As with meat and dairy foods, eggs are enriched by adding types of feed that are high in omega-3 fatty acids to the hen's diet. Enrichment can drop the ratio of omega-6 to omega-3 acids from the 15:1 found in conventional eggs to as low as 1:1 [sources: Rose Acre Farms; NutritionData].
While some pastured-raised hens obtain omega-3 by foraging on bugs and seed, many egg farmers control the process by feeding their hens flaxseed, fish oil or meal, and algae. Flax is rich in ALA. Fish byproducts have DHA, one of the forms of omega-3 that the human body synthesizes from ALA. Algae are among the few plants that also provide DHA. If you're thinking of buying omega-3 enriched eggs, check the company's Web site to see whether it specifies the source of the fatty acids or the amount of each form.
The omega-3 acids in eggs are concentrated in the yolk, as are the other fats and cholesterol. People who avoid egg yolks on that account will be heartened to know that some omega-3 enriched eggs are also lower in saturated fat and cholesterol than conventional eggs. Again, you may need to do some research to learn each brand's particular fat and cholesterol values.