Adding Oil to a Horse’s Diet

Healthy, inside and out

Adding vegetable oil to equine feeds or to equine diets has been a standard practice for literally hundreds of years.  Old horse traders knew that adding oil could help slick up a horse for sale long before the science of measuring digestible energy was developed.

There are multiple ways that vegetable oils are added to horse diets.  A common practice among horse owners is to add various quantities of oil on top of an existing diet.  A cup of oil will weigh about 8 ounces and contain about 2,045 Kcal (Calories).  A 500 kg (1100 lb) horse at light work requires about 20 Mcal or 20,000 Kcal, so that oil would provide about 10% of the required DE per day.  For comparison, a pound of oats, as fed, provides about 1,320 Kcal, so adding oil provides a lot of Calories in a small package.

A key element to consider in adding oil on top of an existing diet is that oil adds only Calories (crude/unrefined oils may also contain some Vitamin E), so it is possible to alter the nutrient to Calorie ratios in a diet.  With the addition of moderate quantities of oil, this is unlikely to create issues.  If a substantial amount of oil is added on top of an existing diet, the diet may no longer be meeting the horse’s requirements for other nutrients.  Corn oil, soy oil and other vegetable oils may be used for top dressing diets.

Feed companies also add oil to formulated feeds and will declare the minimum amount of crude fat on the tag.  This is primarily from the oil in the grain and the added oil if above 3-3.5%.  A feed that is tagged at 7%  will generally contain about 3-4% added oil.  Internal formulations systems will also calculate the total DE of the feed, which includes energy from fat as well as from NDF (neutral detergent fiber), NFC (non-fiber carbohydrates) and protein.   This allows the company to maintain the balance of energy sources as well as appropriate nutrient to Calorie ratios.

If a product refers to Omega 3 or Omega 6 fatty acids, the actual quantity or % of each fatty acid may also be declared on the tag or on the bag.  The ingredient listing will generally identify the oil or oils that may be included in the product. 

Top dressing with oil is a common practice, which can be done successfully, when done in moderation with a careful eye on meeting the total nutrient requirements of the horse as well as the energy requirements.  Adding too much may result in other nutrient issues.

Are All Oils the Same for Feeding to Horses?

Adding oil or fat to horse diets was a common practice long before research determined the many benefits of added oil diets.  Horse traders hundreds of years ago knew that if they wanted a horse to gain weight and develop a slick hair coat, adding oil to the diet was one way to do it.

Are all oils the same? 

Like many questions in the equine world, the answer is yes and no. The common vegetable oils used in horse feeds are corn oil, soy oil and flax oil (linseed oil).  Canola oil, sunflower oil, coconut oil and palm oil are also used, but less frequently.  Animal fats, excluding fish oil, are not currently used very commonly in horse feeds in the United States due to customer concern, and potential palatability concerns.

What is the difference between fat and oil?   

There are multiple chapters in nutrition books written about fats and oils.  Animal Feeding & Nutrition, Tenth Addition, by Jurgens and Bregendahl is a standard text.  For simple practical purposes, a fat is solid at room temperature and oil is liquid due to the differences in composition.  For those of you who like the full science, fats and oils are:

  • Also referred to as lipids or ether extracts
  • Insoluble in water and soluble in organic solvents
  • Contain about 77% carbon, 12% hydrogen and 11% oxygen. 
  • They all contain about the same energy, 9.45 Mcal/kg or 4,290 Kcal/lb. 
    • This is about 2.25 times the energy content of carbohydrates.

What’s all the talk about Omega Fatty Acids?

There may be substantial differences in the Omega 3 and Omega 6 fatty acid profiles of different oils, particularly in the content of the essential fatty acids (EFAs) linoleic acid (C18:2 n-6),  linolenic acid (C18:3 n-3) and arachidonic acid(C20:4 n-6)  Arachidonic acid can be synthesized from linoleic acid and is essential if linoleic acid is not present.

  • Corn oil will be higher in linoleic acid, an n-6 or Omega 6 fatty acid. 
  • Soy oil, particularly mechanically extracted, will contain more linolenic acid, an n-3 or Omega 3 fatty acid, than corn oil. 
  • Linseed oil, from flax, contains the highest % of linolenic fatty acid. 
  • Fish oil from certain cold water sources is the highest in Omega 3 fatty acids, although it may present some palatability issues.

How are they made?

Vegetable oils come from the seed of the plant with most being in the germ.  They are produced by either solvent extraction or mechanical (squeezing or crushing the seeds) extraction.  They can either be refined or in crude form, depending on the processing. All of the vegetable oils contain essentially the same amount of energy and are generally palatable if processed and stored properly.