The Importance of Understanding the Effects of an Ad Libitum Diet in
Ferrets
 
Two terms must be understood before this discussion can take place.
An Ad Libitum diet is one that allows feeding to take place at the
consumer's whim- -regardless of metabolic need for nutrients, the
consumer can partake of food at any time.  The other term is dietary
restriction, meaning some type of restraint is placed on the ability to
feed, such as only providing food at specific times, diluting the food
with nutritionally inert materials, or changing the composition of the
food to reduce the percentage of one component to another.  While dietary
restriction (DR) is not necessarily the same as caloric restriction (CR),
for THIS discussion they are considered synonymous, meaning DR/CR
provides ALL required nutrients necessary for healthy life, BUT
restricting the amount of caloric energy available to the consumer.
 
One erroneous assumption frequently made is that because ferrets have
constant availability to food, they are well nourished.  This assumes
that the food being offered is nutritionally sound, a finding rarely
proven in ferrets.  This assumption is dangerous because:
1) The EXACT dietary requirements of ferrets are unknown.
2) There are no legal requirements forcing ferret feed manufacturers list
nutritional soundness (as in cat or dog feeds).
3) Identical ingredients listed on the side of the box can result in
different quality of feed depending on dozens of factors, including the
exact extrusion process, source of ingredients, or storage before or
after manufacture.
4) There are scant published studies detailing the long-term effects of
nutritional deficiencies OR excesses on the health of ferrets.  This last
"raison d'etat' is what makes the assumption so dangerous; while signs
of deficiency malnutrition are obvious, it is easy to ignore the
"malnutrition of obesity" because the health deterioration is generally
gradual rather than precipitous.  Americans are particularly insensitive
to recognizing the difference between "well fed" and "over fed," defining
dietary over-indulgence as a human -- or ferret -- right.
 
In a general sense, the difference between an Ad Libitum and a
calorie-restricted diet is one of nutrient density and timing.  Calorie
restricted diets tend to be nutrient dense when compared to their Ad
Libitum counterparts, so ferrets will eat less food, and eat less
frequently (and poop less).  Herbivory is a specialization for eating a
nutrient sparse diet, so herbivores eat constantly, have digestive organs
adapted to consuming nutrient-poor, bulky foods, and rely on symbiotic
bacteria to ferment cellulose to provide important nutrients.  Carnivory
is at the opposite end of the spectrum.  Carnivores eat nutrient rich
foods, so are adapted to consuming a diet small in bulk and rich in
essential dietary requirements.  Carnivores have simplistic digestive
systems, and while most are hosts to symbiotic bacteria, the greater the
degree of carnivory, the less the importance of the intestinal flora.
Ferrets are the archetypal carnivore: teeth wholly designed to cut and
tear animal carcasses, diminutive and simplistic gastrointestinal tract,
fast bowel transit times, lack of a functional caecum, short large
intestine, and minimal intestinal flora.  They can supply their energy
needs from protein (glucogenesis), and have no dietary requirement for
carbohydrate.  Ferrets are NOT herbivores, nor are they omnivores.
They are strict, obligate carnivores, and THAT is the problem.
 
Bob C
[Posted in FML issue 3980]