You’ve probably heard about the health benefits of omega-3 fatty acids from fish oil, but does this supplement work for horses?

Fish oil is often added to diets, both human and animal, as a source of the essential omega-3 fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).

These two omega-3’s have gained a lot of attention because they can promote beneficial physiological changes in horses including: [1]

  • Improved skin and coat quality
  • Reduced inflammation
  • Weight management
  • Support for joint health
  • Improved respiratory health

Omega 3’s are a type of long-chain poly-unsaturated fatty acid (PUFA) that play an important role in equine physiology. Compared to pro-inflammatory omega 6’s like linoleic acid (LA), omega 3’s have an anti-inflammatory effect within the horse’s body.

If your horse’s diet is too high in omega 6’s, feeding fish oil could improve the omega 3:6 ratio and support a healthy inflammatory response. However, some question whether horses should be fed fish oil because they are herbivores and would not naturally eat fish.

Should You Give Fish Oil to your Horse?

Horses naturally obtain another omega-3 fatty acid – alpha linolenic acid (ALA) – from their forages and grains like flaxseed. But in order to have a beneficial effect, ALA must first get converted into EPA or DHA.

Horses can convert ALA to DHA and EPA, but this process is inefficient and does not produce sufficient DHA and EPA to confer the purported health benefits. For this reason, directly supplementing the equine diet with DHA and/or EPA is preferable.

Feeding your horse fish oil is one way to supplement their diet with DHA and EPA. Compared to plant sources which contain minimal or no DHA and EPA, fish oil is rich in these beneficial fatty acids and provides a favourable ratio of omega-3 to omega-6 fats.

However, fish are not naturally a part of the equine diet and fish oil can have a strong odor which raises palatability issues for some horses. Fish oil also has a higher cost per serving compared to other fat sources used in the equine diet.

Other marine sources, such as microalgae, are an alternative that provide high levels of DHA without the adverse odor. Microalgal DHA can be top-dressed on the horse’s feed with minimal palatability concerns.

Mad Barn’s W-3 oil provides 1,500 mg of microalgal DHA and 1,000 mg (1,500 IU) natural vitamin E in a typical serving. This supplement is a good choice for horses that require more energy in their diet to support exercise performance or healthy weight gain.

As with all dietary changes, we recommend consultation with an equine nutritionist to determine what is best for your horse. You can submit your horse’s diet and one of our equine nutritionists will provide a complementary assessment.

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Effects of Fish Oil in Horses

Feeding DHA and EPA can support numerous benefits in horses, including promoting skin and coat health, enhancing joint comfort and improving performance.

Fat is a denser energy source compared to carbohydrates and is metabolized more efficiently. Fat is considered a “cool” energy source, as it has a lower heat of digestion compared to protein and doesn’t promote hot or reactive behavior like starches/sugars.

Before we consider the known palatability issues of fish oil, let’s take a look at the proposed benefits of fish oil supplements in horses.

Improved Exercise Performance

In one study, 10 horses (a mix of Thoroughbreds and Standardbreds) were given either fish oil (containing 8% DHA and 10% EPA) or corn oil (containing 0.3% DHA and 0.05% EPA). The oils were given at a rate of 324 mg per kg of body weight for nine weeks. [3]

The horse’s daily exercise intensity increased over the nine-week period, leading to a final exercise challenge day when horses were assessed while at a moderate gallop on a treadmill.

During exercise, horses receiving fish oil had a lower heart rate suggesting better exercise tolerance. These horses also had a higher ratio of glucose to insulin, which indicates better insulin sensitivity compared to the horses fed corn oil.

Lactate, which is produced by muscles during exercise and can cause muscle fatigue, was not affected by treatment either during or after exercise.

Horses receiving fish oil had lower levels of glycerol and free fatty acids in their blood, suggesting they were not mobilizing as much fat from their adipose tissue.

By relying less on the release of fat from adipose tissue, horses fed omega-3s might not deplete their energy reserves as quickly and may be able to sustain longer periods of exercise.

Fish oil can improve insulin sensitivity and exercise tolerance in performance horses.

Anti-Inflammatory Effects

Omega-3 fatty acids have been consistently shown to reduce inflammatory markers in humans and animals.

In mature mares at maintenance, diets that contained fish oil (3% of the total diet) resulted in lower levels of inflammatory markers compared to corn oil. The researchers evaluated lung cells taken during bronchoalveolar lavage, a test that is commonly used to diagnose inflammatory airway disease in horses.

They found that lung cells taken from horses given fish oil supplements produced lower levels of pro-inflammatory factors. [4]

This suggests that horses with recurrent airway obstruction or other chronic inflammatory diseases might benefit from omega-3 supplementation to attenuate the exaggerated immune response.

Cardioprotective Effects

Omega-3 fatty acids are thought to support heart health and improve circulation by lowering the levels of fat (lipids) and cholesterol in the blood. Excess lipids in the blood can exacerbate clogged arteries leading to heart disease.

Exercising horses given fish oil had lower levels of triglycerides (fat) and cholesterol in the blood compared to horses given corn oil. [5]

High cholesterol and triglyceride concentrations can contribute to cardiovascular disease and are one of the reasons why fish oil and EPA/DHA are known to play a cardioprotective role in humans. [1]

Improved Sperm Quality

The omega-3 fatty acids DHA and EPA support antioxidant status in seminal fluid which helps keep sperm healthy.

One of the main challenges with cooling and storing sperm from stallions is the viability after storage. Boosting antioxidant status and health of sperm could result in improved viability.

Miniature Caspian stallions were supplemented with fish oil at an inclusion rate of 2.5% of their diet (on a dry-matter basis). This would be equivalent to 250 grams per day for a horse consuming a typical 10 kg of dry matter. [6]

After 60 and 90 days of supplementation, sperm concentration was significantly higher compared to non-supplemented horses. Importantly, when they looked at sperm after 24 and 48 hours of storage, motility and viability were greater in horses supplemented with fish oil.

Drawbacks of Fish Oil

Although there are clear benefits provided by the supplementation of fish oil in a horse’s diet, there are some drawbacks to horse owners:

  1. Cost
  2. Palatability
  3. Consistency and sustainability

Some fish oil products have a strong smell and some horses will not readily consume it. Compared to fish oil, oils derived from plant sources are both more palatable and more cost-effective.

However, most plant oils contain no EPA or DHA and will not provide the same benefits seen with fish oil. An exception is microalgae-enriched oils which do contain supplemental DHA.

Fish oils for animal consumption can come from a variety of sources, not all of which have high levels of DHA and EPA. Some fish oils might also have contaminants like lead and mercury which may or may not be disclosed on the product label.

Environmental concerns such as declining global fish stocks and by-catch might also factor into your decision to feed fish oil to your horses. There is also a concern regarding peroxidation and product freshness as fats that are oxidized can be harmful to feed.

These concerns can be mitigated by sourcing high quality equine fish oil supplements, but beware the potentially higher cost per dose.

Microalgal DHA for Horses

Innovations in human nutrition have provided unique sources of DHA and EPA for vegans and vegetarians who do not wish to consume animal products. These sources can also be added to the equine diet.

Microalgal DHA is derived from algae grown in controlled facilities which minimizes environmental impact and results in a pure, consistent product without risk of contaminants.

Oils derived from marine microalgae, like LG-MAX from Alltech, have high levels of DHA. [7] This is the type of algal DHA that you will find in Mad Barn’s W-3 oil supplement.

Research shows that horses fed algal oil and fish oil had higher levels of EPA and DHA in muscle compared to horses given flaxseed oil [9].

When levels of EPA and DHA are higher in the body, this results i