What you need to know
When it comes to equine nutrition, few supplements have attracted as much interest overseas in recent years as salmon oil. Praised for its rich supply of omega-3 fatty acids, salmon oil has been linked to benefits ranging from joint comfort and skin health to immune resilience and even better metabolic health.
In this article, we take a closer look at what salmon oil offers our horses, unpacking the research, the practicalities of feeding, and the potential limitations.
What we know, what we don’t, and how to use it
Salmon oil is a marine fish oil naturally rich in the long-chain omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). EPA and DHA are the bioactive omega-3s that participate in anti-inflammatory pathways and are incorporated into cell membranes throughout the body. Horses can’t make EPA and DHA efficiently themselves, so they must come from the diet – either from fish (e.g., salmon oil) or from marine microalgae.
Why salmon oil (EPA/DHA) is different from ‘plant omega-3’
Flax, chia and pasture supply alpha-lipoic acid (ALA), a shorter-chain omega-3. In horses, feeding marine sources raises EPA and DHA in blood and tissues far more reliably than ALA alone. In controlled trials, fish/marine oils increased EPA/DHA in plasma, red cells and even skeletal muscle, whereas flax raised mostly ALA. This matters because many of the anti-inflammatory effects of omega-3s are specific to EPA/DHA.
Salmon oil, therefore, offers a direct route to provide EPA/DHA, while plant oils are best seen as complementary fat sources with different profiles.
Where the evidence for the benefits of salmon oil is strongest
1) Respiratory health (inflammatory airways disease/‘equine asthma’/recurrent airway obstruction)
The best clinical data in horses comes from the airways. In a randomised, controlled trial, adding an omega-3 supplement that delivered ~1.5–3 g DHA/day for eight weeks improved cough scores, breathing effort, and airway health beyond the benefit of a low-dust diet alone. Plasma DHA rose within four weeks.
2) Tissue incorporation into joints and lungs
Beyond the blood, EPA/DHA from supplementation are taken up by synovial fluid (joints) and pulmonary surfactant (the ‘lubricant’ of the lungs), potentially improving the body’s capacity to resolve inflammation in those regions. Peak incorporation typically occurs after approximately 60 days of daily feeding. Some studies show changes in inflammatory markers in the joints particularly with high marine omega-3 intake, but clinical endpoints (lameness scores, force plate data) are inconsistent so far. We should expect ‘support’ from salmon oil, rather than it being a stand-alone therapy, but as supplements go, this is pretty interesting!
3) Exercise metabolism (emerging but intriguing)
In exercised horses, fish oil has been associated with a lower heart rate during work and alterations in glucose/insulin responses during and after exercise. These are both signals that fat metabolism may be shifting in a favourable way. It is worth noting, however, that these are performance-physiology markers, not performance guarantees.
4) Insulin and metabolic health (early data)
For horses with equine metabolic syndrome (EMS), a pilot study using DHA-rich microalgae (a plant-based EPA/DHA source) altered circulating fatty acids, lowered triglycerides, and prevented the rise in insulin response seen in unsupplemented controls over 46 days. Results are promising but preliminary, and larger studies are needed, but if the science continues to support this, it could be a real breakthrough for horses suffering from metabolic disease.
5) Skin and coat
Many owners report glossier coats with added oil. Equine trials directly linking EPA/DHA to coat quality are limited; improvements are likely due to a better supply of essential fatty acids and overall calorie density. For skin and coat health, good management and parasitic control still matter most, but oil is a good add-on.
How to add salmon oil safely
Start low and go slow
Introduce any oil gradually over two to three weeks to avoid loose manure and to let the hindgut adapt to the new product. Regular guidance suggests an upper practical limit around 1ml oil per kg body weight per day (≈500 mL/day for a 500kg horse) when fat is used as an energy source, but this is far above typical ‘supplement’ amounts. You won’t need anywhere near this upper limit to achieve the benefits of salmon oil. Follow the guidelines of your chosen manufacturer.
Study-based dosing examples (to anchor expectations, not prescriptions):
- Respiratory disease: Administration of ~1.5–3 g DHA/day for eight weeks, alongside a low-dust diet, improved clinical signs. For a 500kg horse, this is usually achieved with tens of millilitres of a high EPA/DHA oil (check your label for the actual mg per ml).
- Tissue incorporation: Expect meaningful EPA/DHA in plasma and joint/lung compartments by 60–90 days of daily intake.
Because salmon oil products vary widely in concentration, dose to the grams of EPA and DHA, not just ‘tablespoons of oil.’ Read the label and work with your vet or equine nutritionist.
Vitamin E and freshness
Adding polyunsaturated fats increases the diet’s oxidative load. One controlled study found no rise in oxidative stress markers during 90 days of fish- or flax-oil supplementation, but many nutritionists still pair added oils with vitamin E and emphasise fresh, well-stored products to minimise the risk of rancidity. Guidance commonly suggests ~1–1.5 IU vitamin E per ml of added oil when feeding higher oil intakes.
Practical tips
- Split the daily amount of oil over two to three meals to improve acceptance.
- Top-dress the oil on feed or mix with a small mash.
- Introduce oil along with a low-dust management plan if airways are the target (soaked/steamed hay or haylage, good ventilation).
- Monitor weight as oil adds calories. Adjust other concentrates if needed.
Quality, sourcing, and sustainability
- Choose equine-labelled fish oils from reputable manufacturers that disclose EPA and DHA per ml, harvest species, and freshness/oxidation controls.
- Salmon oil is a very good option but other fish oils (anchovy/sardine) and algal oils can deliver similar EPA/DHA.
When salmon oil is worth considering
- Horses with mild-moderate equine asthma/inflammatory airways disease as part of a comprehensive low-dust management programme.
- Older, arthritic horses where multi-modal joint management is already in place; EPA/DHA can be a supportive add-on.
- EMS-prone or overweight horses under veterinary supervision, where diet, weight loss, and exercise are already addressed; omega-3s may help fat profiles and insulin dynamics.
When to be cautious
- Bleeding risk is theoretical at very high fish-oil doses; stick to targeted EPA/DHA amounts and consult your vet before combining with medications that affect clotting.
- Allergies or taste aversion: a few horses dislike marine flavours, but most don’t seem to mind them.
- Don’t expect miracles: Omega-3s are tools, not cures. Prioritise forage quality, dust control, body condition, and training/management fundamentals.
Bottom line
For horses, the most convincing data for salmon oil supplementation sit in respiratory health and documented tissue incorporation of EPA/DHA, with promising but still developing evidence in joint comfort and metabolic support.
Sources
Controlled trials and reviews underpinning the guidance above include O’Connor 2004 & 2007 (exercise metabolism; serum fatty acids); Hess et al. 2012 (tissue incorporation), Nogradi et al. 2015 (airway disease outcomes); Christmann et al. 2021 (synovial/lung incorporation); Elzinga et al. 2019 (EMS pilot); White-Springer et al. 2021 (oxidative stress with oil feeding); and ISU Extension (feeding oil safely).
Balius Salmon Oil