Responses to questions regarding bone eating tend to be rather negative,
ranging from a simple, "I wouldn't recommend it," to the severe, "Feeding
bone to your ferrets will kill them," and all points in between.  Rarely
are the benefits of bone eating discussed (exceptions include "Give Your
Dog A Bone" and "Grow Your Pups With Bones" by Dr. Ian Billinghurst),
although a growing number of veterinarians and scientists are turning
away from the anti-bone tradition (can you call a history less than 50
years old a 'tradition"?) and embracing new studies.  In an extended
review such as this one, a discussion of benefits is more than
appropriate.  Most of these advantages have been more-or-less discussed
during various rebuttals, but since their beneficial nature is so often
overlooked, they are worth compilation within their own section.
 
Benefits of bone eating can be divided into four basic categories:
psychological, physiological, nutritional, and hygienic.
 
Hygienic benefits include plaque removal and tooth polishing, as already
discussed.  The bone fragment stimulate the gums, improving circulation,
and scrapes the tongue, helping to clean it.  While the ferret chews,
the salivary glands are stimulated, helping to wash particles out of the
mouth and maintain proper oral pH.  Salivary washing also helps maintain
a proper oral ecology, helping to reduce the risk of the type of
bacterial colonization that helps cause bad breath, gingivitis, and
periodontal disease.  Additionally, salivary washing helps reduce the
pH within the esophagus and the stomach.  Hygienic benefits also include
a reduced risk of gastrointestinal blockage caused by hairballs.  As
bone travels down the digestive tract, hair tends to become entrapped in
exposed trabeculae on large chunks of epiphyseal bone.  If the bone's
diaphysis was small enough to swallow, perhaps a mouse or rat femur, hair
is commonly trapped within the hollow diaphysis and carried outside the
body.  Usually hyaline cartilage, the slick white material on the end
of long bones, partially survives gastric digestion.  When wet and
semi-digested, fur tends to stick to it as it passes through the
gastrointestinal tract.  Overall, bone and associated particles of
cartilage acts as a transport mechanism for fur, helping to move the
slick material out of the stomach and intestines before it can ball up
and cause trouble.  It is an important part of nature's hairball remedy.
 
Many of the nutritional aspects of bone eating have been covered.  Bone
is high in fat and protein, rich in essential fatty acids, vitamins,
proteins, and minerals.  The haemopoietic tissue found the red bone
marrow is nearly a perfect food for mammalian carnivores.  The mineral
part of bone has a perfect calcium-phosphate ratio, and is easily
absorbed.  Carnivores are so well adapted to a diet that includes bone
that those eating a "meat-only" diet will develop rickets, and such a
diet during growth and development can cause other debilitating disease
and even death.  Bone is healthy for ferrets to eat, and for the most
part it is harmless and safe for the animal to consume.
 
[2-part post combined here]
 
Physiological benefits of bone eating include supplying the body with
chemical buffers that help maintain a constant body pH.  Because bone
provides the perfect ratio of mineral salts, it helps prevent or reduce
the effect of osteoporosis, a potentially serious problem in de-sexed
animals (spayed, neutered) especially those suffering from diseases that
tend to leach calcium from the skeleton.  Recent evidence suggests saliva
produced by extended periods of chewing helps reduce stomach acids in
the esophagus, preventing acid reflux and lower esophageal scarring.  A
hidden benefit for female polecats is the readily absorbable iron found
in the red bone marrow; iron can be hard for the body to absorb if it
isn't at a specific ionic arrangement.  Bone marrow has iron in a
perfect ionic configuration for absorption, helping female polecats
offset the problems of prolonged estrus.  Eating bone does not prevent
the suppression of bone marrow due to hyperestrogenism, but, it does
supply large amounts of iron and other nutrients in ratios perfect for
making blood tissue, helping to offset the problem for as long as
possible.  This is not just a benefit for intact females, but it would
be beneficial to ANY anemic ferret.
 
Psychological benefits of bone eating are controversial because they are
so difficult to prove.  While it is well known that animals use specific
behaviors to reduce psychological tension, it is unknown if chewing bone
would reduce such stress in ferrets.  However, a number of animal
behavior studies suggest domesticated animals that are allowed to express
behaviors found in their wild progenitors have lower corticosteriod
levels in their blood.  Corticosteriods (cortisol, cortisone,
corticosterone) are glucocorticoid hormones produced in the cortex of
the adrenal gland, and elevated levels have long been considered as a
physiological index of stress.  In other words, the more stress in a
ferret's life, the higher the blood levels of corticosteriods.  Stress
can be caused by pain, inescapable aggression, extended confinement,
overcrowding, boredom, disease, lack of strenuous exercise, inability to
express natural behavior, and fear (among others).  There are potential
links in long-term elevated corticosteriod levels and various health
problems, including depressed immune systems, tumor formation,
irregularities within various hormonal systems, elevated heart rate and
blood pressure (and associated heart and kidney disease), depression,
and a suite of behavioral problems.  NO research that I am aware of has
linked these problems to elevated corticosteriod levels in ferrets, and I
am unaware of ANY study looking at how corticosteriod levels in ferrets
vary with various environmental factors (caging, diet, overcrowding,
etc.).  Nonetheless, while differences exist, the basic physiological
rules that govern one species are applicable to others, and the
veterinary community may underestimate the impact of stress on ferrets.
For example, it is POSSIBLE stress may be a factor in adrenal disease,
perhaps exacerbating the problems of early neutering and photoperiodism
that are also implicated in the development of the disorder.
 
Bones are chewed for two reasons: to obtain nutrients, and as a
"downtime" activity.  Downtime activities are essentially self-indulgent
in nature, but are important stress relievers.  Chewing has been shown
to be important stress relievers in large cats, wolves, dogs, and other
carnivores.  The importance of chewing in dogs is so well known that
selling things for dogs to chew is a multi-million dollar business.
Chewing is also very important to ferrets, as those who have opened their
wallets to pay veterinarians to look for fragments of rubber or other
foreign objects lodged in the intestines of their pets can testify.
Polecats are known to habitually chew bones, and fragments of partially
consumed bones have been found within their dens and scats.  This type of
activity would constitute "free food" in that for very little energy--the
cost of chewing--a polecat could obtain important energy and nutrients
simply by chewing bones left behind from their last meal.  For an animal
with high-energy costs, this could be an extremely important source of
nutrition that could spell the difference between eating just enough to
survive until the spring, and death.  I think ferrets have an inborn
desire to gnaw bones, chewing them supplies stress-reducing satisfaction.
Can I prove it?  Just give me some time.
 
Bob C
[Posted in FML issue 4161]