Please read the article I linked for more information, as I will spare you the repetition, but the bottom line is this:
The best way to add eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is to feed sardines to your dog once a week. If you add fish oil to your dog’s food, replace the fish oil with sardines. While many of the studies showing the significant body and brain benefits of consuming DHA were conducted with fish oils, sardines are superior for many reasons.
Sardines, a sustainable fish with low mercury loads, are high in protein, and provide a complete range of trace minerals, including natural forms of zinc; a full complement of vitamins including D, B12, E and K; a full range of antioxidants; and other known (and, I’m sure, unknown) nutrients. The triglyceride and phospholipid forms of DHA found in sardines are more absorbable and stable than the ethyl ester forms in most fish oils, and may be more effective for improving brain functions and preventing cancer.
The best canned sardines for dogs are those in water with no salt added. Avoid sardines packed in soy, corn, sunflower, safflower, or other omega-6 rich oils. If the recommended amounts call for 1¼ cans of sardines, it is okay to feed two cans in one week of the month, and the other weeks feed just one can. Use the entire can of sardines within two days after opening it, and refrigerate the open can, so that the fragile fats do not go rancid.
Most dog foods do not contain DHA – which offers so many benefits for dogs! – and those that do contain DHA have a higher probability of becoming rancid. So what better way to add them than a nice can of sardines!