www.sciencedirect.com/topics/veterinary-science-and-veterinary-medicine/osteochondrosis
https://bmcvetres.biomedcentral.com/articles/10.1186/s12917-024-04252-z
https://pmc.ncbi.nlm.nih.gov/articles/PMC11394450/
https://ufdc.ufl.edu/UFE0045489/00001
