What are proteins, anyway?  They are nothing more than long chains of amino
acids, and usually have other chemical groups attached.  They make up about
50% of organic cellular material, and perform a wide variety of functions,
including working as enzymes, regulating cellular biochemistry, serving as
proteohormones, and forming the bulk of the musculoskeletal system (subtract
the protein from bone and you have salty crystals, from muscle and you have
salty, watery fat, from tendon or cartilage and you have hardly anything).
 
So why the need for special proteins (essential amino acids) and why are
some proteins so hard to digest?  The answer lies in the way the body
makes (and breaks) proteins.  Without resorting to several years worth of
biochemistry and genetics, suffice it to say that proteins are manufactured
according to strict instructions controlled by the genetic structure of
the individual, the DNA.  The exact process is a complicated one, but
essentially, if your body codes for a specific protein, then it makes it,
and if it doesn't code for it, then I doesn't make it.  It uses special
types of enzymes to link the various amino acids together, forming a long
chain which ultimately becomes the protein.
 
Trouble is, not all animals make all amino acids.  Those that are skipped
are usually due to an evolutionary trend that streamlines the biochemical
processes inside the body.  In other words, if you are consuming a food
with specific amino acids, then you no longer have a need to make them.  If
a chance mutation occurs and you lose the ability to make the amino acid,
it doesn't matter; you get plenty in your diet.  These amino acids are
called essential, because the organism cannot live without them.  It turns
out that the amino acids carnivores can no longer make are naturally found
as a major part of specific animal tissues (this is also true for humans,
and testifies to a meat-eating past).  The only source of these essential
amino acids are from animal tissue.  (I will not debate this point with
vegans who point out that people can completely subsist on vegetable
matter.  While this is true today, it has only been possible for the later
portion of this century because it requires the inclusion of foods found
all over the globe.  This was not the case even a century ago, and it only
applies to humans.  Some essential amino acids required by carnivores are
NOT produced by plants.)
 
It also turns out that the more omnivorous carnivores, like bears, raccoons
and dogs, require fewer animal-tissue amino acids than the more pure
carnivores like cats, mongeese and weasels.  Taurine is a good example.  It
is required by cats but not dogs, and if not supplied in the proper amounts,
then the cat will sicken, lose vision and eventually die.  Can carnivores
store the essential amino acids?  Not really.  Yes, some can be stored in
the blood, some even in other areas (debatable), but for the most part,
amino acids are not stored in any appreciable quantities for any more than
a few days.  And that is the problem.
 
When a cell is making a protein, it begins inside a "soup" of amino acids.
It strings the protein out one amino acid at a time, with special enzymes
snatching each necessary amino acid out of the soup in turn and connecting
it within the sequence.  Other special enzymes are cranking out copies of
the amino acids, but since there is no DNA coding for the essential amino
acids, the cells cannot make them.  So it takes them in from the blood
(ultimately from the gastrointestinal tract) and uses those.  But what if
you run of of the supply within the blood because you are no longer eating
the food with the essential amino acids?  Then protein systhesis stops.
It waits for the next amino acid in the sequence, but none is there to
drop in, so it is like a chain-maker that has run out of links.  Without
the essential amino acid, you cannot make the protein.
 
Digesting a protein is a wonder of nature.  Special enzymes rush in and
clip the protein molecule in shorter lengths, then other come in and break
it down into amino acids.  It takes specific enzymes to break specific bonds
at specific places, which is why some proteins (like hair) are difficult to
digest and others (like muscle tissue) are much easier.  This is also one of
several reasons why plant proteins are so hard to digest (others being they
are encased in a cellulose cell, and the bowel transit time being so rapid
in carnivores).  As a consequence, plant proteins are harder for primary
carnivores to digest.
 
The same types of things are true with fats, except now you are using fatty
acids instead of amino acids.  That is why fats are so important to
carnivores; they have lost the ability ot make some of them, and must
consume them to make the long fatty acids chains.  Remember the part about
50% of a cell is protein?  Well, excluding water, most of the rest is fats.
In fact, the primary part of all cell membranes is fat (lipids), studded
with various proteins which act as portals to let substances in and out.
 
What are the essential amino and fatty acids for ferrets?  Good question.
Despite an extensive search for the last several months, I cannot find a
single source that explains it.  I am sure somewhere deep in the bowels of
Purina (or some similar food manufacturer) someone knows, but it is not
in accessable print at this time.  But the funny thing is, knowing the
specifics is not important if you supply the basics.  Which is why ferrets
are here to begin with; if the people domesticating them, who knew nothing
about biochemistry, did not supply the essential amino acids, then the
ferrets would have died and we would be talking about cats or skunks.
 
Some might argue that pet food makers do the best they can.  Maybe.  But if
you believe that, then you have to wonder what mad cow disease is all about,
or why millions of taurine-deficient cats have suffered loss of vision, or
why the mink and ferrets that have died eating inadequate foods (see if
Marshall Farms will respond to that one).  But I ask you; if they *cared*
about the diet your pet ate, then why hide the facts behind the technobabble
on the packaging list?  Think about what a "chicken by-product" actually is;
a term that legally covers everything from discarded parts to feathers to
fecal waste.  Why use the term if you did not want to hide the ingredient?
And why use the term at all?  Because who would buy a product with "contains
chicken turds and groundup feathers" printed on the outside.
 
Bob C and 20 MO Dancing Dweezels
[Posted in FML issue 2310]