Of all the information on a pet food label, the two most important are
the ingredient list and the guaranteed analysis.  They are also the most
confusing because they imply relationships which may not exist.  The
guaranteed analysis is particularly confusing because it appears to be an
analysis of the food, BUT it is really a guarantee that the food will
contain a minimum or maximum of specific food components.  Because of
this confusion, they can be trusted about as much as internet wackos.
 
GUARANTEED ANALYSIS: This is the total amount of protein, fat, fiber,
moisture and other stuff found in the food.  A lot of ferret owners use
this to make comparisons, so undue importance is placed on the percentages.
The guaranteed analysis simply means the food will have the minimum or
maximum claimed value; it is NOT an ANALYSIS of the food.  In other words,
if the label says the food is Crude Protein (min) 16%, Crude Fat (min) 2%,
Crude Fiber (max) 1%, Moisture (max) 78%, it doesn't actually mean that is
what you will find in the can!  The tested values could be protein 18%,
Fat 4%, Fiber 0.2%, Moisture 60% and still be in compliance with the law
and the label.  One other point.  Normally, when you see a component
listed, you assume it is different than the others.  Look at Hill's Feline
W/D: 35.7% protein, 8.6% fat, 33.3% carbohydrate, 8.1% fiber; 10% moisture,
3.32% ash, 0.14% taurine = 99.16.  This makes you think there are only
33.3% carbohydrates, BUT the fiber is cellulose, which IS a carbohydrate,
so the crude carbohydrate is 33.3% + 8.1% = 41.4%.  It also means a third
(33.3%) of the food is essentially sugar; digestible carbohydrates either
metabolize to glucose to burn or as fat to store.  Of course, some might
just pass on through, creating, ahem, sugar poops.
 
All the guaranteed analysis does is promise the components will not EXCEED
the guaranteed minimum or maximum values.  Like work performance from hung
over employees, you should expect the food to vary somewhat from batch to
batch.
 
CRUDE PROTEIN is the TOTAL protein in the food; good, bad and buggy.  This
is often considered to represent the amount of biologically useful protein,
but that is wrong.  Two different foods may both contain 40% crude protein,
yet one might be high quality with a high degree of biological usefulness,
and the other made of feathers, hair, horn, toenails and fur (this is an
exaggeration meant to be a joke; most foods wouldn't substitute for a
pillow).  It will not tell you the QUALITY of the protein, only the
total.  Crude protein is usually determined by extracting nitrogen and
extrapolation, NOT by actually counting proteins.  CRUDE FAT is the total
lipid content of the food, determined by extracting the lipids with
solvents, and could be anything from high quality fatty acids to rendered
grease from a teenager's forehead.  CRUDE FIBER is what is left over after
the plant material has been treated with solvents and the minerals have
been removed.  This is a fair way of determining the cellulose in a food,
BUT it underestimates other types of fiber.  The MOISTURE content is
usually determined by heating the food under carefully controlled
conditions and measuring the difference in weight.  It represents the TOTAL
moisture in the food, NOT the moisture found in each component.  Obviously,
the only thing guaranteed in a guaranteed analysis is confusion.
 
Carbohydrates are not required to be listed in the guaranteed analysis of
pet foods because if you know the amount of protein, fat, and ash, the rest
of the material has to be carbohydrates.  For example if the food is 30%
Protein, 20% fat, 10% fiber, 10% moisture, and 5% ash, all you have to do
is subtract the protein, fat and ash from 100 to get the maximum crude
carbohydrate: 100 - 30 - 20 - 5 = 45%.  Subtract the crude fiber from the
crude carbohydrate: 45 - 10 = 35% soluble carbohydrate.  Most CRUDE FIBER
in pet food is cellulose, an insoluble plant carbohydrate.  It is listed
as crude fiber because it allows the consumer to determine the amount of
edible carbohydrates in the product through subtraction.  It allows us to
be sure the carbohydrates are not processed wood chips (if processed on the
intestinal highway, are they pooter chips?).
 
ASH is essentially what is left over if you burn everything completely.  It
is primarily the mineral content of the food.  Some foods have extra ash
added to influence pH.  SUPPLEMENTS are the extra vitamins and amino acids
added to offset processing and cooking loss.  They are typically sprayed on
kibble as a light oil, which increases the fat content as well as making
the kibble more palatable.  Don't ash me again.
 
The guaranteed analysis does not represent individual ingredients, but a
homogenized mixture of ALL ingredients.  Can you pick out the chicken in
a piece of kibble?  If so, where's the moisture?  The answer to both is
"everywhere."  The guaranteed analysis is of the food as a whole, not as
separate components.  The crude protein is NOT a measurement of the amount
of chicken.  The crude protein is ALL the protein in the chicken and plant
material (and anything else containing nitrogen) regardless if the ferret
can digest it or not.  Crude protein is not a reflection of the amount of
biologically useful protein any more than the ability to complain is a
reflection of the need to complain.
 
Bob C and 16 Mo' Sugar Poopers
[Posted in FML issue 3033]