Most pet diets are deficient in Omega 3 fatty acids
Many pets have health problems caused by too much inflammation in the body. Chronic inflammation can be a precursor for cancer or malignancy. Any disease syndrome that ends in "-itis" is inflammation: arthritis, hepatitis, cystitis, gastritis, myocarditis, dermatitis, etc. Allergies, kidney disease, and dementia (also known as cognitive dysfunction) are also caused by inflammation in the body.
Omega 3 fatty acids are naturally anti-inflammatory. In animal studies, omega-3 fatty acids were found to inhibit an enzyme called cyclooxygenase (COX), which produces the prostaglandin hormones that spark inflammation. The action is similar to what happens when one takes an aspirin, which disrupts the COX-2 signaling pathway, thus reducing inflammation and pain.
Most diets fed to pets are deficient in Omega 3 fatty acids. Grain based diets and vegetable oils are very high in Omega 6's. Omega 6 fatty acids contribute to inflammation. The ideal ratio of Omega 6 to Omega 3 in the diet is estimated to be 5:1, while most pet foods have a ratio of 30:1.
Unlike humans, dogs and cats are pretty much incapable of making Omega 3 fatty acids from Omega 6's, which is why we need to supplement Omega 3 fatty acids to the diet. The best sources of Omega 3 fatty acids are fish and fish oils.
Unfortunately, fish oil is prone to oxidation when exposed to high heat and air. This oxidation causes the oil to become rancid quickly. Rancid fish oil is worse than no fish oil in the diet.
When purchasing fish oil for your pets, be sure to buy only air-tight, lightproof packaging. Do not purchase oils in plastic bottles. The oil should be odor-free.
My favorite brand for my pets is Iceland Pure, as it fits the need for air-tight packaging, odor-free oils, high quality that is tested for impurities. I alternate between salmon oil and sardine/anchovy oil so they get the benefits of both the orange fish (salmon) and white-fish (sardine/anchovy) oils. For my dog that suffers from pancreatitis that cannot tolerate the liquid oils, I use a gelcap, which doesn't cause pancreatitis flares.