They might not be magical cure-alls, but with benefits such as reducing inflammation and skin reactivity to allergens, omega-3 fatty acids could be considered go-to supplements for horse owners wishing to improve their horses’ health and performance.

Omega-3 fatty acids are long-chain polyunsaturated fatty acids (PUFAs), which help provide structure to cell membranes in tissues across the body. Once incorporated into cell membranes, omega-3 and -6 fatty acids can elicit a slew of metabolic effects in tissues, such as helping regulate cell signaling. Omega-3s can also be cleaved from the cell membrane to produce eicosanoids, a type of immune system messenger used to inhibit inflammation.

With horses, specifically, added PUFAs have many benefits, such as improving exercise parameters, lowering heart rate, increasing sperm production in breeding stallions, improving immune response, and potentially improving insulin sensitivity, or the body’s responsiveness to the hormone insulin signaling the removal of glucose from the blood after a meal.

Equids do not have the ability to produce PUFAs and must meet their daily requirements with dietary sources known as essential fatty acids. When we say a feed or ingredient is high in omega-3 fatty acids, we’re usually referring to the ‘parent’ fatty acid alpha linolenic acid (ALA) or its derivatives docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the most biologically active omega-3s. After ingestion and absorption of ALA, enzymes convert it to DHA and EPA. Horses, however, might have a limited ability to convert ALA to DHA or EPA.

In a study conducted at the University of Florida, ALA-supplemented equine diets failed to influence DHA or EPA levels in blood or plasma (Vineyard et al., 2010). A team from Colorado State University (CSU) determined that EPA and DHA supplementation might be needed to modify fatty acid composition in horses (Ross-Jones et al., 2014). However, another team at CSU did observe ALA ’s conversion to EPA and DHA, as indicated by increased levels of these fatty acids in study horses’ muscle (Hess et al., 2012). Obviously, there’s still a lot to understand regarding ALA versus EPA and DHA.

So, what’s the best source of omega-3 fatty acids through either ALA, EPA, or DHA? Let’s take a look.

Plant Sources

Because horses are herbivores, vegetable-derived omega-3 fatty acid sources make up most of the equine supplements on the market today. However, fats from plant sources only serve as a source of ALA and, therefore, when consumed must be converted to EPA and DHA by the body.

Forage (pasture and hay), the foundation of a horse’s diet, is a major source of nutrients, including omega-3 fatty acids. Omega-3 fatty acids make up about 55% of the fat in grass and 18-35% of the fat in hay. Granted, forages only contain about 3% total fat. But considering the amount consumed per day, forages will always be the most vital source of omega-3s in the diet purely by volume.

Canola oil, which is derived from rapeseed, has the highest omega-3 fatty acid content of the vegetable oils, although it’s still significantly lower than its omega-6 level (of its total fat content, about 11% is omega-3 fatty acids versus 21% omega-6 fatty acids).

Soybean oil is extracted from whole soybeans and, second to canola as a vegetable oil source of omega-3s, it has a total fat content that’s 8% omega-3 fatty acids versus 54% omega-6 fatty acids.

Chia seeds have one of the highest omega-3 fatty acid levels, containing 63% omega-3 as a percentage of total fat. No published research using them in equine diets exists, however, making it difficult to determine their acceptability and digestibility as an omega-3 source.

Flaxseed is produced by the flax plant, commonly grown in cool northern climates such as Canada, Montana, and North Dakota. On average, flaxseed is 40% fat with about 58% of the total fat coming from omega-3s. Horses can consume flaxseed oil or whole flaxseed, but to obtain its nutrients they should eat it ground (due to the seed’s hard outer coating).

Marine Sources

The most concentrated and biologically effective omega-3 fatty acid sources come from the sea. Algae and plankton can produce DHA and EPA, which marine animals then accumulate by consuming these organisms.

Fish oil is mainly derived from cold-water oily fish such as menhaden, herring, cod, or salmon, which serve as rich, pure sources of these omega-3s fats. Research conducted at the University of Kentucky revealed that adding fish oil to exercising horses’ diets resulted in lower heart rates, plasma glycerol, free fatty acids, and cholesterol during an exercise test than adding corn oil, a source of omega-6 fatty acids (O’Connor et al., 2004).

Algae Depending on the manufacturer or source, omega-3 fatty acids from algae can be derived from the whole-cell form (the dried microalgae itself) or oils extracted from the microalgae biomass. The species and culturing conditions are what influence the fatty acid composition, says Lori Warren, PhD, associate professor of equine nutrition at the University of Florida’s Department of Animal Sciences, in Gainesville. Manufacturers can further customize the composition for various purposes (e.g., to emphasize EPA or DHA or the proportion of each) during the oil extraction and blending process.

“It’s important to note manufacturers are using microalgae (microscopic algae)of marine origin, which is different from the algae most of us know (such as that growing in a pond or a dirty water tank),” says Warren. “Although the specifics remain proprietary, companies use different microalgae species and may co-culture them with various yeasts and bacteria to enhance biomass growth.”

In Warren’s lab, she and her colleagues fed broodmares a microalgae supplement during the last three months of gestation and first two months of lactation. “We evaluated reproductive performance of the mare, foal viability after parturition (birth), passive transfer of immunity, foal behavior, and at two months of age we evaluated foal learning using operant conditioning (target training),” she says.

They continued their evaluations of memory and learning when the foals were 6 to 8 months old (after weaning) and when they were 1 and 2. The resulting data suggest that supplementing pregnant broodmares with a relatively low amount of DHA via an algae supplement can increase DHA transferred to the foal, improve innate and social behaviors in nursing foals, and potentially improve long-term memory recall in yearlings and 2-year-olds (Adkin et al., 2013, 2015).

In 2018 Tanja Hess, DVM, PhD, associate professor in equine sciences at CSU, released information from a study performed in her lab showing that adding 10 grams of DHA helped moderate post-exercise inflammation as measured by interferon gamma and interleukin-10 (two proteins produced by the immune system) in moderately working polo horses.

Choosing a Supplement

With a slew of commercially available supplements available from a variety of sources, how do you choose the best omega-3 for your horse?

Consider the form of supplement. Most omega-3 fatty acid supplements come as meal, pellets, or oil, says Hess. Canola and soybean oil exist only in liquid form. Flaxseed can be fed as an oil or a meal (ground). Owners find plant-based ingredients to be palatable to most horses.

Marine-based PUFAs can be found as oils, powders, or pellets, but palatability can be an issue due to their “fishy” aroma. Most fish and algae supplements include odor- and flavor-masking ingredients, such as peppermint, to help prevent smell and taste issues with horses.

The omega-3 source you feed also depends on your goals:

Does your horse’s coat need some TLC?

A diet deficient in essential fatty acids can sometimes cause dry, flaky skin, particularly in frequently stalled horses or during winter when pasture isn’t as available. If, indeed, diet is the cause, supplying any form of omega-3s (ALA, EPA, or DHA) should do the trick.

Does he have allergies or asthma?

When horses with sweet itch consumed 1 pound of flaxseed per day, they experienced a significant decrease in reactivity to a Culicoides (a genus of biting midges) extract used during intradermal allergy testing (O’Neill et al., 2002; TheHorse.com/15014). 

In another study common equine asthma symptoms (e.g., coughing) and lung function improved within one week of DHA supplementation. Researchers concluded that feeding a DHA-rich product as part of a low-dust diet to horses with chronic airway disease for eight weeks was equivalent to administering a three-week course of the anti-inflammatory medication dexamethasone with a non-low-dust diet (Nogradi et al., 2015).

Need support for insulin resistance?

In research Hess performed on insulin-resistant mares, those receiving marine and flaxseed supplements were more sensitive to insulin than control mares and showed a “trend for reduction in insulin resistance,” she says (TheHorse.com/116465).

Are you managing a chronic ­inflammatory condition such as laminitis or equine metabolic syndrome?

In another study at CSU, researchers compared feeding  flaxseed to a marine source of omega-3s derived from both fish oil and algae to see how they would alter the fatty acid composition in synovial (joint) fluid and prostaglandin E₂ (an inflammatory mediator) concentrations. The team only found EPA and DHA in the synovial fluid and plasma of horses supplemented with the marine source.

Do your senior horse’s joints need extra support?

Adding omega-3s with EPA and DHA to the diets of mature horses with arthritis lowered some inflammatory markers in the synovial fluid of affected joints (Manhart et al., 2009). Research also suggests that oral supplementation of a fish- and algae-derived source of DHA and EPA confers joint tissue protection in healthy joints affected by mild synovitis, or inflammation of the synovial membrane (Ross et al., 2016).

Do you own broodmares and stallions or raise young horses?

Adding DHA to the diet can positively affect semen quality, increase passive transfer of DHA to foals, and potentially improve young horses’ learning and memory. 

The final consideration when choosing an omega-3 source is cost. In most cases plant-based sources of omega-3s will be less expensive than marine sources.

Take-Home Message

Vegetable- and marine-based sources can provide your horse with essential omega-3 fatty acids. Forages, canola oil, soybean oil, chia, and flax contain ALA, while fish oil and algae provide DHA and EPA. Choose the best omega-3 option for your horse by considering the supplement form, your goal in providing omega-3 support, and cost, and talk with a nutritionist or your vet if you have ­questions.