Dr David Wood BVSc, MRCVS

There are two reasons for including oil in a horse’s diet:

  1. As an energy source – alternative to carbohydrates like sugars and starch
  2. To supplement Omega 3 and to a lesser extent Omega 6 fatty acids.

When used solely as a substitute energy source the type of oil used is not critical to its energy effect. They all have very similar energy content, between two and a half to three times that of grains. In high performance horses working at speed, the story is more complex, and the selection of the most suitable oil requires more care.

Energy Source

Rolled Oats

Rolled Barley

Flaked Corn


Energy Content MJ/Kg as fed





Source: NRC 6th Ed.

The digestibility of oils vs. starch from grains is not a significant issue when fed at rates up to around 20% of the total energy intake. However, some conditioning of the digestive system by slowly increasing the intake over 6-8 weeks is necessary to derive the full benefit from dietary oil.

Broadly speaking there are two main benefits to sourcing part of the horse’s energy intake from oils as opposed to starch from grains:

  • Gut Effects: one danger of high grain diets for horses is starch overload, especially when grain passes undigested into the hind gut where it can precipitate sudden changes in the normal gut flora, leading in turn to the production of gas or bacterial toxins. The result can be the circulatory changes resulting in acute laminitis or colic, diarrhoea, and at a less dramatic level, behavioural changes such as nervousness and excitability.
  • Metabolic Effects: Horsemen know from long experience the link between high energy diets and the “Tying Up” syndrome but other important metabolic diseases such as insulin resistance are linked to carbohydrate metabolism in genetically susceptible horses.

Bearing in mind that the natural diet of horses was quite low in soluble carbs like starch and sugars, using fat instead of starch to provide extra energy to a performance horse, is a viable and often safer option. Fat is metabolised differently from carbohydrates and avoids the peaks and troughs in blood glucose levels associated with grain feeding which can lead to insulin resistance.

Fatty Acids (FA) are the basic units in oils and certain FA’s cannot be synthesised in the body and must be provided in the diet. These are called Essential FA’s and include the Omega 3, and Omega 6 FA’s which play a role in inflammation and the body’s response to it. Deficiency may compromise lung function, result in dermatitis, poor fertility, stunted growth and reduced inflammatory and immune responses.

Omega rich oils vary in stability, shelf life and quality and need stabilisers like anti-oxidants such as Vitamin E, to prevent rancidity. Preparation is important and for example, toxins can be produced by boiling linseed if not done properly.

OMEGA 3 . Alpha Linolenic Acid or ALA.

The horse’s natural diet of forages is high in Omega 3.

  • Omega 3’s are also found in fish oils, flax seed, canola and soy oil.
  • Helpful in inflammatory conditions such as arthritis or dermatitis (Queensland itch) and involved in red blood cell and hormone production, they also support immune function.
  • May support fertility in some stallions as well as viability of frozen semen.
  • So called “Joint Formulae” may contain fish or flax seed oils, associated with reducing inflammation. Improvements in stride length and performance have been attributed to this effect by reducing joint pain and stiffness.

OMEGA 6. Linoleic Acid or LA

Grains and many oil supplements are high in Omega 6.

  • Specifically associated with the construction and maintenance of liver cell membranes and blood platelet production.
  • Many oils, including flaxseed, sunflower and safflower contain both Omega 3 and Omega 6 fatty acids. Fatty acids from animal sources, palm oil, olive oil or blended vegetable oils tend to be low in w-6 fatty acids.
  • Sunflower oil is reported to benefit certain immune cells and reduces pulmonary inflammation in horses with airway obstruction disorders.

We do not yet know what the best ratio of Omega 3 to Omega 6 FA’s is, and it will probably vary depending on the desired effect, e.g. lung function, joint effects etc. Compared to the Omega 3 rich natural diet of forages, the modern horse diet is higher in Omega 6 which may exacerbate inflammatory responses. More grain, more pain! To restore normal balance supplementing Omega 3 is the norm.

Care should be taken with Omega 6 intake as too much may be deleterious to health. Supplementation of the diet with oils rich in Omega 6 FA such as corn oil may be undesirable in high performance horses such as race- horses. This is due to potentially increased red blood cell fragility caused by high Omega 6 diets and the use of a high Omega 3 oil for such horses would be preferable. Race- horses with Exercise Induced Pulmonary Haemorrhage (EIPH or “Bleeders”) may benefit from a high Omega 3 ratio in the diet because their red blood cells are more flexible and less fragile.

Shelf Life

All oils tend to oxidize in air and should be stored in tightly sealed containers in a cool place. The incorporation of antioxidants like Vitamin C helps to reduce oxidation (rancidity). Horses are strongly averse to the smell of rancid oil and will reject feed containing it. Recycled vegetable oil from commercial food preparation can suffer from this problem.

Horsepower Omega Oil Plus contains refined non-GMO flax seed oil with minimum 50% Alpha Linolenic Acid – Omega 3 content, stabilised with antioxidant ascorbic acid (Vitamin C).


Geor et al. Equine Applied & Clinical Nutrition 2013

Waldron. Fatty Acid Supplements in the Equine Market. Proc.Australasian Equine Sc. Symp.,Vol3,2010

Pagan et al. Fish Oil & Corn Oil Supplementation … Proc.Australasian Equine Sc. Symp.,Vol3,2010

2010 R. Vineyard, L. K. Warren2 and J. Kivipelto Effect of dietary omega-3 fatty acid source on plasma and red blood cell membrane composition and immune function in yearling horses. J. Anim Sci. 2010. 88:248-257.

2011 I. O’Connor et al. The effect of dietary fish oil supplementation on exercising horses. J. Anim. Sci. 2004. 82:2978-2984
Nutrient Requirements of Horses 6th Ed. N.R.C.

King. The latest on the Omegas ( fats) Article #7186 The Horse

Briggs. Fats in your horse’s diet. Book excerpt