FF - Conflicting Carb %

[Susan & Andy]

Andy loves the FF pate flavors, and they are convenient and not too costly for me. In making sure I get the flavors with the lowest carbs, I have found conflicting information.
For the FF Salmon & Shrimp Feast:
Dr. Pierson's chart has carbs as 1%
The list Purina emailed to me says 2.5%
The online Excel carb calculator, and other "by hand" methods to calculate come out as 9.1% carbs.
Which is the most accurate?
Thank you in advance for your thoughts and any information!

 

[manxcat419]

First of all, you have to make sure that all those calculations are based on the same thing. Dr. Pierson uses % of calories from carbs. Other calculators may use "as fed" or "dry matter" percentages, which will come out differently. Additionally, any calculator you use that uses the values off the back of the can will be less accurate because it's based on the guaranteed analysis, not the actual as fed numbers. And because the guaranteed analysis uses minimum and maximum values for things, not absolutes, you've already got a percentage of error there.

Given that all 3 methods return values below 10% carbs, it isn't unduly concerning in this instance. But I would suggest that both Dr. Pierson's values and Purina's values will be by far the most accurate...and both of those bring the carbs in as extremely low.

 

[Elizabeth and Bertie]

There are different ways of comparing carbs, and it's a matter of comparing like with like. The values are mostly, and most usefully (for our purposes), calculated as the 'percentage of calories from carbs'. This should be the same whether using wet or dry matter values, as water has no calorie value.

But there are other ways of calculating it. Some just use the percentage by weight on a wet or dry matter basis (the values will be very different depending on whether water is or isn't included). And some compare by calories from carbs per gram or ounce (wet or dry).

As April says, Dr Pierson (Catinfo.org) uses percentage of calories from carbs. 'Percentage of calories' is also used by Dr Mark Peterson, I think. And I've seen it used in veterinary research articles on feline diabetes.
The reason this method is useful for us when choosing foods for our diabetic kitties is that the evidence is that diabetic kitties have been found to do best on a diet with less than '10% of calories from carbs'. Some do better on no more than 4 - 6% calories from carbs and this (from Dr Mark Peterson, I think) has been found to be more likely to bring about remission. So, when we're choosing cat foods for our kitties, the 'percentage of calories' method is a very useful way to compare foods.

 

[Susan & Andy]

Thank you