Understanding a "bit" of bone biomechanics helps to realize the risks of
tooth fracturing due to bone consumption.  There are a several different
types of bone, but the two we are most concerned about are compact bone
(compacta, or cortical bone) and spongy bone (spongiosa, or trabecular
bone).  Compact bone is a dense, hard bone that forms long bone shafts
(the diaphysis), and covers the exterior of most of the other bones in
the body.  Various types of trabecular bone makes up the bulk of round,
short, or irregularly shaped bones, is found between sheets of cortical
bone, like in the skull or ribs, and at the ends (the epiphyses) of the
long bone shafts, such as the femur or humerus.  Cortical bone structure
is dense and depending on the age of the individual could contain
Haversian canals and areas of bone remodeling.  Cortical bone has great
strength along the "grain" (the long axis of the bone), which is useful
for supporting weight, leaping, landing, and, in the ferret's case,
bouncing around while war dancing.  However, across the "grain," the bone
is brittle and easily fractured.  You can test this yourself by holding a
bone on its end and whacking it with a hammer.  The ends may crush, but,
unless you get Neanderthal on the bone, the shaft will remain intact.
However, if you lay the bone on its side and whack it with about the same
force, it will crush into splinters.  This type of strength is a function
of the physics of tubular supports, which you can illustrate with a
section of soda straw.  Cut two lengths of soda straw about three inches
long, and hold one between your thumb and middle finger.  Note the amount
of exertion required to collapse the straw.  Then, hold the second straw
between your thumb and finger and squeeze, but this time push a finger
against its middle.  The straw will collapse almost immediately; tubes
are very strong along the length of their axis, but weak against it.
This is why a ferret can fall from the table and land on its feet without
fracturing a leg, but catching the leg in a closing door will snap the
bone.
 
The other type of bone is trabecular bone, also called spongy bone
because it looks like it is composed of hundreds of cells like those
making up a sponge.  The cells are fashioned from tiny spicules of bone,
or trabeculae, which look like support struts bridging the interior walls
of the compact bone.  The spaces between the trabeculae are filled with
marrow.  In growing animals, nearly all this marrow is haemopoietic
tissue, called red bone marrow, and is responsible for the creation of
various blood cells, mostly erythrocytes (RBCs).  In older individuals,
yellow bone marrow invades the trabeculae, especially in the lower bones
of the extremities and within the vertebrae.  Often in diseased or
malnourished ferrets, the fat is depleted from the yellow marrow, leaving
it bluish or grayish in color.
 
One point about chicken bones from American sources is in order.  The
economics of chicken production encourage poultry producers to raise
chickens as fast and as large as is possible, and then place them on the
market as soon as possible.  This results in a tender and fat chicken
because it is very young, usually only a few months old.  Nearly all of
American-produced chicken fall into this category.  Because the chickens
are immature, the bone has yet to completely harden (ossify), and large
portions of the ends (epiphyses) are still cartilage.  The marrow is
usually rich and red, and generally fills the entire shaft (diaphysis).
These bones are softer and less prone to fracture than those of mature
chickens, and are filled with very healthful nutrients.  The middles of
the bone shafts are hard, but the rest of the bone is quite soft.
 
The upshot of this anatomical discussion is that characterizing a bone
as "hard", suggesting it could damage teeth, or that it will "splinter",
implying it will puncture the gastrointestinal tract, is extremely
simplistic.  It is evidence of a lack of understanding of bone anatomy,
as well as how carnivores--that is, ferrets--consume skeletal parts.
Ferrets are domesticated polecats, and polecats make a habit of consuming
bone.  Just how they do it shows they have an intimate understanding of
bone anatomy.
 
Bob C
[Posted in FML issue 4157]