Omega-3 fatty acids are polyunsaturated fats (PUFAs) that are essential in the horse’s diet. Supplementing your horse’s feeding program with omega-3 oil can support anti-inflammatory mechanisms in the body and contribute to overall health and well-being.
The horse cannot synthesize these essential fats on their own, which is why they must obtain them through the diet. Giving your horse a source of omega-3 fats can support a calm demeanor, immune function, and joint health. Omega-3 fats also help prevent dry skin and dull coats and support weight maintenance.
The main healthful omega-3s are EPA (eicosapentaenoic acid) and DHA (docosapentaenoic acid). Horses do not naturally get DHA in their diet.
Instead they convert ALA (alpha linolenic acid) from fresh grasses and forages into DHA and EPA. However, this process is inefficient and does not generate enough of these omega-3s to benefit from their anti-inflammatory properties.
Enriching your horse’s diets with EPA and DHA has numerous beneficial effects. One of the most noticeable benefits is a shiny, healthy coat. These PUFAs also helps prevent skin allergies and dry skin.
Omega-3 supplementation has been shown to prevent tying up in horses that have a history of exertional rhabdomyolysis (ER).
EPA and DHA also support healthy joints and minimize stress responses related to transport. Supplementing with omega-3’s is especially recommended for heavily-worked horses or those in competition.
Dense sources of fat such as omega-3 oils are considered “cool energy” because they are metabolized efficiently without generating much heat. This is particularly beneficial for horses exercising during the hot, humid summer months. 
For horses that are prone to ulcers or hindgut issues, adding omega-3 oil to the diet allows the horse owner to replace some of the grain as a source of calories in the feeding regimen.
This may help reduce the risk of ulcers or dysbiosis related to high-grain intake. Reducing grain intake by adding omega-3s also has a calming effect on horses, improving their focus and handling.
Hard keepers that have difficultly gaining weight could also benefit from essential fatty acids as a dense energy source. This allows you to provide more energy in your horse’s to support healthy weight gain without feeding higher volumes of commercial grains.
Mad Barn’s W-3 oil provides an equine source of omega-3s from plant sources (flax and soybean oil) and microalgae. Microalgae contains high levels of DHA, the main omega-3 in fish oil, but without a fishy smell or taste making it highly palatable for horses.
This supplement also contains Vitamin E which is a potent antioxidant that is best absorbed when consumed along with a fat source and increases the shelf-life of the oil.
This product should be introduced at a rate of 1 ounce (30ml) per day and slowly increased to a maximum dose of 8 ounces (250 ml) per day.
Why Horses Need Omega-3 Fatty Acids
When fatty acids are consumed, they get incorporated into cell membranes in all tissues and organs of the body. Therefore, the composition of fatty acids in the body can have significant effects on how cells function.
Having more polyunsaturated fats like DHA, instead of saturated fats, makes cell membranes more fluid which helps cells respond to outside signals better and stay healthier. DHA can be converted into numerous other molecules in the body that have a wide array of beneficial effects in your equine companion.
Omega-3 vs. Omega-6 Fatty Acids
Omega-3 and omega-6 fatty acids are both polyunsaturated fatty acids that are found in the horse’s diets. They are composed of are long chains of at least 18 carbon atoms in a row connected by chemical bonds.
Many (ie. ‘poly’) of these bonds are unsaturated which means they feature one or more double or triple bonds between the molecules. In contrast, saturated fats have single bonds between their molecules because their bonds are “saturated” with hydrogen molecules.
Specifically omega-3 fatty acids have an unsaturated bond at the 3rd last carbon atom whereas omega-6s have an unsaturated bond at the 6th last position.
The balance of omega-3 to omega-6 fatty acids in the diet is important because omega-3s are converted mostly into anti-inflammatory molecules whereas omega-6s are converted into pro-inflammatory compounds.
Although the optimal ratio has not been worked out in horses, it can be presumed from evidence in other animals and humans, that supplying more omega-3s than omega-6s is beneficial. In other species, the optimal ratio is considered to be between 1:4 and 1:6 of omega-3 to omega-6 fatty acids.
Pasture grasses and forages are high in the omega-3 fatty acid alpha-linolenic acid (ALA). Although total fat content of grass is relatively low at 2-4%, horses that spend a lot of time grazing fresh pasture will consume significant levels of ALA.
Certain plant-based oils are also high in ALA, including flax (linseed), canola, and soybean oil. Grains like oats and barley are typically higher in linoleic acid (LA), an omega-6 fatty acid, which is also high in soybean, canola, corn, sunflower, and safflower oils.
Horses that are constantly grazing on fresh grasses in the natural environment and consuming little grains will not have a high intake of omega-6 fatty acids. Although omega-6s are generally considered bad, the compounds generated from them are important for normal physiological responses and inflammatory events like wound healing.
However, when levels of omega-6s far exceed omega-3s it can put horses at higher risk of inflammatory overreactions, including exaggerated allergic reactions such as heaves and sweet itch. It can also impede recovery from exercise and further exacerbate the metabolic consequences of obesity in easy-keepers or equine metabolic syndrome.
Modern equine nutrition programs with high grain intake often require a correction in the balance of omega-3 to omega-6 fatty acids by adding omega-3s to the diet. This supports a proper balance between pro-inflammatory and anti-inflammatory compounds which helps maintain healthy tissues and organs.
Health Benefits of Omega-3 Fatty Acids for Horses
Below are the top 17 science-backed benefits of omega-3 fatty acids in horses:
Behaviour Benefits and General Health
- Calming effect: Horses fed supplemental fat are reported to be calmer and easier to handle than horses fed a high-starch diet. This coincides with a lower resting heart rate, and decreased reactiveness and misbehaviour. 
- Decreased stress response: Mares that were supplemented with omega-3 fatty acids had lower cortisol levels in response to trailering and stall confinement.
This could make horses easier to manage during transportation and decrease stereotypical behaviours like cribbing that are associated with stall confinement. 
- Coat quality: Horses that have higher levels of omega-3 fatty acids in their blood were found to have a smoother, shinier, and healthier-looking hair coats that appear sleek and glossy.
Omega-3s improve skin barrier function, helping to seal in moisture and protect against irritants that could affect coat and skin condition.Â 
- Skin allergies: Horses that are hypersensitive to Culicoides insects (midges) develop allergic reactions known as sweet itch or Queensland Itch. When given flaxseed, which is high in ALA, susceptible horses had less itchy lesions and reduced inflammation. 
- Improved respiratory function: DHA supplementation on a low-dust diet decreased coughing, improved lung function, and decreased inflammation in the lungs in horses with recurrent airway obstruction (heaves) and inflammatory airway disease. After two months of supplementation, horses given DHA had a 60% decrease in a clinical score of respiratory dysfunction.
Importantly, a similar level of improvement is found when horses are given inhaled corticosteroids and a low-dust diet. Therefore, horses with frequent breathing issues that require corticosteroid treatment might benefit from DHA supplementation.Â 
- Arthritic horses: In arthritic horses, supplementing with EPA and DHA increased stride length and reduced inflammatory markers. Inflammation is a key component of arthritis causing painful joints, decreased performance and reluctance to exercise.
Increasing the ratio of omega-3 (anti-inflammatory) to omega-6 (pro-inflammatory) fatty acids, supports production of numerous compounds in the body that help fight inflammation. 
- Improved joint inflammation: In an experiment that purposely caused inflammation in the joint, providing DHA-rich microalgae decreased the inflammatory response and improved lameness scores. 
- Prevent hindgut acidosis: Horses that are fed high-grain diets are prone to hindgut acidosis due to grain spilling over to the hindgut. Replacing some grain in the diet with omega-3 oils can provide the same or more energy without causing hindgut acidosis.
- Insulin sensitivity: Supplementing horses that have equine metabolic syndrome (EMS) with omega-3 fatty acids has been shown to improve insulin sensitivity. This effect was greatest when marine sources (fish oil and microalgae) were given.
By improving insulin sensitivity, horses with EMS might have less noticeable abnormal fat deposits like cresty neck, and be less prone to laminitis and obesity. 
- Inflammation in EMS: Horses with EMS have chronic low-level inflammation that further decreases insulin sensitivity. DHA-rich microalgae reduced inflammation in horses with EMS. By lessening inflammation, DHA can ultimately improve insulin sensitivity in horses with EMS. 
- Tying up in horses with PSSM: Horses with equine polysaccharide storage myopathy (EPSM, PSSM) have high levels of glycogen in their muscle. This is likely because they are very sensitive to the effects of insulin which results in more sugar being stored as glycogen in the muscle.
These horses are prone to exertional rhabdomyolysis (“tying up”), general muscle stiffness and pain. Providing a low-starch, high-fat diet decreases insulin and sugar levels in the blood which allows the muscle to use more fat for energy which decreases tying up and muscle damage. 
- Improved exercise endurance: Supplementing with fat might cause a “glycogen-sparing” effect. By providing fat as an energy source, the horse is less reliant on using glycogen (a form of sugar storage in liver and muscle) which can be depleted quickly.
This means that fat supplementation could allow the horse to exercise for longer periods of time before tiring.
- Improved tolerance and performance: Horses supplemented with fat in the diet galloped faster and had a steadier heart rate, a sign that they were more fit and tolerant of heavy exercise. 
- Decreased recurrent exertional rhabdomyolysis: In horses that are susceptible to tying up with exercise, adding soy-based fats which are high in omega-3s helped prevent muscle damage, as measured by lower creatine kinase in the blood.Â 
- Increased antioxidant enzymes: Supplementation of oil containing vitamin E and omega-3s to horses in training increased the main antioxidant enzymes glutathione peroxidase and superoxide dismutase.
This could help horses recover quickly from exercise and improve performance. 
- Improved reproductive health: Stallions fed a diet rich in DHA had dramatic improvements in sperm quality. 
- Improved memory and learning in foals: Foals and yearlings whose mares were given DHA during pregnancy were better at learning new tasks including bridling. Even at 2 years old, there were training benefits in young horses if their mares were fed omega-3s during pregnancy. 
Benefits to Exercising Horses
Reproductive Health and Benefits to Young Animals
Feeding Fat to Horses
Horses typically get fat in their diet through grains and commercial concentrates. Although there is no strict recommendation for how much fat to include in the horse’s diet, it is generally suggested that total fat content shouldn’t exceed 8% to minimize interference with fibre digestion and nutrient absorption. This is equivalent to about 2 cups per day for a 500 kg horse.
Providing this mostly as omega-3 fatty acids will help achieve a healthy balance between omega-3 and omega-6 fatty acids and promote an anti-inflammatory state in the body.
Before feeding your horse additional fat, it is recommended to have their diet reviewed by a qualified nutritionist. You can submit your horse’s diet for analysis to determine whether any nutrient levels need to be adjusted.
Types of Fat/Oil Supplements Available
If your primary goal is to help your skinny horse with weight gain, then low-cost vegetable oils that are 100% fat like canola oil or corn oil might be sufficient to provide the added calories needed to achieve a healthy body condition.
However, vegetable oils are high in linoleic acid (LA) an omega-6 fatty acid. Feeding high amounts of vegetable oil might throw off the balance of omega-3 and omega-6 fatty acids. This can contribute to inflammation in the body and its associated negative impacts like insulin resistance and slow recovery from exercise and illness.
A better approach to increasing the energy density of equine diets to achieve weight gain or to provide extra calories without relying on grains is to use ground flax seed and add omega-3 rich oils.
This provides the added benefit of anti-inflammatory effects, improved performance and better mood. Although fish oil is high in DHA, the fishy smell and taste causes palatability issues for picky eaters. Microalgae is just as high in DHA as fish oil but without the fishy smell or taste that can cause poor palatability.
Other commonly used fat supplements are oils from camelina sativa or flax seeds which are members of similar plant families. Both are high in omega-3s and camelina also has higher levels of vitamin E which helps extend its shelf-life.
These oils are high in the precursor omega-3 alpha linolenic acid (ALA) which needs to be converted by the body into DHA and EPA to realize the full omega-3 health benefits. Because horses are inefficient at converting ALA to DHA and EPA, marine sources are preferable and a cost-effective supplement for providing high levels of DHA.
- Kronfeld, DS. Dietary fat affects heat production and other variables of equine performance, under hot and humid conditions. Equine Vet J Suppl. 1996.
- McKenzie, Erica C. et al. Effect of Dietary Starch, Fat, and Bicarbonate Content on Exercise Responses and Serum Creatine Kinase Activity in Equine Recurrent Exertional Rhabdomyolysis. J Vet Intern Med. 2003.
- King, SS. et al. The Effect of Omega-3 Fatty Acid Supplementation on Cortisol and Prolactin Concentrations in Response to Common Stressors in Horses. J Equine Vet Sci. 2009.
- Goh, YM. et al. Plasma n-3 and n-6 fatty acid profiles and their correlations to hair coat scores in horses kept under Malaysian conditions. J Vet Malaysia. 2004.
- Oâ€™Neill, Wendy et al. Flaxseed (Linum usitatissimum) supplementation associated with reduced skin test lesional area in horses with Culicoides hypersensitivity. Can J Vet Res. 2002.
- Nogradi, N. et al. Omega-3 Fatty Acid Supplementation Provides an Additional Benefit to a Low-Dust Diet in the Management of Horses with Chronic Lower Airway Inflammatory Disease. J Vet Intern Med. 2015.
- Hess, T. and Ross-Jones, T. Omega-3 fatty acid supplementation in horses. R Bras Zootec. 2014.
- Brennan, KM. et al. The effect of dietary microalgae on American Association of Equine Practitioners lameness scores and whole blood cytokine gene expression following a lipopolysaccharide challenge in mature horses. J Anim Sci. 2017.
- Hess, T. et al. Effects of n-3 Fatty Acid Supplementation on Insulin Sensitivity in Horses. J Equine Vet Sci. 2013.
- Elzinga, SE et al. Effects of Docosahexaenoic Acidâ€“Rich Microalgae Supplementation on Metabolic and Inflammatory Parameters in Horses With Equine Metabolic Syndrome. J Equine Vet Sci. 2019.
- Ribeiro, WP. et al. The Effect of Varying Dietary Starch and Fat Content on Serum Creatine Kinase Activity and Substrate Availability in Equine Polysaccharide Storage Myopathy. J Vet Intern Med. 2004.
- Oldham, SL. et al. Storage and mobilization of muscle glycogen in exercising horses fed a fat-supplemented diet. J Equine Vet Sci. 1990.
- Melo, S et al. Oil Supplementation Produces an Increase in Antioxidant Biomarkers in Four Beat Gaited Horses. Nutrition. 2014.
- Brinsko, SP. et al. Effect of feeding a DHA-enriched nutriceutical on the quality of fresh, cooled and frozen stallion semen. Theriogenology. 2004.
- Adkin, AM. et al. Maternal fatty acid supplementation influences memory and learning ability in yearling and 2-year-old horses. J Equine Vet Sci. 2015.