A frequent question and not one that is relevant unless you are feeding very high (>10 lbs.) levels of a concentrate that is >15% fat. Integrity formulas do include whole ground flaxseed meal, best source of alpha-linolenic acid (ALA), and canola oil, a modest amount of ALA. Click here for a complete fact sheet on omega fatty acids.
The essential omega-3 (linolenic) and omega-6 (linoleic) requirements have NOT been established for horses. Therefore, the omega-6/omega-3 ratio for horses is NOT known. The ratio of omega-6 & omega-3 fatty acids for humans can NOT be applied to horses or any herbivore animal. For humans, the ratio is 1:1 to 4:1 (omega 6 to omega 3); most people think incorrectly that's the ratio is omega 3 to omega 6. Any material that implies/suggests benefits for horses are NOT base on substantive, quality research with horses and mostly the information one reads is anecdotal.
Feral horses grazing on pasture do consume the omega-3 fatty acid ALA (alpha-linolenic acid) but two major points. Most forages are less than 3% fat and ALA is poorly converted to the omega-3 beneficial forms DHA and EPA. DHA and EPA are forms through human research that have demonstrated some benefits. Primary source of DHA is cold water fish.
Now does it make sense that biologically that linoleic (omega 6) and linolenic (omega 3) fatty acids are essential fatty acids of the horse. YES. But the low fat levels of their natural food sources and a gut system that is forage driven does NOT permit a leap to conclusions that have been discovered in humans whose diet is much higher fat and have gut systems that are shorter and different in compartment numbers and capacity; thus, a diet that is different in composition of fiber, protein, fat and primary energy source. Dog’s diets are higher fat and the research with dogs is even questionable. Point of interest - omega 6 fatty acid is the one that nourishes the skin, not omega 3.