From Diane M. Schuller:

"Be sure to add vitamin E whenever you supplement with oils.

The reason is that oils "use up" the supplies of vitamin E in the body
unless
they're replenished. It appears that this has to do with the antioxidant
nature
of vitamin E, and the tendency of fats (oils) to oxidize.

Fish body oil contains omega-3 fatty acids (EPA and DHA). Cod liver oil
contains
vitamins them as well BUT, it's important to note a difference: cod
liver oil
also contains vitamins A and D. There are a few cod liver oil brands
that also
include the omega-3 fatty acids, although to give as much of those as
you would
like, sometimes that
means you would be giving excessive amounts of vitamins A and D, so that
has to
be kept in mind. To better explain:

Cod liver oil is high in vitamins A and D: both of these are _fat soluble_
vitamins that can be overdosed. A person doesn't need to worry much about
vitamin A unless your dog has health problems, such as liver or kidney
disease,
but excess amounts of vitamin D can be dangerous and cause bone and
other health
problems. In addition, the toxic dosage of vitamin D is only 10 times the
recommended dosage, meaning it is easy to give too much:
(http://www.peteducation.com/article....&articleid=710)

Fish body oil, on the other hand, is high in omega-3 fatty acids, and
does not
include vitamins A or D. Omega-3 fatty acids are extremely healthy, and
are hard
to find in the diet, so in general, it's quite safe to supplement with fish
[body] oil regardless of what kind of diet you feed, and for most health
problems.


http://www.pinc.com/healthnews/fishoils.html
"Cod liver oils and fish oils are not the same. Cod liver oil is extracted
from cod liver and is an excellent source of vitamins A and D. Fish oils
are extracted from the tissues (flesh) of fatty fish like salmon and
herring and are good sources of EPA and DHA. Fish oils contain very little
vitamin A and D, but cod liver oil does contain EPA and DHA. However, you
would probably exceed the recommended daily intake of vitamins A and D if
you were to try to obtain therapeutic amounts of EPA and DHA from cod liver
oil."

And one more point to know:
If a person is feeding a commercial dog food that meets AAFCO
requirements (they
already contain Vit D), feeding cod liver oil or cod liver oil products
should
be done with caution -- or not at all--, especially to a growing puppy
since it
increases calcium uptake that may lead to developmental bone and joint
problems.

There aren't a lot of reliable online sources regarding vitamin E being
necessary when feeding oils (though most books cover it) ... despite
that I've
found a couple of reliable online sources:

http://www.oilofpisces.com/vitamine.html
"Fish oils are beneficial in the prevention of cancer and cardiovascular
disease. They do, however, oxidize very easily and therefore add to the
oxidant
stress on the body. An experiment was recently carried out by the U.S.
Department of Agriculture to see if an increased intake of vitamin E could
counteract this detrimental effect of fish oils. . . . The vitamin E
concentration in the red blood cells dropped very significantly when
fish oil
was ingested but more than recovered with the vitamin E supplement. It is
concluded that the negative effects of fish oil consumption can be
overcome by
taking them together with vitamin E."

and this one (but it's a human source):
http://www.healthbulletin.org/heart_disease/heart16.htm
"Always take a small vitamin E (100i.u.) whenever you take fish oils
capsules.
Fish oils and other highly unsaturated oils oxidize readily. The E will
help to
prevent that."

Hope this also is helpful to explain these differences and the importance of
giving vitamin E when feeding oils."

http://pets.groups.yahoo.com/group/H...s/message/3439