4. Dry, extruded food (kibble) is good for ferret's teeth.
 
FALSE.  Both common knowledge and advertising suggest dry, extruded foods
clean teeth of plaque and promote a healthy mouth.  However, kibble
consumption is a major cause of dental disease, and might be a factor in
the development of cardiomyopathy (dental disease and cardiomyopathy is
correlated in some species, but unproven in ferrets).  How can something
advertised as something beneficial cause such long-term damage?  The
answer lies in the composition of dry, extruded kibble, as well as its
crunchy nature.
 
There are three important reasons why kibble is bad for teeth.  First,
dry, extruded foods are composed of significant amounts of starch, so
even though the crunchy nature of the food scrapes off plaque, it also
supplies the food supply for future bacterial growth.  This is why
ferrets that eat nothing but dry, extruded food STILL have significant
problems with plaque.  Second, dry, extruded foods are composed of large
particles of cooked food that are extremely hard; what makes kibble
crunchy is also what makes it extremely abrasive.  The teeth of ferrets
that eat nothing but dry, extruded food are extremely worn.  Third,
because the particle size is larger, the "polishing" scratches are larger
as well, giving bacterial plaque more places to stick.  Dry, extruded
food is better than nothing for removing plaque in a minimalist way, but
it generally causes as many=97or more=97problems than it solves.
 
Dental wear (dental abrasion), the actual wearing down of the teeth
caused by hard particles in the diet abrading tooth surfaces, is
statistically more significant in carnivores eating dry, extruded food
compared to a meat diet that includes bone.  Dental attrition, the
formation of wear facets, occurs at the contact points of teeth, and
is a normal function of occlusion.  Carnassial teeth in ferrets are
self-sharpening; as the top tooth slides over the bottom one, dental
attrition causes wear facets that maintain a constant sharp edge along
cutting surfaces.
 
Dental wear (abrasion) is not a function of occlusion, but of diet.
Dental wear caused by diet was observed in ferrets in 1977 by Berkovitz,
who was able to easily distinguish wild polecats from laboratory ferrets,
based solely on worn teeth and plaque.  The difference between the two
groups was diet; wild polecats ate a flesh-based diet that included bone,
while ferrets were fed a dry food similar to modern pet diets.  My own
research confirms the finding.  I can mix New Zealand feral ferret skulls
with those from American pet ferrets of the same age, and easily separate
them based on dental wear and presence of plaque.  The older the ferret,
the easier it is to determine geographic origin based on dental
attributes.  The only major difference between the two groups is diet.
 
Ferrets consuming dry, extruded kibble have accelerated dental wear
compared to that of feral ferrets and polecats eating animal carcasses
containing bone.  There is some variation in the exact degree of
acceleration; usually it is 2-3 times normal, but in some ferrets, it
can be 4-5 times more than normally expected.  The variation is probably
due to variations in kibble (some are harder), kibble staleness, the
presence of oral disease, how individual ferrets chew, and/or genetic or
environmental variations in the enamel.
 
Based on careful examination of more than 400 polecat, feral ferret, and
pet ferret skulls, the effects of consuming a dry, extruded kibble diet
are predictable.  As the ferret cuts dry, extruded food with their
carnassial teeth, the hard kibble creates a series of microscratches,
easily viewed under a scanning electron microscope.  Other foods can
cause similar scratches, but because the particle size of kibble is so
large, it is like sanding with coarse rather than fine grit sandpaper.
On a continuous diet of kibble, the exterior surfaces of teeth are
abraded faster than normal, which increases the deposition rate of
dentine within the root canal.  Not only does this make it impossible
to use tooth transparency to age ferrets, but it also increases the
withdrawal rate of the tooth's blood and nerve supply.  As the root fills
with dentine, the enamel is worn away to the softer dentine underneath,
which wears away even faster.  By the time a ferret is 4-6 years of age,
the carnassials are blunt and short, the tiny molars are worn flat and
often broken or lost, and the tiny premolars are ground down to the gum
line.  In short, eating kibble accelerates the natural aging of the
teeth, setting the stage for other oral disease.
 
Bob C
[Posted in FML issue 3940]