Horse on Optimum Defense label

Supporting the Equine Immune System with Optimum Defense

The equine immune system is a vast, complex biological apparatus. How well it functions depends on a number of factors including nutrition, stress, and age.

Our horses’ immune systems can be challenged further by environmental factors, high-intensity training, or metabolic issues.

The first line of defense

The horse’s defense mechanisms began at the skin, the respiratory system, the digestive tract, and the reproductive, and urinary tracts. When these physical defenses are breached, chemical messengers alert and activate the immune and inflammatory response. We can see this as heat, swelling, pain. Other signs are nasal discharge, change in manure, and infections.

Health begins in the gut.

A large percentage of the horse’s immune system is in the gut. Imbalances in the gut microbiota can allow a proliferation of unfriendly bacteria. This causes an inflammatory response, leading to immune system dysregulation and damage to the intestinal lining.1

The nutrition factor

Specific minerals, amino acids, and vitamins play important roles in the functions of the immune system.

The fat-soluble vitamins A, D, and E support innate immunity, immune system modulation, and production of immune-supportive elements.

The trace minerals copper, zinc, selenium, and iron, provide defense against reactive oxygen species (ROS), support innate and acquired immune systems, immune cell integrity, and growth of cells for immune function. Because forages contain high levels of iron, deficiency of iron is rare in horses.

Omega 3 fatty acids: reduce inflammation and support immune function.


Common Challenges for the Equine Immune System

• Metabolic horses 
Equine Immune System Support with Optimum Defense | BioStarUSOngoing research shows that Cushing’s horses can experience immunosuppressive effects because of the abnormal cortisol release in the body.

Studies in humans show that diabetes and obesity affect immune function. This could also be true in horses, although there is little specific research on this.



• Psychological Stress
Chronic stress either physical or mental can weaken the immune system. High levels of cortisol can suppress the immune system.

Stress is a key factor in many issues horses face. Reducing cortisol by addressing stress factors in the horse’s environment is key to helping the immune system function well.

• Physical stress or hard exercise
When a horse becomes sore from hard exercise, non-steroidal anti-inflammatory drugs (NSAIDS) may impair the immune system’s ability to adapt to more rigorous training.

Horses end up with a lower inflammatory response to vigorous work as the immune system becomes conditioned and the muscles get stronger.

• Aging
Chestnut mare and bay foalThe health of a mare has a direct impact on the development of a foal’s immune system. Mares pass on antibodies to their foals through milk and colostrum, which offers immune support. Therefore, good nutrition, exercise, and low stress levels are important for pregnant mares.

Older horses may experience chronic inflammation, leading to a poorly functioning immune system. Some researchers refer to chronic inflammation in older horses as “inflamm-aging.”

The aging process may cause a gradual deterioration of the immune system. This is known as immunosenescence. This deterioration affects both the innate and acquired immune system.

• Respiratory disease: recurrent airway obstruction and heaves
Heaves is often seen in adult and senior horses, and many veterinarians now classify it as equine asthma. Equine asthma is a chronic inflammatory condition associated with a dysregulated immune response.

As one study pointed out: “As severe equine asthma mainly affects adult and geriatric horses, the contribution of immunosenescence, inflamma-aging, and age-related oxidative stress should not be underestimated.2


• Equine allergies
Common allergic reactions in horses are hives, coughs, nasal discharge, or vigorous itching. These are signs that the horse’s immune system is hyper-sensitized to certain allergens. The immune system overreacts, releasing too many antibodies, histamines, and prostaglandins.

Horses can develop food sensitivities to specific grasses, grains, or feed ingredients. Horses can even have mild to moderate allergic reactions to medications, dewormers, and vaccines.

Supporting the immune system is important for horses with EPM, and for horses that may be exposed to the protozoa that causes it.

It’s estimated that over 50% of horses in the United States have been exposed to Sarcocystis neuroma, the organism that causes Equine Protozoal Myeloencephalitis (EPM). Some horses are able to mount an effective immune response. Other horses can succumb to the effects, and others harbor the protozoa for months or years and develop symptoms later.

• Lyme Disease
Lyme disease is a tick-borne bacterial infection caused by Borrelia burgdorferi. Supporting the immune system is important in managing this chronic disease that can have recurring flare-ups. If your horse is being treated for Lyme disease with antibiotics it is important to support the GI tract as well.

Comprehensive support for the immune system:

Biostar’s Optimum Defense combines bioavailable vitamins, minerals, and plants in our Optimum 2.0 formula, with specific ingredients to help support homeostasis of the immune system.


Spirulina: This blue-green algae can help with seasonal allergies by blocking histamines. It can block the production of inflammatory signaling molecules to support a healthy inflammatory response.3



Bovine colostrum: Provides over 80 different immune factors including Immunoglobulin A, Immunoglobulin G, and Lactoferrin; contains Proline-rich polypeptides that provide immune-regulatory properties. Bovine colostrum is the gold standard in immune support.

Colostrum is graded by the percentage of Immunoglobulin G (IgG) content. Biostar’s colostrum is 38% IgG. The next-higher grade of 45% IgG and higher is for foals who need replacement colostrum.

Bovine colostrum supports immune regulation.4 This is important because a horse that is experiencing an allergic response, does not need the immune system to be further stimulated or activated. Immune regulator foods support the return of the immune system to homeostasis.

Quercetin- Sophora Japonica flowers circlePatented Quercetin extract: Quercetin is considered the “queen of flavonoids.” Flavonoids are important biological compounds found in various fruits, trees, and plants that provide antioxidant and anti-inflammatory properties. This is important because of inflammation’s connection to immune dysfunction. Research has shown that quercetin plays a modulating and regulatory action on inflammation and the immune system as well as gastrointestinal cytoprotective activity, and reduction of histamines.5

Quercetin is found in various foods: apples, citrus fruits, tea, onions, grapes, cherries, raspberries, brassica vegetables, tomatoes, and certain medicinal botanicals such as Ginkgo Biloba, Japanese Pagoda Tree, and Sambucus.

Biostar uses a patented quercetin extract from Italy that is sourced from the flowers of the Japanese Pagoda tree, which also have a long history of use in Traditional Chinese Medicine.

Our Quercetin extract is backed by studies demonstrating this extract to be 20 times more bioavailable than quercetin dihydrate, and able to be effective at lower dosages.

Quercetin powders that are commercially available in supplements can have low bioavailability due to the fact that isolated quercetin (not in its whole food form as in apples or onions) is not water-soluble, reducing bioavailability in the body.

Quercetin has been shown to optimize sports performance and physical recovery. It is very beneficial for horses with allergies and equine asthma as it acts as a histamine inhibitor.6

Read more about Quercetin.

Proprietary, synergistic mushroom extract blend:

Turkey Tail MushroomTurkey Tail: This medicinal mushroom provides potent polysaccharides including polysaccharide K (PSK) and polysaccharide peptide (PSP) to support a healthy immune response and management of the inflammatory response. It is one of the most widely-used medicinal mushrooms for immune system support in Traditional Chinese Medicine (TCM).

Turkey Tail assists with gut regulation of bacteria. It provides Polysaccharide Peptides (PSP) that act as prebiotics.7

Cordyceps mushroomsCordyceps: This medicinal mushroom promotes the adaptive immune system including cellular and humoral immunity.8 Researchers have shown cordyceps can regulate intestinal bacteria by improving gastrointestinal-associated lymphoid tissue and systemic immunity. Cordyceps has demonstrated the ability to improve the dysfunction of the gut barrier.9 This is important as a large proportion of the immune system is in the GI tract.

Astragalus herbAstragalus (Huang Qi): Considered a master immune herb in Traditional Chinese Medicine. It has been prescribed in TCM texts for thousands of years as an important qi tonifier, meaning support for the vital life force. Studies on animals and humans show that Astragalus supports immune system health by improving functions of B and T lymphocyte activity. These immune cells are responsible for defense and fighting infections. Astragalus also provides support for beneficial gut bacteria by reducing pathogenic microflora.10

Astragalus is considered an adaptogen, meaning it’s capable of promoting homeostasis.

Optimum Defense 60 serving bag


Biostar’s Optimum Defense™ combines the health benefits of bioavailable multivitamins and minerals with specific ingredients and plants that target and support a healthy gut and immune system.



Tigger Montague | BioStar USAbout the Author: With over 30 years experience in the equine and human supplement industry, Tigger Montague knows nutrition from the synthetic side as well as the whole food side. She started BioStar US in 2006 with formulas she created in her kitchen. Before she started the company, she was an avid rider and competitor with eventing and show jumping, until she got hooked on dressage in the late 1980’s. She has competed on horses she’s owned and trained all the way from training level to Grand Prix.



    1. Wu, H. J., & Wu, E. (2012). The role of gut microbiota in immune homeostasis and autoimmunity. Gut microbes, 3(1), 4–14.
    2. Bullone, M., & Lavoie, J. P. (2017). The Contribution of Oxidative Stress and Inflamm-Aging in Human and Equine Asthma. International journal of molecular sciences, 18(12), 2612.
    3. Cingi, C., Conk-Dalay, M., Cakli, H. et al. The effects of spirulina on allergic rhinitis. Eur Arch Otorhinolaryngol 265, 1219–1223 (2008).
    4. Struff, W. G., & Sprotte, G. (2008). Bovine colostrum as a biologic in clinical medicine: a review–Part II: clinical studies. International journal of clinical pharmacology and therapeutics, 46(5), 211–225.
    5. Li, Y., Yao, J., Han, C., Yang, J., Chaudhry, M. T., Wang, S., Liu, H., & Yin, Y. (2016). Quercetin, Inflammation and Immunity. Nutrients, 8(3), 167.
    6. Mlcek, J., Jurikova, T., Skrovankova, S., & Sochor, J. (2016). Quercetin and Its Anti-Allergic Immune Response. Molecules (Basel, Switzerland), 21(5), 623.
    7. Hobbs, C. (2004). Medicinal Value of Turkey Tail Fungus Trametes versicolor (L.:Fr.) Pilát (Aphyllophoromycetideae). A Literature Review. International Journal of Medicinal Mushrooms, 6, 195-218.
    8. Lin, B. Q., & Li, S. P. (2011). Cordyceps as an Herbal Drug. In I. Benzie (Eds.) et. al., Herbal Medicine: Biomolecular and Clinical Aspects. (2nd ed.). CRC Press/Taylor & Francis.
    9. Gu, G. S., Ren, J. A., Li, G. W., Yuan, Y. J., Li, N., & Li, J. S. (2015). Cordyceps sinensis preserves intestinal mucosal barrier and may be an adjunct therapy in endotoxin-induced sepsis rat model: a pilot study. International journal of clinical and experimental medicine, 8(5), 7333–7341.
    10. Liu, P., Zhao, H., & Luo, Y. (2017). Anti-Aging Implications of Astragalus Membranaceus (Huangqi): A Well-Known Chinese Tonic. Aging and disease, 8(6), 868–886.
Print Friendly, PDF & Email

You may also like...