Equine Research
Very little research has been done into dietary requirements for these fatty acids in horses. Thanks to a growing interest in "healthy fats" for prevention of heart disease in humans, though, we do know a lot more about what a horse's natural intake would likely be.
Grasses contain anywhere from four to six times as much omega-3 alpha-linolenic acid as they do omega-6 alpha-linoleic acid. This means that a horse would normally take in a much higher level of omega-3s than omega-6s.
Unfortunately, omega-3 fats are very fragile. When grass is cut, the omega-3 content is rapidly lost. The omega-6 fatty acids are a bit more resistant to breakdown. Hay, therefore, is lower in omega-3 compared to omega-6 than fresh grass.
The situation just gets worse if you feed vegetable oils, grains, seeds, or high-fat seed meals. These are also high in omega-6 fatty acids. The only readily available feed ingredient high in omega-3 fatty acids is flaxseed.
A horse on a diet of 100% fresh grass will take in as much as 15 grams/day of the anti-inflammatory omega-3 fatty acids and about a quarter as much omega-6 fats. Horses on diets of hay and grain (plus seeds and brans) will have a reversed ratio-more inflammatory omega-6 than omega-3 fatty acids.
Diets higher in omega-6 fats than omega-3 fats can interfere with the use of what omega-3 fats the horse has available. This is because the enzyme that starts the plant fatty acids on their pathways inside the horse is the same for both linoleic as linolenic acid. And when one type of fatty acid is present in excess of another, it can monopolize or "hog" that enzyme. (See the chart on page 49.)
The Bottom Line
Supplementing to keep the ratio of your horse's intake of essential omega-3 and omega-6 fatty acids in amounts and proportions similar to those in fresh grass seems wise. Flaxseed remains the best way to accomplish this. Feed between 2 and 4 ounces per day (use higher amounts for horses on grain) of either freshly ground whole flaxseeds or an equine ground stabilized flax supplement.
