Spirulina for Horses with HeavesSpirulina is a nutritionally dense blue-green algae that is used as an equine supplement to support horses with immune or respiratory needs.

Spirulina refers to dried algae, or cyanobacteria, that is harvested from lakes in Africa, Mexico and China. Fed in the form of a concentrated green powder, it is a rich source of bioactive proteins, fatty acids, vitamins, and minerals.

Spirulina powder consists mainly of the cyanobacteria Arthrospira platensis and Arthrospira maxima. The active ingredients include unique antioxidant proteins and anti-inflammatory fatty acids.

This equine superfood is also rich in beta-carotene (the precursor for vitamin A), vitamin C, and vitamin E which are powerful antioxidants that protect all cells of the body.

Spirulina supplementation is used to support respiratory function and metabolic health in horses because of its potent antioxidant, anti-inflammatory and antihistamine properties. This supplement is an excellent protein source that can be used for heavily exercised or growing horses.

It is considered a complete protein because it supplies all essential amino acids which are required in the equine diet. Essential amino acids are those protein molecules that horses cannot synthesize on their own and must obtain from the diet.

Spirulina has been shown to promote weight loss and improve metabolic health in horses with equine metabolic syndrome (EMS). Horses with EMS have smaller cresty necks after being supplemented with spirulina. [2]

It is recommended for horses that are susceptible to recurrent breathing issues like allergies, heaves, and inflammatory airway disease.

Compounds found in Spirulina influence the immune system to moderate the inflammatory response to potential allergens, which helps minimize coughing and headshaking in horses with respiratory allergies. [1]

Spirulina is Generally Recognized as Safe by the US Food and Drug Administration (FDA). It grows best in lakes with very high pH which is not a favourable environment for many other microbes, therefore there is low risk of contamination with other microorganisms.

Mad Barn’s bulk Spirulina powder is composed of pure, dried spirulina without any additional ingredients. The typical feeding rate for a 500 kg horse is 20 grams two times per day.


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  • Supports immune function
  • Used in horses with allergies
  • Supports metabolic health
  • Rich in vitamins & protein

Benefits of Spirulina in Horses

Horse owners feed spirulina supplements to their equine companions for a number of different reasons. It is an excellent source of a wide range of nutrients and active natural compounds with health-promoting effects.

Below is our list of the top 9 benefits of using Spirulina in horses:

1) Supports respiratory function

Spirulina helps support respiratory function in horses that have recurrent issues seasonal or management-related respiratory issues.

These issues are particularly prevalent during the spring and summer when respiratory allergens are abundant in the environment. Horses showed less symptoms like coughing, sneezing and headshaking after they were supplemented with spirulina and jiaogulan. [1]

2) Improves exercise performance

Spirulina improved exercise performance in horses with recurrent respiratory issues. Combining 20 grams of Spirulina with 2000 mg of Jiaogulan twice per day, normalized respiratory recovery following moderate exercise and improved race times.

These horses showed better alertness and higher energy levels with more enthusiasm for work. [1]

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3) Safer alternative for competition horses

For horses in competition, spirulina may be an effective alternative to clenbuterol or corticosteroids to support respiratory function and exercise recovery.

Clenbuterol – a bronchodilator, and anti-inflammatory corticosteroids like dexamethasone are commonly used in horses with recurrent respiratory issues, but are banned for horses in competition.

In a warmblood event horse that was poorly responsive to clenbuterol or corticosteroids, a combination of 2000 mg jiaogulan and 20 grams of Spirulina, given twice daily improved respiratory recovery and decreased coughing. [1]

4) Decreases itchiness due to allergens

Spirulina could decrease seasonal itchiness related to hypersensitivity to airborne particles like dust and pollen allergies.

Spirulina inhibits the release of histamine from mast cells which is one of the main factors that causes itchiness during allergic reactions. [1]

5) Minimizes allergic over-reactions

Spirulina can protect against the development of allergic reactions. Phycocyanin is a selenium-rich protein that is responsible for the blue pigment of spirulina.

Phycocyanin increases production of protective antibodies (IgA and IgG) and decreases production of pro-inflammatory antibodies (immunoglobulin E, IgE). This can help minimize over-reactions to common allergens like dust and pollen. [3]

6) Protects against hives or sweet itch

Anecdotally, spirulina is said to support healthy skin in horses that are prone to skin conditions like hives or sweet itch due to hypersensitivity to insect bites, particularly from midges (Culicoides).

Adding spirulina particularly during the summer months could help reduce skin allergies and infections that might arise from persistent scratching. [1]

7) Supports weight loss with EMS

Spirulina supports weight loss in horses with equine metabolic syndrome. It has been shown to improve metabolic health in horses affected by insulin resistance.

Horses treated with this supplement had diminished cresty neck scores, lower fasting insulin levels and improved glucose tolerance. Improving insulin sensitivity can help prevent horses from developing laminitis (inflammation in the hoof) and chronic lameness. [2]

8) Supplies antioxidant to support healthy tissues

Spirulina is high in antioxidants including the vitamin A precursor beta-carotene, vitamin E, and selenium.

Free radicals that are produced normally during metabolism cause damage to DNA and fats in the cells. Antioxidants neutralize free radicals before they cause damage which keeps cells and tissues healthy and supports their optimal function.

Horses that are slow to recover from exercise or illness might benefit from spirulina to improve their antioxidant status. [2]

Spirulina Powder for Horses

Which Horses Should Use Spirulina?

Horses with respiratory issues like heaves and frequent allergic reactions might benefit from adding Spirulina to their feeding program. Look out for the following signs of respiratory dysfunction, which may be more obvious during exercise or while eating hay:

  • Constant coughing
  • Headshaking, sneezing, nasal discharge
  • Laboured breathing during exhale
  • Wheezing
  • Decrease in exercise performance
  • Slow respiratory recovery after exercise

Tips to Alleviate Respiratory Difficulties in Horses:

Horses that are susceptible to breathing issues, particularly when stall-housed or feeding on hay, are probably reacting to dust, mold or pollen in the hay or bedding.

This is likely the case if symptoms lessen when horses are on pasture and given low-dust or dust-free hay, pelleted feed, or hay cubes. Soaking hay for a few minutes before feeding will help eliminate dust. Bucket feeds should also be wetted down.

Wood chips and shavings can also be a source of dust that cause breathing issues. You may want to consider substituting wood chips or shavings for straw that typically has inhalable particles.

Veterinarians might recommend steroid treatment for horses with chronic respiratory issues. However, long-term treatment with steroids can suppress the immune system and could exacerbate insulin resistance in equine metabolic syndrome or Cushing’s disease, thereby increasing the risk of laminitis. Horses with those conditions might benefit from spirulina to support respiratory function.

Beta-2 agonists like clenbuterol can be effective in the short-term to help horses with acute breathing difficulties but horses often stop responding to this treatment if given long-term. Heavily-exercised horses or those in competition that require respiratory support might benefit from spirulina before and during training and competition to decrease dependence on clenbuterol.

Spirulina for Seasonal Insect Bite Hypersensitivity:

Horses with seasonal hypersensitivity to Culicoides, ticks or mosquitos, might also benefit from Spirulina. Signs of this include: [4]

  • Intense itching causing the horse to rub affected areas including the tailbase, rump or neck. This can lead to hair loss, open sores or raw skin that is susceptible to infections
  • Swollen, oozing or crusty skin along the midline of the belly or rump
  • Swollen sheath in geldings

Spirulina for Equine Metabolic Syndrome:

Horses with equine metabolic syndrome or insulin resistance have shown improvement in metabolic health with spirulina. Signs of EMS include:

  • Unusual fat deposits on the neck (cresty neck), tail head and loin, around the udder or prepuce and above the eyes
  • Easy weight gain
  • Laminitis – showing reluctance to turn, a shortened stride or stiff gait, reluctance to exercise, shifting weight from foot to foot, hooves that are hot to the touch, change in temperament

Additional Reasons to Use Spirulina:

There are other reasons to consider adding Spirulina to your horse’s diet.

In horses with higher protein needs like lactating mares, heavily exercised horses, and young animals, spirulina could be given to support increased protein demand for milk production, exercise recovery, and muscle growth.

Horses fed mostly hay-based diets may be deficient in several vitamins and could benefit from the abundant vitamins and minerals found in this blue-green algae.

Low energy, poor coat, skin or hoof condition might be signs of protein deficiency, inflammatory states or poor antioxidant status.

How to Use Spirulina in Horses

The recommended dose of bulk spirulina powder for a 500kg horse is 20 grams twice per day. This dose can be safely given to horses with EMS and/or respiratory issues, but consult with your veterinarian first to make sure it is appropriate for your horse’s needs.

To minimize avoidance, it is recommended to increase the feeding rate slowly up to 40 grams per day. For picky eaters, spirulina can be combined with oil in a syringe to orally dose the horse. It can also be given along with Mad Barn’s W-3 Oil essential fatty acid supplement to mask the smell for picky eaters.

According to Dr. Kellon, if seasonal allergies are a concern, you may want to begin adding spirulina to the horse’s diet about 4-6 weeks before allergies start. [5]

Once benefits are observed and allergens are no longer present, the serving size can be decreased to 10 grams twice per day as a maintenance dose. Continue to monitor for symptoms. If they re-appear then increase the dose back to 20 grams twice per day.

Spirulina can be safely combined with MSM, flaxseed meal, jiaogulan and vitamin C for additional anti-inflammatory and antioxidant benefits. For horses with sweet itch, the combination of spirulina, ground flax (6-8 oz per day) and chondroitin sulphate (5000mg twice per day) helps support healthy skin.

It is important not to confuse Spirulina with other types of blue-green algae products. There are several other forms of blue-green algae available as equine supplements, however these may differ from spirulina in their nutritional composition and safety.

For example, algae of the species A. flos aquae has been linked to a case of toxicity leading to euthanasia in a horse. [10] This was due to high levels of microcystin – a toxin produced in higher levels by A. flos aquae. Due to lower levels of microcystin in spirulina, toxicity is unlikely to occur with supplementation. [11]

You should always consult a qualified nutritionist before altering your feed program. Submit your horse’s diet for analysis online and one of our equine nutritionists will be happy to provide a complementary review .

Spirulina Research in Horses

Respiratory Function

There are currently no placebo-controlled studies available to evaluate the effects of spirulina on respiratory function in horses. Dr. Eleanor Kellon, a respected veterinarian from the ECIR group, reported on case studies at the European Equine Health and Nutrition Congress in 2006.

She described two horses that were given Jiaogulan (Gynostemma pentaphyllum) and Spirulina Platensis to help with respiratory issues. [1]

In one case, an 8-year-old Warmblood event horse was fed 2000 mg Jiaogulan and 20 grams of Spirulina twice daily. After just two days her respiratory recovery after exercise became normal. The chronic cough she experienced during exercise stopped within a week.

The mare continued to be symptom-free when she was re-evaluated after 6 months of daily jiaogulan and spirulina use.

Another case involved a 4-year-old Standardbred gelding with inflammatory airway disease diagnosed by bronchoalveolar lavage showing high numbers of inflammatory mast cells.

This horse had declining performance at the end of races and poor respiratory recovery which was improved by clenbuterol. Seasonal allergies were also evident by headshaking, snorting and sneezing beginning in early April along with occasional coughing.

Feeding 1000 mg Jiaogulan and 10 grams Spirulina twice per day only partly resolved these symptoms. When the dose was increased to 2000 mg Jiaogulan and 20 grams Spirulina twice per day the headshaking and sneezing stopped, and respiratory recovery rates normalized.

After adding these supplements to his feeding program, the gelding had stronger last quarters in races and improved his speed by one second.

Equine Metabolic Syndrome

A study by Nawrocka et al., published in 2017 examined the effect of Spirulina platensis in horses with EMS. Six horses with EMS were given pelleted spirulina (500g per day) while another six horses with EMS were given pelleted hay. A separate control group of six healthy horses who did not have EMS were also given pelleted hay. [2]

Weight loss

After 3 months of spirulina, horses with EMS had significant weight loss and improvement in body condition score. On average, the EMS horses given spirulina lost 57 kg (125 lbs) after three months and their body condition score improved from 8.3 out of 9 to 7.5 out of 9. In comparison, the EMS horses had no change in body weight or condition score over this time frame.

Importantly, the EMS horses given spirulina had improved markers of metabolic health. Fasting insulin decreased from 84 mU/ml to 62 mU/ml. This is a significant decline, but still much higher than healthy horses whose fasting insulin levels average 3.8 mU/ml.

Insulin sensitivity

A better indicator of metabolic health is the combined glucose insulin test (CGIT) which is considered the most sensitive test of insulin dysregulation in horses. All EMS horses had a positive test result before beginning spirulina treatment, compared to healthy horses that tested negative.

After 3 months, 5 out of 6 EMS horses given spirulina had a negative test result. Specifically, those 5 horses had an average test result of 74.6 mg/dL after treatment, matching the test result of healthy horses (74.0 mg/dl).

This shows that Spirulina helped the majority of horses with EMS respond normally to insulin. This improvement in insulin sensitivity can be seen by a decrease in the cresty neck score from 4.0 to 3.2 in EMS horses given spirulina.

In this study, the researchers also took fat tissue from the tail head of horses with EMS and from healthy horses. Cells from this tissue were grown on petri dishes either with or without Spirulina platensis.

Cells exposed to spirulina grew better in culture and were less likely to die. The researchers attributed this to decreased oxidative stress and improved mitochondrial function.

This suggests that the improvement in insulin sensitivity in EMS horses treated with spirulina was due, at least in part, to healthier fat tissue with better antioxidant status, which is known to improve insulin sensitivity.

Although spirulina is considered high in iron (28 mg iron for 100g of spirulina), giving horses 40 grams per day of spirulina would supply just 11 mg of iron. The iron requirement for a 500kg horse is 400 mg per day and the upper tolerable limit is 5000 mg per day.

Spirulina supplementation was beneficial for horses with EMS despite the high iron levels which are typically associated with poor insulin sensitivity. If you suspect your horse has a high iron intake, spirulina can still be used but it is recommended to balance the iron, zinc, and copper levels to lower the risk of secondary deficiencies.

Active Ingredients in Spirulina

Spirulina is a nutritionally dense supplement that is easily digested. It is especially high in protein (up to 70%). It is considered a complete protein that supplies all the essential amino acids which must be included in the diet because they cannot be made by the horse’s body.

Although it provides all essential amino acids, it is considered low in lysine and methionine. Submit your horse’s diet online for a complementary analysis of your horse’s protein and amino acid needs.

Spirulina is an excellent source of vitamins and minerals to support overall health and well-being of horses. It is especially high in the vitamin A precursor beta-carotene, vitamin C, and vitamin E which are important antioxidants that neutralize free radicals in all cells of the body.

Spirulina is high in vitamin B1, also known as thiamine. Horses can synthesize some of this water-soluble vitamin in the hindgut but they also get it from fresh green pasture. Thiamine is important for carbohydrate metabolism, helping horses get energy from sugar.

It is also involved in helping the nervous system transmit neural signals. Low levels of thiamine in horses are associated with spooky, nervous, and distracted behaviour. Thiamine supplementation has typically been used to calm nervous horses. [6]

The major active compound of spirulina is phycocyanin, a selenium-rich pigment protein with antioxidant and anti-inflammatory properties. It has been shown to effectively protect lipids (fats) in cells from free radical damage which helps cell membranes stay healthy and respond to signals from outside the cell properly. [7][8]

This cyanobacterial supplement is a source of the fatty acid gamma linolenic acid (GLA). Although this is an omega-6 fatty acid (a category of fatty acids typically thought to be pro-inflammatory), GLA is anti-inflammatory. It has been shown to have numerous health benefits in humans including wound healing and tissue repair and anti-bacterial and anti-viral effects. [9]


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  • Supports immune function
  • Used in horses with allergies
  • Supports metabolic health
  • Rich in vitamins & protein

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  1. Kellon, Eleanor Use of the Herb Gynostemma Pentaphyllum and the Blue-green Algae Spirulina Platensis in Horses. Equine Congress. 2006.
  2. Nawrocka, Daria et al. Spirulina platensis Improves Mitochondrial Function Impaired by Elevated Oxidative Stress in Adipose-Derived Mesenchymal Stromal Cells (ASCs) and Intestinal Epithelial Cells (IECs), and Enhances Insulin Sensitivity in Equine Metabolic Syndrome (EMS) Horses. Marine Drugs. 2017.
  3. Nemoto-Kawamura et al. Phycocyanin enhances secretary IgA antibody response and suppresses allergic IgE antibody response in mice immunized with antigen-entrapped biodegradable microparticles. J Nutri Sci Vitaminol. 2004.
  4. van der Rijt, Renske et al. Culicoides species attracted to horses with and without insect hypersensitivity. The Vet J. 2008. View Summary
  5. Kellon, Eleanor. Optimizing the Immune System. Dr. K’s Horses Sense. 2020.
  6. Irvine, CHG et al. The effect of large doses of thiamine on the horse. NZ Vet J. 1962.
  7. Madhava Reddy, C. et al. Selective Inhibition of Cyclooxygenase-2 by C-Phycocyanin, a Biliprotein from Spirulina platensis. Biochem Biophys Res Comm. 2000.
  8. Liu, Qian et al. Medical Application of Spirulina platensis Derived C-Phycocyanin. Evid Based Complement Alternat Med. 2016.
  9. Roughan, Grattan P.Spirulina: A source of dietary gamma-linolenic acid? J Sci Food Agri. 1989.
  10. Mittelman, N.S. et al. Presumptive Iatrogenic Microcystin Associated Liver Failure and Encephalopathy in a Holsteiner Gelding. J Vet Intern Med. 2016. View Summary
  11. Roy-Lachapelle, Audrey et al. Detection of Cyanotoxins in AlgaeDietary Supplements Toxins. 2017.