Dog Food Dry Matter Basis for Protein, Fat, and Carb Analysis
Pet owners often wonder whether their dog food is high in protein, fat, or carbohydrates- the macro nutrients of the food. Unfortunately, the answer to these questions is not easily attainable from the dog food label. To calculate a dog food’s protein, fat, or carb values, the guaranteed analysis on the label must first be converted to a dry matter basis. This article, which is an update on a previously published piece, will demonstrate how to do this.
Let’s start by looking at the typical food label guaranteed (or crude) analysis which displays the relative amounts of the macronutrients. Most labels show you the percentages for the following:
As you can see, there is no mention of the carbohydrate content. But that doesn’t mean that we can’t determine that component value.
Before we show the calculation, we must take a side step and discuss another ingredient that isn’t often listed, Ash. The ash content in a food is needed to more accurately estimate the carbohydrate content.
What is Ash?
Ash is the inorganic material that remains after organic material is burnt up. Ash is made up of mineral nutrients like calcium, phosphorous, zinc, iron, etc. Ash itself is not necessarily bad– most ash comes from the bone content and minerals additives in a product. In general, dry pet food is always going to contain ash content while wet food will occasionally have it in smaller amounts.
Ash content is not often displayed on the dog food label. If it is, you will use that value when doing the carbohydrate calculation. If the ash content is not explicitly stated on the label, according to “Applied Veterinary Clinical Nutrition”, Andrea J. Fascetti, Sean J. Delaney, you can use an estimate of 2.5% for canned food and 8% for dry food.
Calculating Dry Matter Macronutrient Content of Dog Food
The calculation of the macronutrient content is a simple 2 step process. The first step is to estimate the percentage of carbohydrates on an as fed basis, and the second step is to convert it to a dry matter basis (which adjusts for water content). We will use the example label below in our calculations.
Step 1: The protein, fat, carbohydrate, ash and moisture content account for almost 100 percent of the total pre-cooking weight of any dog food. By subtracting the protein, fat, water and ash percentages from the 100 percent total, you will have a decent estimate of the total carbohydrate content. Using our example above:
100-26-16-10-7.5= 40.5% carbohydrates.
Note that the fiber is not included in this calculation because it comes from carbohydrates so it is already a part of the carbohydrate total.
Step 2: Convert to dry matter basis- this step allows you to compare dry food and canned food as it adjusts for water content. The dry matter calculation is a simple ‘rebasing’ of the nutrient profiles after removing the water content. To rebase the values, divide each macronutrient percentage by (100-Moisture %).
Using our example above, we rebase by taking the protein, fat, and carb amounts from above and divide by the dry matter (100%-10% moisture = 90% or .9). Here are the results for the main macro nutrients.
The net result of these calculations is that this example food is 45% carbohydrate on a dry matter basis. Most dog foods have a carbohydrate percentage between 30-70%, with higher values normally associated with lower quality foods that use grains and other low cost fillers to provide a disproportionate amount of the foods energy benefit.
Here is another example using a canned food. You will see a marked change in the macronutrient components because canned food has a much larger moisture content than dry food.
Work out the dry matter analysis on your own before checking below! We gave you some hints by providing the Ash and Carb values already.
Because this food is 76% moisture, the macronutrient values from the above table will need to be rebased by (100%-76%) or 24%. The answers are….anyone? Anyone? (with respect to Ferris Buehler).
Visually, look at the difference in a Pie Chart.
First, as reported in the label:
Now after adjusting for moisture:
What a difference!
What does this all mean for my dog?
First of all, check with your vet to make sure your dog does not require a special diet. Dogs are meant to eat high protein and high fat diets. This is the kind of diet they ate thousands of years ago and it is what their bodies were meant to consume. So run a dry matter calculation on your dog’s food to see how the protein, fat, and carbs stack up. If you see a high value for carbs, be wary and consider alternatives (assuming that there is no medical reason for a lower protein/fat diet). Check out our article on the average macronutrient values in dog food to determine how the food compares.
References and further reading:
“Applied Veterinary Clinical Nutrition”, edited by Andrea J. Fascetti, Sean J. Delaney
Next week we will return to our Dog Food Ingredients A to Z series. We are up to the letter “P”.