Many people add oil as a top dress to their hard keepers’ rations – but do you really understand the differences between oils, and what to look for?

There are three common ways to add extra calories to your horse’s diet. More carbohydrates (typically from cereal grains), more protein (usually from alfalfa) – or more fat (from oils and meals). Cereal grains such as oats, corn, barley and wheat, along with sugar, are common sources of starch and other digestible carbohydrates, providing 4 kilocalories (kcals) per gram. Protein also has 4 kcals/g, and feeds containing soybean meal or alfalfa hay are excellent sources. But when it comes to boosting caloric intake, fat is the clear winner, with more than twice the number of calories – 9 kcals/g.

Adding fat to the diet will help your horse meet his energy needs while in training, working or performing. And unlike sugary and starchy feeds, fat (for full-sized breeds) doesn’t cause insulin to rise. It doesn’t make your horse behave badly or put him at risk for laminitis, and there’s no concern of cecal acidosis, as there would be with feeding too much grain. There are many fat sources, each with their own advantages and disadvantages.

Fats as Solids or Liquids

Fats that are solid at room temperature are typically high in saturated fatty acids. Fatty acids are long chains of carbon atoms linked together by chemical bonds. They are considered “saturated” when the carbon atoms are attached to as many hydrogen atoms as possible – making them “saturated” with hydrogens. Animal fats such as beef tallow, lard and butter are high in saturated fat. But you may not realize that tropical fats, such as coconut and palm kernel oils, are also highly saturated; in fact, they are more saturated than the grease from your hamburger! Remember that your horse is an herbivorous animal – avoid feeding him animal fat (or tropical sources).

Oils are typically liquid at room temperature, and their fatty acids are predominantly unsaturated. Chemically, this means there are missing hydrogen atoms along the carbon chain. The structure compensates for the missing hydrogen by creating double bonds. “Omega” is a naming system that classifies fatty acids according to the exact placement of these double bonds along the carbon chain. Most unsaturated fatty acids fall into one of three Omega categories: Omega-3, Omega-6 or Omega-9. Plant oils, such as soybean, corn, wheat germ, peanut, olive, canola, flaxseed and rice bran, are high in unsaturated fatty acids but their Omega types differ.

Know which Omega type you’re feeding Your horse must have two specific fatty acids in his/her diet: Omega-3, alpha-linolenic acid (ALA), and Omega-6, linoleic acid. Both are considered “essential”, meaning the horse cannot produce them. Both are found in plants. And the perfect food for horses – fresh grass – has both in their proper proportion: four times more ALA than linoleic acid. Hay, however, doesn’t have either type since these fatty acids are easily oxidized due to exposure to air, moisture, light and heat.

Fish oils are gaining popularity because of their high Omega-3 content, and contain two fatty acids: EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Your horse has the ability to manufacture EPA and DHA from ALA; therefore, they are not “essential”. It is important not to rely on fish oils to meet your horse’s Omega-3 needs, since they do not contain the essential Omega-3, ALA. Plus, horses are not fish eaters! The only time fish oil is recommended is when extreme inflammation exists – and it should be added to a diet that already contains ALA from fresh grass, flaxseed meal or chia seeds.

Linoleic acid (Omega-6), while necessary, should not exceed ALA (Omega-3), because too much linoleic acid increases the production of pro-infl ammatory eicosanoids. Unfortunately, horses typically consume far more linoleic acid than ALA, largely due to the addition of vegetable oil to commercial feeds. “Vegetable oil” can be confusing because it can be extracted from any plant; the name doesn’t tell you which one, though it is typically soybean or corn. Take a look at your feed. Does it contain added soybean or vegetable oil? If it does, is it balanced with flaxseed meal to provide ALA? Some linoleic acid is necessary, but too much Omega-6 will increase inflammation. Your goal in feeding fat is to provide more ALA than linoleic acid. If your horse is experiencing inflammation due to an injury, intense exercise/ work, aging joints, or digestive tract ulcerations, too much linoleic acid will exacerbate the situation and result in more pain.

Omega-9 fatty acids are monounsaturated. They are found in high quantities in rice bran, canola and olive oils. In human studies, Omega-9 fatty acids improve the HDL (high density lipoprotein) cholesterol component, and are therefore beneficial for protecting the heart, brain and blood vessels. However, more research is needed on their benefits for horses. We do know that Omega-9s do not increase inflammation and are therefore a safe fat source to feed.

Fresh Pasture

Forage should always be the foundation of the diet. The ideal food for horses is fresh, healthy pasture (not overgrazed, drought or heat-stressed, or weed-infested). Pasture forage typically contains 2% to 4% fat and its Omega-3 content is generally four times higher than its Omega-6 content. Once this grass is cut, dried and stored to make hay, these polyunsaturated fatty acids are destroyed by air, moisture, and heat – adding the appropriate fat source will correct this deficiency.

Fatty Acid Content of Fat Sources

The table (see below) shows the concentration of each type of fatty acid in common fat sources. Keep in mind that all fats and oils contain most fatty acid types in varying amounts. Notice that the most commonly fed oils, corn and soybean, are the most likely to cause inflammation due to their high linoleic acid content.

Some Guidelines

Limit soybean oil usage. Soybean oil has some ALA (approximately 7%) but is mostly linoleic acid (Omega-6).

Avoid corn oil and wheat germ oil. Both contain half Omega- 6s with no Omega-3s.

Restrict sunflower seeds. Sunflower oil is more than 70% Omega-6.

Add Omega-3s by feeding flaxseed meal and chia seeds. These are very high in ALA and offer an ALA to linoleic acid ratio similar to grass. Avoid feeding flaxseeds whole and do not soak them ahead of feeding. Grind your own every day (they immediately start to go rancid) or feed a commercially stabilized product.

Steer clear from hemp seed oil. It is touted as a good source of Omega-3s; however, its linoleic acid content is more than three times higher than its ALA. Reject saturated fat sources. Animal fats (e.g., beef fat and lard) and coconut oil are sometimes added to commercial feeds. Horses are not designed to metabolize large quantities of these fat sources.

Do not rely on fish oils for ALA. Fish oils can signify cantle reduce inflammation in heavily exercised horses, but should be provided in addition to a plant source of ALA.

Cereal grains are low in Omega-3s. Nearly half the fat found in grains (e.g., oats, corn, barley, wheat) comes from Omega-6s.

Rice bran or canola oil will meet additional caloric needs. Consider these once the essential fatty acid needs are met. Both are high in monounsaturated Omega-9 fatty acids. Olive oil is also beneficial (yes, some horses do like it!). If you have an insulin resistant horse, avoid rice bran (rice bran oil is okay in moderation) since it is too high in non-structural carbohydrates.

How Much Can You Feed?

An 1,100-pound horse can tolerate up to two cups of oil per day. But this amount is generally reserved for horses doing intense activity, and you would need to build up to this level over a period of six to eight weeks. If your horse needs to gain weight, a safer level would be 1/2 cup of oil, twice daily, taking three to four weeks to reach this level. Rice bran oil, canola oil, flaxseed oil, or a combination of these three, is a better choice than oils high in Omega-6s. If using flaxseed oil, limit intake to three tablespoons (45 ml) per 400 pounds (180 kg) of body weight. Rice bran is high in fat (mostly monounsaturated Omega-9s) and can be fed up to two pounds per day (if the horse is not insulin resistant since rice bran has a fair amount of starch). Flaxseed meal or chia seeds can be fed at a rate of 1/2 cup (120 ml) per 400 pounds (180 kg) of body weight.

A full-sized horse may benefit from fat supplementation, depending on his health status, exercise level, and condition. But equines such as ponies, minis, donkeys and mules cannot tolerate the high levels horses can. They can tolerate some fat supplementation, but generally 1/3 the amount given to horses.

Bottom Line

Grazing on fresh healthy pasture for at least eight hours per day will provide all the fat your horse needs, with Omega-3s and Omega- 6s in their proper proportion. When hay is the main forage source, a fatty feed or oil should be added to meet the two essential fatty acid needs, while maintaining them in proper balance. Paying attention to the type of fat in your horse’s diet can help reduce pain and inflammation, reverse illness, and optimize his performance.

Dr. Juliet M. Getty has been advising clients on how to feed their horses the way nature intended for more than 20 years. Based in Waverly, Ohio, she is a widely known and highly respected speaker, consultant and author of the comprehensive reference, feed your horse like a horse. Visit dr. Getty’s website (gettyequinenutrition.com) to browse a library of articles, a forum on nutrition, interviews and teleseminars, and sign up for her free monthly e-newsletter forage for thought.