Supplementing Your Broodmare and Foal

When thinking about the nutrition of broodmares and foals, most people understand the importance of the macro minerals calcium, phosphorus, and magnesium, which is needed for the rapid bone growth in the fetus in late gestation and once the foal is born. However, breeders sometimes don’t realize that certain trace minerals and vitamins during gestation and nursing are extremely important in the growth, development, and health of foals. For this reason it is very important that they supplement their broodmares with a great supplement, like Horse Guard. Without a proper trace mineral and vitamin supplementation her foal could have multiple issues that could have easily been avoided.

Copper, zinc, manganese, and iron are trace minerals in which your pregnant mare must receive adequate amounts during pregnancy in order for the fetal liver to have adequate storage at birth. These four mineral stores are then used by the foal during the first few months of life because the mare’s milk is too low to meet the foal’s requirements, even in a mare that has never been deficient.

Minerals Foals Must Store During During A Mare’s Pregnancy


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Copper is an integral mineral for formation and maturation of cartilage. Research has shown that mares supplemented with copper in the last trimester have foals with less soundness issues than foals born to mares that received no copper supplementation. Feeding supplemental copper to foals from mares that didn’t receive supplementation during pregnancy did not correct the problems. This shows the importance of supplementation of copper during pregnancy rather than providing supplementation to the foal after birth. Furthermore, foals that don’t have adequate stores of copper at birth and/or don’t receive adequate amounts during their first two years are thought to be at a higher risk of developmental orthopedic disease.


Zinc plays an important role in immune function, epithelial tissues, and bone, cartilage, and hoof development. Like copper, zinc needs to be stored in the fetus’s liver during pregnancy as the mare transfers very little through milk. Zinc-deficient foals have decreased antibody levels, which reduce immune function. The effects of zinc deficiency on bone and cartilage formation in foals cause reduced growth rates. In addition, both zinc deficiency and toxicity, has been associated with lesions on the lower extremities related to developmental orthopedic disease. This helps to further drive home the importance of feeding a properly balanced vitamin-mineral supplement, like Horse Guard.


Manganese has many important functions in the body including metabolism, and serving as an antioxidant. In broodmares a manganese deficiency can cause re-absorption of an embryo, making it hard to get the mare bred. Manganese aids in the metabolism of carbohydrates and fats, and serves as an antioxidant in the body. It also aids in cartilage formation, with research suggesting that Manganese deficiency is linked to limb abnormalities in foals. Supplementing with a product that contains Manganese during a mare’s pregnancy will help ensure the foal is able to have strong bones and healthy cartilage during a period that they are growing rapidly.


The transport of oxygen throughout blood and into muscles is reliant on Iron. Iron makes up hemoglobin, the transport molecule of oxygen in the blood. It also makes up myoglobin, which aids in the muscles receiving oxygen. Inadequate levels of iron results in anemia. Foals are more susceptible to iron deficiency than all other classes of horses. In order for foals to have adequate iron levels in the first few months of life iron must be stored in the fetal liver during the mare’s pregnancy.

Other Important Minerals for Mares and Foals


Selenium’s major roles in the body include reproduction, growth, and immunity. Selenium serves as an antioxidant in the body, removing free radicals that damage tissues. It is also crucial in thyroid hormone production to convert the prohormone, triiodothyronine, to the active form, thyroxine. Mares that are selenium-deficient are harder to get bred and if become pregnant are at greater risk of aborting. After foaling selenium-deficient mares also have a greater chance of retaining a placenta.

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A foal born to a selenium-deficient mare is at much greater risk of White Muscle Disease, of which signs include; weakness, trouble standing, difficulty in suckling and swallowing, respiratory distress, and impaired cardiac function. In addition, a selenium deficient foal’s immune system is compromised. Foals from mares that receive 3 mg of organic selenium during pregnancy had greater antibody levels and blood selenium levels and mares had higher selenium levels in colostrum and milk than mares fed 3 mg of inorganic selenium and 1 mg of organic selenium. When mares are supplemented with 3 mg of organic selenium foals are less likely to have contracted tendons and angular limb deformities as well. Foals rely mostly on their mother’s milk to meet their selenium requirement during the few months of life, so adequate selenium supplementation levels during pregnancy and nursing are crucial.


Iodine is essential for reproduction, growth, feed utilization and temperature regulation. In order for thyroid hormones thyroxine and triiodothyronine to be produced iodine must be present to be incorporated into the hormone. An iodine-deficient mare may have a foal with goiters because the thyroid gland becomes enlarged to try and compensate to produce adequate levels of thyroxine. Signs of selenium deficiency in a foal include; stillborn foals or weak foals that can’t stand and nurse, rough hair coat, contracted tendons, limb deformities, and abnormal bone development. Like selenium, foals rely on their mother’s milk to meet their iodine requirements during nursing.

Crucial Vitamins for Mares and Foals

Vitamin A

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Vitamin A is instrumental in reproduction, differentiation of epithelial cells, immune function, embryogenesis, and growth. Hay contains almost no vitamin A because of the oxidation that occurs during curing and storage. Therefore, mares need to be supplemented with vitamin A. Depletion of vitamin A reserves in pregnant mares was found within two months of a diet of hay and vitamin A-free concentrate. Feeding a supplement, like Horse Guard, that contains Vitamin A will help ensure the safety of the pregnancy and the foal. Foals from mares that were vitamin A deficient had lower growth rates for the first 12 months of their life than mares supplemented with vitamin A throughout pregnancy. Both vitamin A deficiency and toxicity negatively affect growth, body weight, and rate of gain in young horses, as reflected by impaired cell proliferation and differentiation. Bones in foals that are vitamin A deficient are shorter and thicker than foals with adequate vitamin A levels because vitamin A affects bone remodeling. It is important that the mare receives adequate levels of vitamin during pregnancy and nursing to maintain an adequate vitamin A status in the foal.

Vitamin E

Vitamin E aids in immune function, nerve and muscle function, growth, and cell membrane integrity.  Mares should be supplemented with a product like Horse Guard that contains vitamin E throughout pregnancy to ensure colostrum and milk concentrations are adequate for the foal at birth. Supplementation of vitamin E in the 30 days before foaling has shown to increase the passive transfer of antibodies to the foal through increased colostrum antibody IgG and IgM levels. Vitamin E is also especially important during the last few months of gestation as tissue rapidly synthesizes in the foal and forming cardiac and skeletal muscles. Stiff, weak muscles can occur from vitamin E deficiency, including the tongue which affects the foal’s ability to nurse. Contracted tendons are also associated with vitamin E deficiency. Vitamin E works synergistically with selenium with immunity and muscle function. It is important that your supplement contains vitamin E and 3 mg of organic selenium for your mares to ensure optimal health of your mare and foal.

Vitamin D

Vitamin D plays a vital role in maintaining blood calcium levels by intestinal calcium uptake, bone mineral release, and resorption of calcium by the kidney. Although not as common of a deficiency, mares that are stalled or that live in northern latitudes, such as the north one third of the United States and Canada are at the highest risk of vitamin D deficiency. A foal that isn’t receiving adequate amounts of vitamin D will in turn have more brittle bones. Vitamin D has also shown to affect appetite, growth, and muscle function. Feeding a supplementation vitamin D during pregnancy will help to ensure a healthy foal is foals with a healthy immune system and strong bones.

Putting it all Together

A proper balance of all vitamins and minerals is very important for the overall health of your mare and foal. While calcium and phosphorus are commonly understood to be crucial during pregnancy, it is important to be aware of the micro minerals and vitamins that are key to health as well. Supplementing your mare with a great vitamin-mineral supplement will ensure that micro minerals requirements of your mare and foal are being met during pregnancy and while nursing. Once the foal is weaned, start them on their own vitamin-mineral supplement. Horse Guard, Super Weight Gain, Mega-Dose, and Trifecta all contains a great vitamin-mineral package for your mare and foal, and allow you to cater the best supplement to your mare’s individual needs. When putting a lot of time, effort, and money into breeding these beautiful horses give them the best chance to grow up strong and healthy by providing them the best nutrition possible. Horse Guard products will help ensure a happy, healthy, high-performance horse.

About Dr. Kelsey J. Nonella Ph.D., P.A.S.

Kelsey J. Nonella, Ph.D. is an equine nutritionist who was riding horses before she could walk. Her love for horses drives her to help educate people on what their horses’ needs in order to have happy, healthy horses. Kelsey went to Cal Poly receiving a Bachelor’s of Science in Animal Science and then onto West Texas A&M, where she got her Masters and eventually her Doctorates in Equine Science. At A&M, Dr. Nonella did extensive research on Selenium within horses. Click here to view her research. Kelsey’s colleagues have mentioned her as one of the United States equine Selenium experts.
View all posts by Dr. Kelsey J. Nonella Ph.D., P.A.S.

4 Responses to “Supplementing Your Broodmare and Foal”

  1. Sharon Wyatt says:

    Would Flow be a good supplement for yearlings too. If not what do you recommend for them

    • mm Dr. Kelsey J. Nonella Ph.D., P.A.S. says:

      Thank you for the question. Flow will provide your yearling with a good source of omega-3 fatty acids, which an important aspect of nutrition in all horses. However, it Flow doesn’t contain a vitamin-mineral supplement to ensure that all of their vitamin and mineral needs are being met during this important time of growth. Therefore, I would recommend Horse Guard as a base supplement, and then you can add the Flow.

      Let me know if I can answer anymore questions.

  2. Shine N Show says:

    Do you have any suggestions for the PSSM horses?

    • mm Dr. Kelsey J. Nonella Ph.D., P.A.S. says:

      Thank you for the question. Selenium and Vitamin E are important to aid in muscle and nerve function in PSSM horses, So, I would recommend Vitamin E and Organic Selenium which contains 5000 IU of Vitamin E and 3 mg of Organic Selenium. You could also add Flaxen Flow. Clinical signs of muscle dysfunction have shown to diminish with small amounts of oil(as little as a 1/4 cup) in horses with persistent signs even when fed low NSC diets. In addition, the omega-3 fatty acids from the 100% flaxseed oil can help with inflammation.

      Let me know if I can answer any more questions for you.

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