Q: "Iams canned kitten food has 14.5% protein, 10.5% fat, 68% moisture.
    How does that compare with a dry food that is 36% protein, 22% fat and
    10% moisture?"
 
A: OoooOooooooOoO, math!! Kiss my Statistica, Baby!
 
1) Subtract the listed moisture from the total percent (100%):
100 - 68 = 32, and 100 - 10 = 90.  This is the "percent dry weight" or
"percent solids." In other words, the wet food has 32% solids and the
kibble has 90% dry weight or solids.
 
2) Divide the listed protein by the dry weight: 14.5/32 = 45.3% and
36/90 = 40.0%.  This is the "percent crude protein."  In other words, the
dry weight of the wet food contains 45.3% crude protein, and the dry weight
of the dry food contains 40.0% crude protein.
 
3) Divide the listed fat by the dry weight:
10.5/32 = 32.8% and 22/90 = 24.4.  This is the "percent crude fat." In
other words, the dry weight of the wet food contains 32.8% crude fat, and
the dry weight of the dry food contains 24.4% crude fat.
 
So, Iams canned kitten food would have 45.3% crude protein and 32.8% crude
fat, while the dry foods would have 40.0% crude protein and 24.4% crude fat.
 
However, this in NOT a fair comparison.  For example, my hair and
fingernails are "crude protein." Crude protein has NO VALUE UNLESS you
know the percentage of digestible protein and it's biological value,
something that is not typically listed on the label.  For example, suppose
the wet food had a biological value of 80 and was 95% digestible, and the
dry food had a biological value of 65 and was 90% digestible:
 
Wet Food: 45.3% x 0.80 x 0.95 = 34.4% Net Usable Protein.
Dry food: 40.0% x 0.65 x 0.90 = 23.4 Net Usable Protein.
 
11% is a BIG difference!  This particular point is moot for the example,
however, because pet foods NEVER list the net usable protein (or the
numbers to figure it out).  We never really know how to make accurate
comparisons.  To further illustrate this point, suppose we were comparing
two products, both with 40% crude protein, 30% fat and 30% carbohydrate.
Would they be comparable?  Not if mine was made of fur and chicken
feathers, old McDonalds grease and corn stalks.  The point is, the
percentages mean little if the exact ingredients are unknown.  Ingredient
lists give percentages of major components ONLY; NOT the actual nutritive
value.  Hey, don't blame me; talk to your congressmen to fix it.
 
I find the following reference a bit one sided, BUT it isn't out there in
fanatic land either.  It is an interesting read and has a lot of cat food
recipes which could be modified for ferrets (dog food as well, but don't
use them except on dogs or your spouse):
 
R. H. Pitcairn and S. H. Pitcairn 1995 "Dr. Pitcairn's Complete Guide
to Natural Health for Dogs and Cats." Rodale Press; Emmaus, PA.  383pp.
(ISBN 0-87596-243-2).
 
Bob C and 16 Mo' Incredible Carnivores
[Posted in FML issue 3029]