Omega-3 for Horses: ALA, EPA & DHA Explained

Omega-3 fatty acids play an important role in equine health, but not all omega-3s are the same.

Omega-3 is a family of fatty acids, and the three that matter most for horses are ALA, EPA and DHA. They come from different sources, are used differently by the body and, importantly, feeding one does not necessarily mean that a horse is receiving meaningful amounts of the others.

Horses naturally consume omega-3 from fresh grass, predominantly in the form of ALA, and linseed and chia are also rich sources of ALA. EPA and DHA are long-chain omega-3 fatty acids, and they originate with microalgae, the organisms at the base of the aquatic food chain that manufacture them in the first place. Fish do not make EPA and DHA; they accumulate them by eating algae, which puts them one step further along the chain than the source itself.^{7 8}

Understanding that distinction makes it much easier to decide whether your horse needs additional omega-3 and which source makes sense.

What omega-3 actually does

Omega-3 is a structural nutrient. It becomes part of the horse, which sets it apart from a joint powder or a calmer.

Every cell in a horse's body is wrapped in a membrane, and those membranes are built largely from fatty acids. What a horse eats therefore ends up as part of its physical structure: the lining of the airways, the surface of joint tissue, the skin beneath the coat, the wall of every red blood cell. The fatty acids available in the diet determine what those membranes are made of.

That matters because a membrane is not simply packaging. It is where a cell receives signals and decides how to respond, so what it is built from influences how the body behaves under load.

The clearest example is inflammation, which has a worse reputation than it deserves. Inflammation is a normal and necessary response, and a horse could not heal without it. Think of a cut: warm, swollen and tender for a few days, then healed. That is inflammation doing its job.

What matters just as much is how it ends. The body actively brings an inflammatory response to a close, and it does that by manufacturing signalling molecules called resolvins. EPA and DHA are the raw material those molecules are made from.⁴

So the reason omega-3 matters to a horse is structural and specific. It is what the body builds membranes from, and it is what the body uses to bring inflammatory processes to an end. Which omega-3 a horse is getting is therefore a different question from whether it is getting any.

What is omega-3?

Omega-3 is a family of polyunsaturated fatty acids rather than a single nutrient. The three forms most relevant to horse owners are these.

Omega-3	Full name	Common sources
ALA	Alpha-linolenic acid	Grass, linseed/flaxseed, chia, sea buckthorn (seed oil)
EPA	Eicosapentaenoic acid	Algae, fish oil
DHA	Docosahexaenoic acid	Algae, fish oil

ALA is an essential fatty acid, meaning the horse cannot manufacture it from scratch and therefore needs to obtain it from the diet.

EPA and DHA can in principle be produced from ALA through a series of conversion steps, but in horses the feeding trials have not been able to demonstrate that this happens to any measurable degree.^{1 2} We look at what those trials found further down this page.

This matters because EPA and DHA are incorporated directly into cell membranes and provide the substrate the body uses to make the signalling molecules involved in bringing inflammatory processes to a close.^{1 4}

Where do horses naturally get omega-3?

For a horse grazing good-quality fresh pasture, grass can provide substantial amounts of ALA.

The situation changes when pasture intake falls. Alpha-linolenic acid is concentrated in the leaf, and the amount present in any given forage depends heavily on how mature the plant was when it was cut. A meta-analysis of forage fatty acid composition found that the stage of growth at harvest was the single biggest influence on the fatty acid content of a forage, and that wilting and drying, particularly under poor drying conditions, altered the fatty acid profile further.⁶

So conserved forage is not a like-for-like replacement for fresh grazing, and the fatty acid profile of a stabled horse's diet can look very different from that of a horse living out on pasture.

Read more: what happens to omega-3 when grass becomes hay →

ALA vs EPA and DHA: what's the difference?

This is one of the most important distinctions in equine omega-3 nutrition.

ALA

ALA is the principal omega-3 found in plants: fresh grass, linseed and linseed oil, chia seed, and sea buckthorn seed oil. All are useful ways of increasing the omega-3 content of a horse's diet, but ALA isn't the same molecule as EPA or DHA.

EPA and DHA

EPA and DHA are longer-chain omega-3 fatty acids, and instead of relying on the horse to manufacture them from ALA, they can be supplied directly in the diet. Once supplied, they are incorporated into cell membranes throughout the body and participate in the pathways involved in inflammatory signalling and its resolution.¹

DHA and EPA are also the raw material for a family of molecules called specialised pro-resolving mediators (resolvins among them), which are what the body uses to bring an inflammatory response to an end. These have been measured in horses, in a trial that assessed plasma omega-3 and pro-resolving mediator concentrations in Thoroughbred racehorses alongside airway cytology.⁴

This is why research increasingly distinguishes between simply increasing dietary omega-3 and specifically providing long-chain EPA and DHA.

Read more: the difference between ALA and EPA/DHA →

Can horses convert ALA into EPA and DHA?

The conversion pathway exists in mammals and is generally assumed to exist in the horse. What the equine feeding trials show is that whether or not the machinery is there, the result does not appear in the blood: horses fed ALA sources show no measurable rise in red blood cell EPA and DHA, even over 90 days and at matched omega-3 intakes.^{1 2}

Read more: the conversion step horses depend on, and why it often falls short →

Is linseed a good source of omega-3 for horses?

Yes. Linseed is an excellent plant source of ALA and a genuinely useful ingredient in equine diets, providing calories, protein and fatty acids as well as raising dietary omega-3 intake.

What linseed does is put back something the diet has lost. A horse on fresh pasture takes in ALA every day it grazes, a horse living on hay takes in considerably less, and linseed restores it. That is a real job and linseed does it well.

What linseed does not do is supply EPA and DHA. Those are the long-chain forms the horse builds into its cell membranes and draws on to bring inflammatory processes to a close, and linseed contains no meaningful quantity of either. It supplies the raw material and leaves the horse to do the converting.

So linseed restores the omega-3 a horse would have taken in from grass. It does not deliver what the long-chain forms do.

Read more: why feeding linseed makes sense for coat, and what it doesn't do →

What are the best sources of omega-3 for horses?

There isn't one universally best source, because different sources provide different fatty acids.

Fresh grass

Fresh pasture is the horse's natural dietary source of omega-3 and provides predominantly ALA. For horses with substantial access to good-quality pasture, it can make a meaningful contribution to dietary omega-3.

Linseed

Linseed is rich in ALA and is one of the most commonly used plant sources of omega-3 in equine diets, but it does not provide significant amounts of EPA or DHA.

Chia seed

Like linseed, chia provides predominantly ALA. It can increase total dietary omega-3 intake but shouldn't be considered equivalent to directly supplying EPA and DHA.

Fish oil

Fish oil provides both EPA and DHA and has historically been used when long-chain omega-3 supplementation is required, though palatability, sustainability and oxidation are all considerations when using fish oils in horses.

Algae oil

Microalgae are where EPA and DHA come from in the first place, as the primary producers of long-chain omega-3 in aquatic ecosystems, and the reason oily fish contain these fatty acids at all is that they eat algae, or eat something that did.^{7 8} Sourcing from algae therefore provides EPA and DHA from the organism that manufactures them, without the fish as intermediary.

Read more: fish oil or algae oil for horses? →

Linseed vs algae omega-3

These aren't necessarily competing ingredients, because they provide different things.

	Linseed	Algae oil
Main omega-3	ALA	EPA and/or DHA
Plant or algal source	Yes	Yes
Provides ALA directly	Yes	Usually little
Provides EPA directly	No meaningful amount	Yes, depending on algae
Provides DHA directly	No meaningful amount	Yes
Requires conversion first	Yes	No
Useful source of calories	Yes	Yes, though fed in much smaller quantities

A horse can therefore receive linseed and a source of EPA and DHA, since they aren't mutually exclusive. The appropriate choice depends on what you're trying to achieve with the diet.

What does the research say about omega-3 supplementation in horses?

Equine studies have investigated omega-3 supplementation across several areas including respiratory health, exercise, inflammatory responses, reproduction and metabolic health.

One important consideration when interpreting these studies is which omega-3 was actually fed, because a study using linseed or another ALA source isn't testing the same nutritional intervention as a study providing EPA and DHA directly. The 90-day mare study is the clearest illustration: two groups received the same quantity of omega-3, and only one of them showed any change in red blood cell EPA and DHA.¹

Studies also vary considerably in dose, duration, population and outcome measures, which makes sweeping claims of the "omega-3 does X" kind problematic.

Omega-3 and respiratory research

One of the more substantial pieces of equine research on long-chain omega-3 looked at horses with chronic lower airway inflammatory disease. In a randomised, controlled clinical trial, horses were fed a low-dust complete pelleted diet and randomly assigned to receive either an algae-derived supplement providing DHA or a placebo, for two months. Plasma DHA rose and peaked at around four weeks, and while every horse in the trial improved because the low-dust diet alone did a great deal, the supplemented group improved more across cough score, respiratory effort and airway cytology.³

The comparison was supplement plus management against management alone, and the authors concluded that the supplement provided an additional benefit to a low-dust diet. The supplement was algae-derived and supplied DHA in the low grams per day, which gives a useful reference point when reading a label because it shows the order of magnitude studied in horses.

A horse with respiratory symptoms needs veterinary investigation and environmental management, and nutrition sits alongside that rather than in place of it.

Read more: when horses start coughing, dust, forage and omega-3 →

Omega-3, exercise and recovery

Exercise naturally produces an inflammatory response, which is part of the normal process through which tissues respond and adapt to work. Because EPA and DHA influence cell-membrane composition and inflammatory signalling, researchers have investigated their role in exercising horses, though the evidence here is thinner than the respiratory work and the outcome measures vary widely between studies, making this an area of active interest rather than a settled finding.

The role of omega-3 here is nutritional: it provides the substrate that the body's own regulatory mechanisms draw on.

Omega-3 and skin health

Fatty acids are structural components of skin and cell membranes, and the fatty acid composition of the diet influences the fatty acid profile of tissues.

Equine work in this area has largely used plant oils supplying ALA rather than direct EPA and DHA, with one recent study feeding camelina, flaxseed and canola oils and measuring skin fatty acid profile and inflammatory responses in healthy horses.⁹ Further research feeding EPA and DHA directly is needed.

Persistent itching, lesions, hives or other skin abnormalities should always be investigated rather than assumed to be nutritional.

Joints, metabolic health and DHA

Read more: omega-3 and horses' joints, what the research has measured →

Read more: omega-3 for metabolic horses →

Read more: DHA for horses, what happens when you feed it →

What is the ideal omega-3 to omega-6 ratio for horses?

You'll often see recommendations for a particular omega-6 to omega-3 ratio, but in practice this is more complicated than it sounds.

Not all omega-3 fatty acids behave identically, and neither do all omega-6 fatty acids. A simple ratio also tells you nothing about the absolute amount of either being consumed, since a diet containing large amounts of both families could have exactly the same ratio as a diet containing very little of either.

For that reason, looking at which fatty acids are actually being supplied can be more informative than pursuing a supposedly perfect ratio.

How much omega-3 does a horse need?

There is no established daily requirement for EPA and DHA in horses. The National Research Council's Nutrient Requirements of Horses sets a recommended daily intake for linoleic acid but publishes no recommendations for ALA, EPA or DHA, because the data to set one does not exist.⁵

So be cautious about any product presenting a particular amount as the definitive correct dose, since research studies have used different doses according to the fatty acid being investigated and the outcome intended.

When comparing products, look beyond the quantity of oil or powder being fed and establish how much of the actual fatty acids the daily serving supplies.

How to choose an omega-3 supplement for your horse

Start with what you are actually trying to provide. If you're looking for a plant source of ALA, linseed or chia may be suitable; if you're specifically looking for long-chain omega-3, check whether the product declares EPA and DHA individually.

Things worth looking for include:

• the type of omega-3 supplied
• grams of EPA per daily serving
• grams of DHA per daily serving
• source of the fatty acids
• recommended daily amount
• how the oil is protected from oxidation
• storage instructions
• whether the manufacturer clearly explains what is actually in the product

Be cautious about comparing products solely according to the amount of "omega-3 oil" they contain, because the concentration and fatty acid profile can differ substantially.

A direct source of EPA and DHA for horses

Synaxis Core was developed to provide horses with EPA and DHA directly from microalgae. Each 15 ml daily serving provides 3.0 g DHA and 1.3 g EPA, which is 4.3 g of EPA and DHA per day, without relying on the conversion of ALA and without using fish oil.

Synaxis Core isn't intended to replace good forage, appropriate veterinary care or the role of ingredients such as linseed in a balanced diet. It's a targeted way of answering a much more specific nutritional question: how can I provide my horse with meaningful quantities of EPA and DHA directly?

Discover Synaxis Core →

Take the Omega-3 Check to see where your horse's diet stands →

Frequently asked questions

Does grass contain omega-3?

Yes. Fresh grass contains omega-3 predominantly as ALA and can provide substantial amounts when horses consume good-quality pasture.

Does hay contain omega-3?

Hay does contain omega-3, but generally less than the fresh forage it came from. The stage of growth at cutting is the biggest single influence, and the wilting and drying process alters the fatty acid profile further.⁶

Does linseed contain EPA and DHA?

Linseed is rich in ALA but does not provide meaningful quantities of preformed EPA and DHA.

Can horses convert linseed omega-3 into EPA and DHA?

Equine feeding trials have not shown a measurable rise in red blood cell EPA and DHA in horses fed ALA sources, even over 90 days and at matched omega-3 intakes.^{1 2} Feeding EPA and DHA directly bypasses the question.

Is fish oil a source of omega-3 for horses?

Yes. Fish oil provides EPA and DHA, and algae provide the same fatty acids from the organism that manufactures them.⁷

Can horses have algae oil?

Yes. Algae-derived omega-3 ingredients are used in equine feeds and supplements and provide a direct source of long-chain omega-3 fatty acids.

Is DHA the same as omega-3?

DHA is a type of omega-3. ALA and EPA are also omega-3 fatty acids, but they aren't interchangeable.

Can I feed linseed and EPA/DHA together?

Yes. They provide different fatty acid profiles, so feeding one doesn't preclude feeding the other.

How quickly does omega-3 work in horses?

Omega-3 fatty acids aren't medicines with an immediate pharmacological effect, and dietary fatty acids are incorporated into tissues over time. In the equine studies, plasma DHA peaked at around four weeks³ while red blood cell DHA was still rising between days 30 and 90.¹ Different tissues move at different rates, which is why supplementation is generally assessed over months rather than days.

The bottom line

The most useful question isn't simply whether your horse gets enough omega-3. It's which omega-3 your horse is getting.

Fresh grass, linseed and chia predominantly provide ALA, while algae (and the fish that eat them) provide the long-chain omega-3 fatty acids EPA and DHA directly. Both have a place in equine nutrition, but they aren't nutritionally identical, and understanding that distinction allows horse owners to make a much more informed decision about whether supplementation is appropriate and, if it is, what they're actually trying to supplement.