I found some websites with calculators but if your old school like me I found this from a site with simple math to calculate carbs based on limited information:
http://www.petmd.com/blogs/nutritionnug ... oo_bn-9KSM
No matter where your opinion falls on the carb — no carb continuum, there’s one thing that we can all agree on. It is often hard to determine just how many carbohydrates a cat food contains. Labeling regulations do not mandate that a carbohydrate percentage be listed, but you can figure it out yourself if you’re up to a bit of math.
Pet food labels must list the minimum crude protein percentage, minimum crude fat percentage, maximum crude fiber percentage, and maximum moisture percentage. They will also sometimes include a maximum value for ash. If this is not present, I use an estimate of 3% for canned foods and 6% for dry. Once you add up protein, fat, fiber, moisture, and ash, the only thing left is carbohydrate.
I just grabbed a can of my cat’s food and this is what the guaranteed analysis says:
Crude Protein (min): 12%
Crude Fat (min): 2.0%
Crude Fiber (max): 1.5%
Moisture (max): 80%
Ash (max): 3%
Therefore, this food’s carb content is 100 – (12 + 2 + 1.5 + 80 + 3) = 1.5%
Now, these answers aren’t going to be exact because we are dealing with minimums and maximums and sometimes an estimate for ash, but it’ll get you into the ballpark. (When I did this with another can of food that I know has no carbs, my result was -2.)
In comparison, my cat’s dry food guaranteed analysis looks like this:
Crude Protein (min): 38%
Crude Fat (min): 8.5%
Crude Fiber (max): 4.3%
Moisture (max): 12%
Ash (max): 6%
To calculate the carb content: 100 – (38 + 8.5 + 4.3 + 12 + 6) = 31.2%
Now both of these products report their guaranteed analyses on an “as fed” basis, meaning that comparing dry and canned foods is almost impossible due to their wildly different moisture contents. To correct for this we need to convert our result into a “dry matter” basis. Here’s how:
Find the percent moisture and subtract that number from 100. This is the percent dry matter for the food. Next divide the nutrient percentage on the label that you are interested in by the percent dry matter for the food and multiply by 100. The resulting number is the nutrient percentage on a dry matter basis.
For example, the dry food label lists its moisture content at 12% and we calculated percent carbohydrate to be 31.2%. To figure out the food’s carb level on a dry matter basis, the calculations in this case would be 100-12=88 and then 31.2/88 x 100 = 35.4%. The canned food’s calculations look like 100-80 = 20, 1.5/20 x 100 = 7.5.
So at least now you know how to figure out how many carbs are in your cat’s food.
Dr. Jennifer Coates
http://www.petmd.com/blogs/nutritionnug ... oo_bn-9KSM
http://www.petmd.com/blogs/nutritionnug ... oo_bn-9KSM
No matter where your opinion falls on the carb — no carb continuum, there’s one thing that we can all agree on. It is often hard to determine just how many carbohydrates a cat food contains. Labeling regulations do not mandate that a carbohydrate percentage be listed, but you can figure it out yourself if you’re up to a bit of math.
Pet food labels must list the minimum crude protein percentage, minimum crude fat percentage, maximum crude fiber percentage, and maximum moisture percentage. They will also sometimes include a maximum value for ash. If this is not present, I use an estimate of 3% for canned foods and 6% for dry. Once you add up protein, fat, fiber, moisture, and ash, the only thing left is carbohydrate.
I just grabbed a can of my cat’s food and this is what the guaranteed analysis says:
Crude Protein (min): 12%
Crude Fat (min): 2.0%
Crude Fiber (max): 1.5%
Moisture (max): 80%
Ash (max): 3%
Therefore, this food’s carb content is 100 – (12 + 2 + 1.5 + 80 + 3) = 1.5%
Now, these answers aren’t going to be exact because we are dealing with minimums and maximums and sometimes an estimate for ash, but it’ll get you into the ballpark. (When I did this with another can of food that I know has no carbs, my result was -2.)
In comparison, my cat’s dry food guaranteed analysis looks like this:
Crude Protein (min): 38%
Crude Fat (min): 8.5%
Crude Fiber (max): 4.3%
Moisture (max): 12%
Ash (max): 6%
To calculate the carb content: 100 – (38 + 8.5 + 4.3 + 12 + 6) = 31.2%
Now both of these products report their guaranteed analyses on an “as fed” basis, meaning that comparing dry and canned foods is almost impossible due to their wildly different moisture contents. To correct for this we need to convert our result into a “dry matter” basis. Here’s how:
Find the percent moisture and subtract that number from 100. This is the percent dry matter for the food. Next divide the nutrient percentage on the label that you are interested in by the percent dry matter for the food and multiply by 100. The resulting number is the nutrient percentage on a dry matter basis.
For example, the dry food label lists its moisture content at 12% and we calculated percent carbohydrate to be 31.2%. To figure out the food’s carb level on a dry matter basis, the calculations in this case would be 100-12=88 and then 31.2/88 x 100 = 35.4%. The canned food’s calculations look like 100-80 = 20, 1.5/20 x 100 = 7.5.
So at least now you know how to figure out how many carbs are in your cat’s food.
Dr. Jennifer Coates
http://www.petmd.com/blogs/nutritionnug ... oo_bn-9KSM
