In recent months, numerous people have asked I discuss a number of issues
regarding ferret diet.  For several reasons, I have been unable to
respond to the requests until now.  For this discussion, I will mention
10 ideas that are widely held, but generally mistaken.
 
I don't have time to explain questions that may be answered in follow-up
posts, so if I think a remark or question may be answered later, I will
ignore it.  After I post the final part, I will happily answer those
questions that were not discussed.  I will supply a bibliography when
finished.
 
   -------------------------------
 
Ten Myths regarding Ferret Nutrition:
 
1. Because ferrets [polecats] eat the intestines of prey animals,
carbohydrates are a natural part of the ferret's diet.
 
FALSE.  It is true that ferrets will eat the intestines of small rodents,
but they may or may not dine on the bowels of larger prey animals.
Polecats/ferrets tend to eat the head first, followed by internal organs
and muscle meat.  This general sequence of carcass consumption insures
the best parts (generally the most nutritious) are eaten first.  Why is
the head usually eaten first?  Brains are full of the essential fatty
acids, fats, and proteins a primary, obligate carnivore like the ferret
needs the most.  By the time a ferret gets around to eating the
intestines of larger animals, many free carbohydrates have been fermented
by intestinal bacteria, or the bowel has already decayed to the point
only a starving animal would try consuming it.  Even if you added the
bowel contents to a ferret's diet, the relative percentage would range
somewhere between 1-5% of the diet.  Compare this to 40-60% carbohydrates
found in the typical dry, extruded diet (kibble).  So even if 1-5%
carbohydrate is naturally consumed, that is VASTLY different compared to
what they eat when crunching kibble.
 
Another important aspect of ferret diet is the type of animals they eat.
Wild European polecats are anuran specialists, especially during the
winter months.  Adult anurans -- frogs and toads -- are also carnivores,
and lack significant carbohydrate within their bowels.  While small
rodents (rats, mice, voles) and lagomorphs (rabbits, hares) are an
important aspect of diet, polecats also eat insectivores (shrews,
hedgehogs, moles) and birds.  Many of these animals are not in the
best of shape; carnivores tend to prey upon the injured, old, sick,
and starving.  Marginal animals cannot be depended upon for bowel
carbohydrates.  It is clear that a reliance upon herbivore stomach and
bowel contents for carbohydrates would be, at best, foolhardy; the ferret
would never be able to depend on any significant amount of carbohydrate
from the intestines of their prey.
 
Ferrets are primary, obligate carnivores, meaning they PRIMARILY eat
animal tissue, and they are OBLIGATED by nutritional requirements to do
so.  They are not just carnivores, but carnivores that have specialized
in only eating flesh.  As a part of this dietary adaptation, ferrets have
the unusual ability to completely synthesize their energy needs from
proteins without suffering the toxic side effects of ketosis (systemic
or metabolic acidosis, sometimes called ketoacidosis).  While this trait
isn't unique among carnivores, it only exists in those that shun
consuming significant amounts of plant material (generally less than
5% of the total diet).  This abandonment of herbivorous materials is
reflected in the extreme simplification of the ferret's gastrointestinal
tract.  It is so well adapted that the ferret lacks a caecum, or even a
visible junction between the small and large intestines.  In other words,
the ferret's stomach and intestines are so modified to digest flesh that
it has lost the ability to digest significant amounts of carbohydrates.
 
The contents of the intestines contain nutrients far more important than
carbohydrates; vitamins and vitamin precursors, especially the B vitamins
and beta-carotenes.  The B vitamins are required to maintain healthy
blood, and beta-carotenes are Vitamin A precursors required to replenish
visual purple in the retina, among other things.  Consuming parts of the
gastrointestinal tract is important for ferret, but not for obtaining
carbohydrates.
 
These pieces of evidence (diet habits, anatomical adaptations,
physiological adaptations) suggest carbohydrates are an insignificant
aspect of a ferret's diet.  There are other adaptations, but these alone
suggest the inclusion of large amounts of carbohydrates in the ferret's
diet is inappropriate.
 
Bob C
[Posted in FML issue 3937]