You are right both Omega-3 and Omega-6 fatty oils are needed in the diet,
but it is the ratio of the 2 that is important.  In dogs and cats, the
ratio of O-6 to O-3 should be 5 to 1 to 10 to 1.  It is likely the ferrets
ratio would be similar to the cats.  Flax seed oil contains the O-3 alpha
linolenic acid (ALA).  ALA is roughly 53% of the flax seed oil.  Thus it
is a good source of an O-3.  However fish oil contains 2 different O-3
oils.  Fish oil contains Eicosaletraenoic acid (EPA) and Docosahexaenoic
acid (DHA).  Beef fat contains mostly O-6 oils and Arachidonic acid (AA)
AA is considered an essential fatty acid for cats and likely needed by
ferrets also.
 
The big picture is flax seed oil is good but fish oil is probably better.
That is why Iams kitten, Eukanuba kitten, Totally Ferret, and Marshall's
ferret food all have fish oil in them.  (Marshall's also uses fish as
protein source.)
 
Now for the biochemistry part, it is the position of the first double bond
from the terminal end of the oil that determines if it is an omega 3 or 6
or 9 oil.
 
Hope that helps,
Jerry Murray, DVM
 
and
 
Hi X,
Unfortunately we do not know the exact requirements of the fatty acids in
ferrets, so we have to extrapolate from what we do know from mink and from
cats.  Cats are obligate carnivores also, and their "wild diet" would be
mice, rats, and other small prey just like a ferret's "wild diet." The
problem with a diet that gets below a 5 to 1 ratio of Omega-6 to Omega-3
fatty acids is clotting inhibition.  A 1 to 1 ratio would likely cause the
animal to have severe clotting deficiencies and possibly even bleed to
death.  That is why the recommended ratio is 5-1 to 10-1.
 
Rancidity is not usually a problem as most diets use preservatives (BHA,
etc.) and/or vit E (i.e., mixed tocopherols) to stabilize the fats in the
diet.
 
Hope that clears things up,
Jerry Murray, DVM
[Posted in FML issue 3680]