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You are here: Home / Food Guide / Pet Food Evaluation Basics / Pet Food Math 101

Pet Food Math 101

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It took Thomas Edison thousands of attempts before discovering the proper material to use for an electric light bulb filament.

Your lightbulb moment with pet food math is about to arrive!

You don’t need to be a genius to understand pet food math

light-bulbIt does help to first understand why basic pet food math is important.

We can’t accurately compare the nutrient content of different forms of pet food without first doing something to level the playing field .

When we attempt to compare canned and dry foods, the big difference is the moisture content.

Adjusting for moisture allows us to accurately compare these type different forms of food.

This simply means we compensate by subtracting the moisture from a Guaranteed Analysis value before doing a simple calculation.

We use the same moisture adjustment approach for canned or dry foods

The adjustment uses three simple steps to convert to Dry Matter (DM):

  • Step 1:  Subtract the moisture content from 100% (100% – moisture = % Dry Matter content)
  • Step 2:  Divide Guaranteed Analysis number by % Dry Matter content (GA value/ % Dry Matter content)
  • Step 3:  Multiply by 100

In other words, by removing the moisture content reflected in the Guaranteed Analysis, we reveal the Dry Matter nutrient content of each food.

Here’s how we determine the Dry Matter Protein content using the Guaranteed Analysis numbers for a dry food example:GAlabels-ex

Example Kibble Guaranteed Analysis:
Protein: 25% | Fat: 5% | Fiber: 5% | Moisture: 10%

• Step 1: Find our “Dry Matter Content” by subtracting the Moisture from 100%. 100% represents the total food content of all ingredients, including moisture.

100% (total food content)- 10% (moisture content)= 90%
90% is the “Dry Matter content” we’ll use to adjust all our other Guaranteed Analysis levels.

GADMlabels-ex
Percentages increase when the moisture is removed

• Step 2: Determine how much Protein Dry Matter (DM) is in the food by multiplying Protein by the Dry Matter %.

25% (Protein) divided by 90% (Dry Matter %)= .278%

• Step 3: Multiply by 100

.277% X 100 = 27.8% Protein DM

Pretty simple stuff, yes?

At first glance, there may not seem to be all that much of a difference with these adjusted numbers.

Adjusting for moisture is critical when comparing canned and dry foods

GAlabels-Chixcomp
Moisture levels of cans & kibble

Let’s look at a simple example which compares the Guaranteed Analysis labels of two hypothetical chicken based foods, one canned and one dry.

Canned  Chicken Chow:
Protein: 10% | Fat: 6% | Fiber: 1.4% | Moisture: 78%

Dry Chicken Kibble:
Protein: 38% | Fat: 18% | Fiber: 5% | Moisture: 10%

At first glance, it appears the dry food contains far more protein than the canned food. But we have a secret weapon to employ- the Dry Matter %!

GADM-CanChix
Removing moisture from cans

• Let’s start by using the Protein in the canned food to find our Dry Matter %:

100%- 78%= 22%

• Now we’ll adjust the Protein level using the Dry Matter %:

10% (Protein) divided by 22% (Dry Matter %)= .45%

• Multiply by 100:

GADM-ChixDry
Removing moisture from kibble

.45% X 100 = 45% Protein DM

That’s quite a difference in Protein level from where we started. Let’s see what happens when we look at the kibble using the same technique.

• Again, we’ll start by using the Protein in the dry food to find our Dry Matter %:

100% – 10% = 90%

• Now we’ll adjust the Protein level using the Dry Matter %:

DMchixcomp
Moisture removed from both

38% (Protein) divided by 90% (Dry Matter %)= .42%

• Multiply by 100:

.42% X 100 = 42% Protein DM

Woof!

Turns out the canned food actually contains more Protein DM than the kibble.

Let’s look at another can and kibble Guaranteed Analysis comparison

GAlabels-Morselcomp
Moisture levels of cans & kibble

Canned Morsels Menu:
Protein: 6% | Fat: 5% | Fiber: 1.8% | Moisture: 78%

100% − 78% = 22% Dry Matter
6% Protein / 22% Dry Matter  = 27.3% Protein DM

Dry Morsel Meat:
Protein: 27% | Fat: 8% | Fiber: 3.5% | Moisture: 11%

100%- 11% = 89% Dry Matter
27% Protein / 89% Dry Matter  = 30.3% Protein DM

DMmorselcomp
Moisture removed from both cans and kibble

In this case, the kibble has a higher dry matter Protein percentage.

Using simple Dry Matter math to level the field allows a more realistic comparison of the actual nutrient levels in different types of pet food.

Now it’s your turn!

The Guaranteed Analysis numbers on these labels from a can and dry food mix are quite different.

GAcankib
Which has more protein?

A quick glance appears to show that the mix has more protein (34% Protein) than the can (9.5% Protein).

Remember that we can’t really know how the Guaranteed Analysis of two different forms of food truly compare without first removing the moisture content from each.

Use what you’ve learned, to see which has more Protein DM.

The answer may surprise you!

Want to go further than these simple calculations?

Now that we know how to more accurately compare GA numbers between kibble and cans, your pet food math light bulb has been lit. We can use this foundation to build an understanding of how to more precisely calculate carbohydrates, calories and other nutrient levels.

To do this requires making some general assumptions or tracking down more detailed information than what is provided in the Guaranteed Analysis. We need actual numbers, rather than the range provided in the GA, as well as a better understanding of the digestibility of a food.

These numbers are often, but not always, available to you by contacting a manufacturer directly. Using these values allows us to more precisely calculate whatever we’re after for a specific situation.

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Food Guide

  • The Pet Food Industry
  • Pet Food Evaluation Basics
    • Pet Food Ingredients
    • Digestibility
    • Special Circumstances
    • Guaranteed Analysis
    • Choosing & Comparing Pet Food
    • Pet Food Math 101
    • Food Comparison Checklist
    • 10 Commandments of Choosing Healthy Pet Food
  • Getting Started with Raw Pet Food
  • Are You On Your Own With a Pet Food Recall?
  • Dog Foods at Smiley Dog
  • Cat Foods at Smiley Dog

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