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Q: "I've noted with interest your remarks about how big your ferrets were,
    but didn't believe them until I was told by some of your visitors.
    What makes them so huge?"
 
A: Ever see one of those cartoons where a cat gets a bellows shoved in its
   mouth?   Well, I don't want the ferret to get a big head, so....
 
Growth is controlled by two very basic factors; genetics and environment.
These two factors are tightly intertwined, and it is very difficult to
tease one from the other.  In ferrets, genetics provides for a range of
sizes rather than a limit.  Assuming no pathological processes or genetic
mutations, genetics basically sets the limits on how big or how small an
ferret will be.  In other words, the ferret's DNA says, "This individual
will be at least this size, but not larger than that size." Growth is not
set in stone, which is why one identical twin can be taller than the other
even though they are genetically identical.  This allows the individual to
respond to different environments without needing genetic mutations to
survive.  So, polecats in rich environments are generally larger than those
from poor environments.  It also explains why early ferrets are described
as being smaller than polecats, yet today the reverse is true, which is
probably--in part)--due to ferrets eating a much better diet.
 
Of the environmental factors, perhaps the most important for large body
size is diet.  But only during a specific period of life, namely the time
prior to skeletal maturity, which includes prenatal, infant and juvenile
growth periods.  The reason for this is although muscle mass can make you
thicker, it is bone growth that makes you larger.  I could work out 24 hrs
a day, 365 days a year, and eat enough food to open my own waste treatment
plant, but I would NEVER reach 6 feet in height regardless of how big I
pumped my manly, massive, sexy hard muscles.
 
Bone growth is ultimately regulated by the amount of protein, energy,
minerals, and vitamins available to the bone-building cells.  Since you
need these items in exact proportions to each other, limiting any one will
depress the skeletal growth-curve.  So, if your ferret has a proper diet in
terms of fats and proteins, but it is lacking in the amounts of calcium
that it needs during its 4th week growth spurt, the ferret will be smaller
than another ferret that gets lots of calcium.  Thus, to maximize a
ferret's growth, nutrients should be given IN EXCESS of its needs during
the growth period.  The underlying reason is because when nutrients are
limited, the body will slow down bone growth in order to maintain the other
systems and keep the body alive.  Runts are usually small because of a lack
of nutrients, not genetics.
 
But that is not all.  Its very complicated, remember?  A ferret's final
size also depends on the size of the mother.  ANY doctor will tell you that
larger mothers make larger babies, as will the mothers if you can get them
to stop screaming.  Its called the "maternal effect," and it can have a
significant effect on the final size of the offspring.  Again, this is a
very plastic response to the environment, so that in food-poor areas, the
nutritional needs are not so demanding.  Cool, eh?  Maternal effect
maximizes (or minimizes) in 3-5 generations, where a big mommy results in a
big baby, then the big baby gives birth to a bigger baby, then the bigger
baby gives birth to Justice Committee republicans, the biggest babies of
them all.  Whaaa.
 
Now, a maximum maternal effect combined with excess nutrients during the
skeletal growth phase will result in a ferret that has reached its genetic
growth potential.  In other words, its about as big as it can get.  Its
also about as HEALTHY as it can get, and those health benefits will follow
it throughout its life.
 
Here's the monkey wrench to screw the whole thing up.  Neutering.  Female
neutering does not reduce final body size as much as it does in males,
because bone growth is enhanced by male hormones.  However, in males,
neutering causes the ferret to be significantly smaller (less sexually
dimorphic) because it reduces the growth rate of the skeleton.
 
Ferrets essentially reach skeletal maturity between 11 and 13 months of
age.  After their first birthday, while they can still get bulkier, they
are about as large as they are going to get.  This is, coincidentally,
about the time the other organ systems have matured, including the
reproductive system.  For overall health and maximum body size, this is
probably the best time to neuter your ferret, but no studies that I am
aware of directly support that conclusion.
 
My non-shelter ferrets are huge because they come from large, well fed
mothers who are not placed under reproductive stress.  As kits, they were
fed a high meat diet, full of fats and minerals.  When I got them, I
increased their nutrients, especially the protein and bone minerals, until
they were clearly in excess of needs.  I neuter the females at one year,
and males after their first rut.  The result is healthy, energetic, huge
animals with thick full coats, and a playfull disposition.
 
My evidence?  Carbone, in rut so has lost weight, is still heavier than 5
lbs.  Tui, also in rut, is 4.5 lbs, and G.W.  and Silly are about 4 lbs and
still growing.  Even the ladies are larger, with Amber, Jezabel and Lady
Noir just under 2 lbs.  The largest males I have ever seen originated in
Sweden, and Carbone was nearly as big, and he comes from smaller stock.
I'm not saying I have the largest ferrets in the USA; but I do think they
are approaching their genetic potential, and early diet is the key.
 
Bob C and 20 MO Big Babies Bellowing for Bone
[Posted in FML issue 2523]