Very little of the omega 3s in flaxseed are available to dogs. Many cannot convert them at all, and at best only a small percentage is available. You are really better off using a quality fish oil ( make sure it is contaminant free and free of any heavy metals). Here's an article which explains it further.
BTW, Dr Messonier is a local vet that has several super holistic books out.excerpt from the The Arthritis Solution for Dogs by Dr. Shawn Messonier, DVM
Fats in the form of fatty acids have recently become a popular supplement among most veterinarians, not just those interested in holistic care. We are, in fact, just beginning to see that fatty acids may be valuable in a variety of conditions. Fatty acids were first purported to work in some pets with allergic dermatitis, and are in fact an essential part of the pet's diet. They are also prescribed for pets with dry flaky skin and dull coats. Recently, they have been advocated in pets with kidney disease, elevated cholesterol, and arthritis.
When discussing fatty acids, we're not just talking about adding some vegetable oil to the pet's diet to get a nice, shiny coat. The fatty acids of most concern are the Omega 3 and Omega 6 fatty acids. Omega 9 fatty acids have no known use in treating pets. Omega 3 fatty acids -- eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) -- are derived from fish oils of coldwater fish such as salmon and trout, and flax seed. Omega 6 fatty acids -- linoleic acid (LA) and gamma-linolenic acid (GLA) -- are derived from the oils of seeds such as primrose, black currant, and borage. Often fatty acids are added to the diet with other supplements to attain and additive effect. This is especially common in arthritic dogs, as fatty acid supplements by themselves usually fail to relieve pain and lameness.
NOTE: Flaxseed oil is a popular source of alpha-linolenic acid (LNA), an omega 3 fatty acid that is ultimately converted to EPA and DHA. However, many species of pets and some people cannot convert LNA to these other more active non-inflammatory omega 3 fatty acids. In one study (Hobbs and Bucco, 1999), flaxseed oil was ineffective in reducing symptoms or raising levels of EPA and DHA. Therefore, because supplementation with EPA and DHA is important, flaxseed oil is not recommended as a fatty acid supplement for pets.
A Closer Look
Cell membranes in the joint contain phospholipids. When the membrane is injured, an enzyme acts on the phospholipids in the cell membranes to produce fatty acids including arachidonic acid (an omega 6 fatty acid) and eicosapentaenoic acid (an omega 3 fatty acid). Further metabolism of the arachidonic acid and eicosapentaenoic acid by additional enzymes (the lipooxygenase and cyclooxygenase pathways) produce chemicals called eicosanoids. The eicosanoids produced by metabolism of arachidonic acid are pro-inflammatory and cause inflammation, suppress the immune system, and cause platelets to aggregate and clot. Many disorders are due to overproduction of the eicosanoids responsible for producing inflammation, including arthritis. The eicosanoids produced by metabolism of eicosapentaenoic acid are non-inflammatory, not immunosuppressive, and help inhibit platelets from clotting.
In general, the products of omega 3 (specifically, EPA) and one omega 6 fatty acid (DGLA) are less inflammatory than the products of arachidonic acid (another omega 6 fatty acid). By changing dietary fatty acid consumption, the eicosanoid production changes right at the cellular level, decreasing inflammation within the body.