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Fish Oil for Horses: It’s not just for hair coat anymore!

08 Jul, 2016

Fish Oil for Horses: It’s not just for hair coat anymore!

The inclusion of fish oil in equine diets has been shown to provide the following benefits for horses:
  • Improved hair and skin condition
  • Increased rate of hoof growth
  • Increased insulin sensitivity
  • Reduced Exercise Induced Pulmonary Hemorrhage
  • Improve joint health
  • Reduce inflammation associated with arthritis
  • Improved immune function
  • Improved inflammatory response
  • Increased stamina in race horses
  • Improved reproductive performance in broodmares
  • Improved semen quality in stallions

All horses require two dietary essential fatty acids in their diet; linoleic acid (omega-6) and linolenic acid (omega-3). Linoleic and linolenic acid are considered dietary essential because the horse cannot make them in his/her body, therefore, they must be present in the diet. There are several other fatty acids that are metabolically essential that the horse is able to make on his/her own. Most noteworthy are arachidonic acid which is made from linoleic acid and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) which are made from linolenic acid. EPA and DHA are used in several different metabolic
pathways that affect immune function, inflammatory response and reproduction. The horse’s ability to convert linolenic acid to EPA and DHA is quite limited and many times the rate of conversion cannot keep up with the body’s demand for these two important omega-3 fatty acids; especially when the horse’s stress level is elevated. This is why dietary supplementation with EPA and DHA in addition to omega-3 fatty acids (linolenic acid) is often very beneficial, not only for horses, but for people as well.

Research has demonstrated rather conclusively that blood and tissue levels of EPA and DHA in the horse are directly proportional to the levels of EPA and DHA in the diet. The metabolic benefits of increased EPA and DHA levels in the body are significant and more than justify the cost of adding these omega-3 fatty acids to the diets of growing, performance and reproducing horses.

The best source for both EPA and DHA is fish oil. Some plant sources provide limited quantities of EPA, but not DHA. Algal sources provide DHA but not EPA. Fish oil is the best source of both EPA and DHA when supplementation of both is desired. Popular plant omega-3 fatty acid sources include flax seed, flax oil, borage oil, chia seed, hemp oil and black currant oil. Keep in mind that the omega-3 fatty acid in these plant sources is predominately linolenic acid, which is poorly converted to EPA and DHA in the body. In fact, research comparing the effects of flaxseed supplementation with fish oil
supplementation on prostaglandin levels in synovial fluid in horses demonstrated that only fish oil supplementation could affect inflammatory components in synovial fluid.

How have horses survived then, because fish has never been a staple of the equine diet? Green pasture grass has been and is the primary source of omega-3 fatty acids for the horse. Horses constantly grazing pasture grass often satisfy their metabolic requirement for all omega-3 fatty acids because their exercise and stress levels are well within the zone that allows the horse to acquire adequate amounts of linolenic and EPA which is then converted to DHA in the body. When we begin to impose our demands on the horse’s lifestyle we create situations where the horse can no longer acquire adequate amounts of omega-3 fatty acids.

This is due to increased stress brought on by management, training and exercise schedules combined with limited access to fresh green pasture. Most show and race horses will require linolenic acid and EPA and DHA supplementation if they are to acquire adequate amounts of these important nutrients to sustain peak performance. As discussed below, stallions in particular may benefit from DHA supplementation.

Insulin Sensitivity

Research conducted by the University of Kentucky, and Colorado State University indicates that fish oil supplementation may increase insulin sensitivity. University of Kentucky researchers looked at the effect of fish oil supplementation on exercising thoroughbreds while Colorado State University researchers looked at the effect of fish oil supplementation on reproductive performance in aged broodmares. Both laboratories reported data suggesting the fish oil supplementation had a substantial effect of insulin sensitivity in horses. Clinical observations with insulin resistant horses fed fish oil
indicates that fish oil supplementation may improve insulin sensitivity as evidenced by reduction in fatty deposits, improved hoof health, and improved overall well being. The length of time fish oil supplementation may take to exhibit these benefits visually has varied from 5 to 9 months.

Inflammatory Response and Immune Function

Inflammatory response and immune function are functionally related. Affecting one, by definition means the other is affected as well. Inflammatory mechanisms and immune function in the horse affect many different systems including hair and skin quality, allergic reactions, intestinal inflammation, hoof growth, stamina, reproductive performance in mares and exercise induced pulmonary hemorrhage (EIPH). Researchers at Oregon State University College of Veterinary Medicine reported that horses supplemented with fish oil had significantly more leukotriene B concentrations in neutophils compared to horses receiving an equal amount of vegetable oil. Texas A&M researchers reported that horses fed fish oil had significantly less synovial fluid white blood cell concentration and plasma prostaglandin E 2 as well as a trend towards lower normalized plasma fibrinogen concentrations compared to horses fed an identical diet without additional fish oil. Kansas State University and University of Florida research has indicated that fish oil supplementation may affect immune response in mares and subsequently affect their foals. Fish oil supplementation of cycling mares may affect follicle development as well. Clinical observations at breeding farms in central Kentucky indicate that fish oil supplementation may help lactational anestrous mares produce and ovulate a viable follicle and successfully return to pregnancy while still nursing a foal.


The anti-inflammatory effects of supplemental fish oil have been reported to increase stamina levels in exercising thoroughbreds by University of Kentucky researchers. This same anti-inflammatory activity may also explain reported improvements in hoof growth, intestinal inflammation and EIPH. Preliminary work at Kansas State University indicates that EPA and DHA supplementation from fish oil may reduce EIPH. Clinical observations with barrel race horses and thoroughbred race horses indicate that fish oil supplementation does reduce the incidence or severity of EIPH.


Research with stallions has indicated that DHA supplementation may improve semen quality in low fertile stallions and improve cooling or freezing characteristics for certain individuals. The key parameter appears to be improving the docosahexaenoic acid (DHA) to docosapentaenoic acid (DPA) ratio. Low DHA to DPA ratios are associated with poor semen quality and lower fertility. DHA supplementation has been shown to increase DHA to DPA ratios with subsequent improvements in stallion fertility. It appears that the more DHA is supplemented the greater the response in certain individual stallions. One report indicated 30g per day for at least 80 days may be necessary to obtain a desired response in stallions with low semen quality.

General Comment

High performance horses respond positively to fish oil supplementation because they are unable to metabolize alpha linolenic acid to EPA and DHA adequately when their physical or emotional activity levels increase. Research has demonstrated that blood EPA and DHA levels in such individuals are directly proportional to dietary intake of EPA and DHA; this observation supports the reported low conversion of alpha linolenic acid to EPA and DHA in the horse. Providing fish oil supplementation to horses in a form that is palatable and convenient can be challenging. EquiVision’s Fish Oil Factor provides EPA and DHA from fish oil concentrate in the proper balance with alpha linolenic acid from stabilized flax in a palatable meal form that is easy to feed. EquiVision’s Fish Oil Factor is the only correctly balanced omega-3 supplement on the market designed to reduce inflammatory response and help normalize immune function in horses.

fish oil factor for horses


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