When horses start coughing: dust, forage and omega-3
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When horses start coughing, it is easy to assume it is just the dust, particularly when the cough is occasional and the horse seems well otherwise. But mild airway inflammation can affect horses that look completely normal standing in the stable, and sometimes a cough or an unexplained drop in performance is the only sign of it.
A cough that keeps coming back should be discussed with your vet. Alongside that, it is worth looking at whether the diet is supplying the fats the horse uses to control inflammation.
New to omega-3? Read our guide to omega-3 for horses →
What is happening in the airways
Every breath carries tiny particles into the horse's lungs, mostly dust and mould spores coming off forage and bedding.
Inflammation is the horse's normal reaction to them. Immune cells arrive and the airway clears what has been breathed in, and once that job is done the reaction is supposed to switch off again.
Switching off is not passive. The body has to actively produce signalling molecules that stop more immune cells arriving and let the tissue settle. When that does not happen, or when the horse keeps breathing in the same particles, the airway stays irritated, producing more mucus and narrowing as it does.
Why doesn't dust affect every horse?
In the horses that cough, the reaction is out of proportion to what they have actually breathed in. Their immune system treats ordinary forage dust as more of a threat than it is, and the response that follows is bigger than it needs to be and slower to switch off again. That is why taking the dust away helps but does not always settle the horse completely. The exposure has changed, but the way the horse reacts to it has not.
Where EPA and DHA come in
EPA and DHA are the two long-chain forms of omega-3. When a horse takes them in, they are stored in the walls of its cells, including the immune cells lining the airway, and the horse draws on them from there.
Those stores are what the body builds its inflammatory signals from, and what it uses to make the molecules that bring inflammation to a close, called resolvins and protectins. Having enough of them means the horse can produce the signal that starts the reaction and the one that ends it.
Breathing is one of the areas where this has been tested in horses.
The stabled horse
A horse that spends more time in and less time out is often breathing more dust at exactly the point its omega-3 intake drops.
Fresh grass is where a horse naturally gets omega-3, in a short-chain form called ALA, and most of that is lost when grass is cut and dried into hay. So a horse coming in for the winter onto conserved forage faces more challenge to its airways while getting less omega-3 in its diet.
What the breathing supplement study found
Researchers took horses with diagnosed airway disease and moved all of them onto a complete pelleted feed with no hay, which cut their dust exposure sharply. They were then split into three groups for two months: one on a placebo, one on a supplement made from DHA-rich algae, and one on double that dose.
Every group improved, which matters. Taking the hay away helped on its own. But the supplemented horses improved further, and the double dose did no better than the single one.
| Measure | DHA supplement and low-dust diet | Placebo and low-dust diet |
|---|---|---|
| Cough score | improved by 60% | improved by 33% |
| Respiratory effort | decreased by 48% | decreased by 27% |
| Airway neutrophils | fell from 23% to 9% | rose from 11% to 17% |
Neutrophils are the immune cells that gather in an inflamed airway. In the horses getting DHA they more than halved, and in the horses on the placebo they went up.
The air comes first
The supplement was tested on top of a low-dust diet, and the researchers said plainly that continued dust exposure would probably reduce any benefit.
So for a coughing horse the forage and the ventilation come first. Soaking or steaming hay and improving the airflow are what actually change what the horse is breathing, and more turnout helps too. Omega-3 sits alongside that and alongside your vet's advice.
Choosing a breathing supplement for horses
An omega-3 breathing supplement works through the EPA and DHA it supplies, so the useful figure on the label is how many grams of each the daily serving provides. The horses in the trial received 1.5 g of DHA a day from algae, and a product that declares its DHA per serving lets you compare it directly with that.
Look for EPA and DHA listed separately in grams per day, rather than a volume of oil or a total omega-3 figure that includes ALA. EPA and DHA oxidise on contact with air, so check how the oil is protected once the bottle is open.
Does linseed do the same job?
Linseed gives the horse ALA, the short-chain form, which the horse then has to convert into EPA and DHA. That conversion is poor, particularly for DHA, so linseed cannot be assumed to deliver anything like the amount of EPA and DHA used in this study.
Read more about the difference between ALA and EPA/DHA, the conversion step horses depend on, and what happens when a horse is fed DHA.
What Synaxis Core is
Synaxis Core is an omega-3 oil for horses made from algae. A 15 ml daily serving gives 3.0 g of DHA and 1.3 g of EPA already in the long-chain form, ready for the horse to use. The DHA amount sits within the range used in the study and comes from the same kind of source.
See the full ingredients and analysis for Synaxis Core →
How quickly might you see something?
In the study, owners noticed changes in coughing and breathing within the first two weeks, and the level of DHA in the blood peaked at around four weeks.
Airway signs may well be among the first things you notice, and the rest of the horse takes longer. That is why the Synaxis protocol runs for 90 days: long enough to see whether an early change holds, and whether anything slower has shifted as well.
If your horse is coughing or struggling in its work, speak to your vet. Alongside veterinary treatment and managing dust, getting a meaningful amount of EPA and DHA into the diet is worth considering.
Synaxis Core is currently available through the Founding Cohort. Every place runs the full 90-Day Protocol, with outcomes recorded at four and twelve weeks. There are 150 places, and they close once the cohort is full.
To see where your horse's diet stands on omega-3, take the Omega-3 Check.
About the study
The trial was randomised, double-blinded and placebo-controlled. Thirty-five client-owned horses were enrolled and 32 completed it, fourteen with recurrent airway obstruction and eighteen with inflammatory airway disease. The differences between the groups were statistically significant, and lung function improved significantly in the supplemented horses but not in the placebo group.
References
Nogradi N, Couëtil LL, Messick J, Stochelski MA, Burgess JR. 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. Journal of Veterinary Internal Medicine. 2015;29(1):299–306.
Couëtil LL et al. Inflammatory Airway Disease of Horses: Revised Consensus Statement. Journal of Veterinary Internal Medicine. 2016;30(2):503–515.
Duvall MG, Levy BD. DHA- and EPA-derived resolvins, protectins, and maresins in airway inflammation. European Journal of Pharmacology. 2016;785:144–155.