Everyone knows ferrets need lots of protein and fat, and more than a few
ferret owners have been spotted reading the sides of cat food boxes to see
what protein and fat percentages are contained therein.  But as some might
know than comparing foods, various moisture contents make direct comparisons
impossible, even between kibbled chows.  All is not lost, because, with a
calculator you can make direct comparisons.
 
Say food A is 10% water and 30% protein, food B is 15% water 25% protein and
food C is 50% water and 20% protein.  Which food has the highest protein
content?  Divide the protein percent by the dry food percent (the food
percent (100%) minus the water percent) to get the correct answer.  Food A
would be 30/90 or 33.33% protein, food B would be 25/85 or 29.41% protein
and food C would be 20/50 or 40% protein.  Piece of cake.  So now you are
confident that your ferret is getting the correct percent of protein, right?
Actually, all you have calculated is "crude protein;" that is, the total
amount of protein in the dry product.  Protein can be meat, it can be
tendon, or it can be skin.  It could be hair or feathers.  It could even be
fecal waste.  The crude protein percent may indicate a product is suitable
for ferrets, but without two very important pieces of information, you can
never really be sure.  Those are the protein's "biological value" and its
"digestibility."
 
The biological value of a food is dependent on the specific amino acids it
contains, as well as the nutritional requirements of the consumer.  In
other words, the biological value of a specific food can be different when
consumed by a ferret compared to a cow.  This is because a ferret, being a
carnivore, has a different list of essential amino acids (those it cannot
make in its own body) than a cow.  So, pig tendon would have a different
biological value for a ferret than when compared to the cow's amino acid
requirement list.
 
The other thing you need to know is the "Protein Digestibility."  This is
nothing more than the ability of the gastrointestinal tract to absorb the
protein.  So a hairball, close to 100% protein, would have a very low
protein digestibility index, say 1%, compared to meat, which might be 80-90%
digestible.  So, just because the protein comes from a cow, it doesn't mean
it is easily digestible.
 
Those two values, along with the protein percentage, determines how much
protein your ferret can actually get into the body at the cellular level,
and is called the "Net Usable Protein." It is calculated as (% crude protein
times biological value times % protein digestibility).  For example, suppose
three kibbles have 35% crude protein; food A has a biological value of 80
and a protein digestibility of 50%.  Food B is 72 and 70%, and food C is 37
and 90%.  Which is the better food?  Food A has a net usable protein of 14%
([.35 X .8 X .5]x 100), food B has a net usable protein of 17.64% and food C
is 11.66%.  So even though you think your ferret is getting 35% protein, it
is really only getting between 11.66% and 17.64%, depending on the food
used.
 
And where does that protein come from?  As a teenager desperately seeking
gas-powered transportation, I once earned extra money hanging chickens at
Foster Farms.  I took the chickens off the truck, clipped their feet
together, and hung them upside down on a hook connected to a belt.  The belt
dragged the chickens through a brine spray, an electrocution bath, then a
plucking machine.  Then, their heads and feet were cut off, they were bled,
then they were gutted.  The heart, liver, gizzard, and body were quickly
inspected for defects, then shipped out to the consumer.  So was the
feathers, heads, feet, blood, guts and rejected parts.  They are called
"poultry byproducts" and make up a major portion of most cat and ferret
foods.  Chicken, cow or pig, essentially the same process takes place.
"Poultry meal" can be anything from whole, ground-up chickens to ground-up
byproducts.  Unless the box says "100% cuts of beef steak; no beef
byproducts or fillers" you have *NO* idea of what is actually in the kibble.
Recently, some food manufacturers have marketed expensive products which
proclaim they are made only from top quality cuts of beef, but most never
say that because they don't contain it and misrepresentation is a crime.
Tip: stay away from food using terms like "meat byproducts," "poultry
byproduct meal," "digest," "meat meal," "poultry filler," "protein meal,"
etc.  You never know what you are feeding your ferret, but you can be sure
it is not juicy muscular tissue.
 
How does the ferret respond to this?  They generally eat more.  They have
too, because they have an instinctual drive to consume sufficient quantities
of nutrients to survive.  The trouble is, eating more often results in
obesity, not to mention more poop in the corner.  Mostly, this is because
kibbles use corn or rice meals to help hold the paste together so it can be
baked into a crunchy biscuit.  Most kibbles have a high percentage of empty
calories in the form of corn or rice carbohydrates, as well as corn syrups
and sugars.
 
One more thing about the byproducts issue.  Suppose a ferret catches and
eats a complete mouse.  If you compare the percentage of weight of the
muscle to the hormone-secreting organs, you will discover the muscle:organ
weight to be quite high.  But that is not the case with byproducts, because
you don't get much muscle meat compared to the internal organs.  There can
be a disproportionate amount of thyroids, pancreases, thymuses, adrenals,
etc., compared to an intact carcass.  There is a proven correlation between
eating such hormone-laced foods and specific diseases (including cancers) in
humans, dogs, cats, rats, and scores of other animals.
 
Am I against byproducts?  How can I be if I advocate a natural diet?  After
all, the byproducts are consumed at the same time as the rest of the mouse.
Personally, from an evolutionary standpoint, I think they should be a part
of the domestic diet in the same *proportions* as found in a natural diet,
including the proper proportions of fur or feathers.  But that is not what
you find in most commerically available ferret foods, if you can determine
what is actually there at all.
 
Bob C and 20 MO Raisin Robbers
[Posted in FML issue 2309]