fish
body oil is a good idea, even if the kibble you feed contains omega fatty acids already. the important omega 3 fatty acids are EPA and DHA, which
only come from marine sources. the amounts you'll find in a kibble product are rather low and a good quality fish or salmon oil product is one of the few supplements i really do recommend. sadly not everything on the market is of good quality, so if you want to use a product especially made for pets, stick to grizzly salmon oil or seapet.com fish oil. capsules sold for human consumption are ok too, just make sure they do not have any vitamin A or D added. a good maintenance dose is about 1000mg of fish oil per 20-25 lbs of body weight, which can be increased to 1000mg per 10 lbs if you need a threapeutic effect, such as for arthritis, skin problems and allergies.
i also have to address the myth of "balanced" omega fatty acids, since i often see people obsessing about this. they may be balanced in the bottle of product you are looking at, but you have no way of knowing what the ratio ends up being once you take the entire diet of an individual dog into consideration - including any treats and extras you feed.
example: the claim that hemp oil has balanced omega 3s,6s and 9s. they might be balanced if you feed your dog nothing but hemp oil, since in this situation no outside influence would change the ratios, but as soon as you bring other foods into the mix, the ratios will change inevitably.
in addition to that, ratios and requirements are not fixed. some individuals have different requirements than others. case in point: dog food X contains a ratio of 10:1omega 6 to omega 3 fatty acids. one dog does perfectly well on it, but the next has dry, itchy skin and a brittle coat. excess omega 6 fatty acids are not beneficial to the body, on the contrary - if they are present in high amounts, they increase inflammation and allergic responses. if you balance out the high amount of omega 6s in said food by adding
only omega 3s, and thus decrease the ratio to maybe 5:1 or less, the itchy dog with dull coat will most likely show a drastic improvement, since the body utilizes omega 3s before the omega 6s for its specific needs.
i'm not sure if i have explained it well enough, if not please let me know and i'll try to be more specific, but the goal with omega fatty acid supplementation is
not to maintain a certain ratio, it is to
adjust the ratio in the overall diet according to the individual animal's needs - which in turn depends on what you are feeding to begin with.
so please ignore any claims to "balanced omega fatty acids", they are just as flawed as the claims that any dog food is "complete and balanced".
some extra info:
http://www.mordanna.com/dogfood/index.php?page=efas