Help understanding the numbers from FDMB resources

[Justin & Sebastian]

I need help understanding where all the various numbers I'm finding on these forum resources are coming from.

From the food chart, none of the percentages match what's on the can. Take the Wellness Core Turkey & Duck, which I'm currently trying. The food chart says 38% protein, 57% fat, 5% carb. The can says 12% protein, 8% fat, and nothing about carbs. Why is the chart saying there's 3x as much protein as the can, and 7x as much fat?

Second is from the dry-to-wet transition article, and relates to my previous post. The article says an average of 6-8oz per day. Every 5.5oz can I've ever seen says ~1 can per 6-8lbs of weight. Most cats weigh at least 10 lbs, usually closer to 12+, which puts it closer to 10-12oz per day, almost double what the article says.

I'm getting really frustrated because not only is my cat being difficult, none of the info I'm finding on here makes any sense when compared to reality.

 

[Kris & Teasel]

I think the simple answer is that the numbers on the can are "guaranteed analysis" whereas the numbers in Dr. Pierson's food chart are % calories from carbs, protein, etc. as fed. The two are not the same. You want the percent as fed.

Some info here: http://www.felinediabetes.com/FDMB/threads/confused-about-calculating-carbs.209593/#post-2321717

 

[flyingduster]

The cans only have a “minimum” level, not an actual level! And none give the carbs.

 

[Larry and Kitties]

Also, the can lists the min/max weight % of each constituent. Not that moisture (water is 78% or similar). When one determines the % from calories the moisture is not counted since it has zero calories.

 

[Elizabeth and Bertie]

From the food chart, none of the percentages match what's on the can.

With US cat foods the data on the product just gives guaranteed maximum or minimum percentages by weight. These may or may not be representative of what in in the product at any given time. To get more accurate values it's necessary to contact the manufacturer and ask for the current 'as fed' or dry matter percentages. The calculations on Dr Pierson's list have been done with values obtained from the manufacturer.

Even so, a carb percentage is rarely given. But the carb percentage (by weight) can be obtained by totting up the percentages for protein, fat, ash, fibre, and moisture, and deducting that from 100%.

Once that data has been obtained a calculation can be done to work out the percentage of calories that come from carbohydrates.
Basically that involves multiplying the values for protein and carbohydrate by 3.5, and fat by 8.5, to get the calories per 100g for each of those elements. Adding those together will give total calories per 100g.
Then, to get the 'percentage of calories from carbs' you can divide the 'calories from carbs per 100g' by the 'total calories per 100g', and then multiply by 100. That gives you the percentage of calories from carbohydrates.
...This is why the data on the label is so different from what is seen in the food charts...
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