ron2
Posted : 8/26/2006 1:42:33 PM
Partially answering my own question. This is from the Merck Vet Manual.
"
Guaranteed Analysis:
This part of the label lists the minimal amounts of crude protein and crude fat and the maximal amounts of water and crude fiber on an as-fed (not dry-matter) basis. This analysis does not specify the actual amount of protein, fat, water, and fiber in the product. Instead, it indicates the legal minimums of protein and fat and the legal maximums of water and crude fiber content contained in the product. A laboratory proximate analysis lists the actual nutrient concentrations in the food, and 2 foods that have identical guaranteed analyses may have very different proximate analyses. A guaranteed analysis for protein may list a minimal level of 25%, while the product may (and usually does) contain >25%. A certain variance above or below a minimum or maximum should be expected. Consequently, whenever possible, the manufacturer#%92s average nutrient profile should be used to evaluate a food. Direct product comparisons made between like (similar water content) products (ie, dry vs dry, or canned vs canned) are generally valid. However, comparisons across different food types should be made on a dry-matter or caloric basis. As a rule of thumb, dry-food analyses can be converted to a dry-matter basis by simply adding 10% to the as-is value because most dry foods contain ~10% water (eg, a dry-food protein content of 25% on an as-fed basis is equal to 27.5% dry-matter basis). Canned food analyses can be converted to a dry-matter basis by simply multiplying by 4 because most canned foods contain ~75% water (ie, a canned food protein content of 6% on an as-fed basis is equal to 24% dry-matter basis).
[link
http://www.merckvetmanual.com/mvm/htm/bc/182904.htm#]
[/link]
Ingredient List:
Ingredients are listed in descending order of weight, on an as-fed basis, in the food. Although a food ingredient (eg, chicken) may be listed first, if that ingredient is 75% moisture, it will contribute a much smaller percentage of total nutrients to the food dry matter. In addition, an ingredient such as corn may be listed by individual types, eg, flaked corn, ground corn, screened corn, kibbled corn, etc. In this case, the total corn amount may be a significant amount of the total food dry matter, but when presented as individual types, each type appears lower on the ingredient list. No reference to quality or grade of an ingredient is allowed to be listed; therefore, it is difficult to evaluate a product solely on the basis of the ingredient list. The value of this list is limited to determining the sources of the proteins and carbohydrates for dogs or cats. This kind of information is useful when evaluating animals that are having an adverse reaction to a food, possibly due to an allergy or intolerance to one or more ingredient sources such as beef, poultry, rice, corn, etc.
Product formulations can be either fixed or open. In a fixed formula, combinations of ingredients and nutrient profiles do not change regardless of fluctuating market prices of the ingredients. In an open formula, ingredients, and possibly actual nutrient profiles, change depending on availability and market prices.
"
As said above, grain fractions can be listed and appear further down the list, even though, altogether it may make up a significant amount of the food. I hypothesize that even if the ingredient list only says ground corn, it's going to contain all parts that would ordinarily be listed as fractions. FWIW, before the extrusion process, which is not a super high heat process, a ingredients are ground to a particle size. And the reason fat is added last is because adding it earlier in the cooking process will prevent other reactions from taking place that are necessary. So, when someone says the fat is sprayed on, well of course, it is. At that point in time, that's the only way to add fat. Notice, too, that the article points out what I said before, that the percentage of protein is not defined by the ingredient list, it is defined by the GA on the as-fed basis. Each meal provides a percentage of this or that. If corn is part of the meal and corn does, in fact, contain protein and minerals, as well as carbohydrates, then part of that percentage of protein as fed will be corn-based protein. As yet, I don't know of any rule stating how much animal protein versus vegetable protein is in the as-fed profile and I'm not sure how that could accomplished, if it were so desired.
The only scientific value of the ingredient list is in tracking down a food allergy or avoiding one, if you know what it is. That is, if your dog is allergic to corn, don't feed him or her a food with corn in it. That's all the ingredient list can do for you.