Dog Food Dry Matter Basis for Protein, Fat, and Carb Analysis

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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.

Guaranteed Analysis

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:

  • Protein
  • Fat
  • Fiber
  • Moisture

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.

 

guar analysis1

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.

 ganalysis 2

 

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.

 

ganalysis 3

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).

 

ganalysis 4

 

Visually, look at the difference in a Pie Chart.

First, as reported in the label:

ga chart

Now after adjusting for moisture:

ga chart after

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:

http://www.petcarerx.com/c/628/dogs/food-nutrition/ash-in-pet-food-filler-or-nutrient

http://www.fda.gov/animalveterinary/newsevents/fdaveterinariannewsletter/ucm130726.htm

“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”.

image We’re joining the Tasty Tuesday Blog Hop sponsored by Sugar, the Golden Retriever and Kolchak from Kol’s Notes:

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16 Comments

  1. Such a detailed Analyzis, thank you for sharing
    YourSpecialDog recently posted…A sweet BulldogMy Profile

  2. wow great post!
    The wet food did contain a lot less Ash to. I must admit, I have heard ash is in dog food and things like that, but never really took the time to learn any info on it! So it was great to read about that today!
    ((hugz)) from your Husky Pals!
    Jenna,Mark “HuskyCrazed” Drady recently posted…Tis the season!My Profile

  3. Thank you so much for explaining this! I’ve been trying to work this out for months and finally gave up.
    Kimberly Gauthier recently posted…A PetBox Subscription Saves Money for Multi Dog HomesMy Profile

  4. We always read labels but sometimes don’t know what we are reading. Thanks for all your time and great analysis.
    jan recently posted…Artist Geoge Rodrigue has died but his little Blue Dog will live foreverMy Profile

  5. Excellent information. Thanks for sharing it in terms regular people can figure out.
    Sand Spring Chesapeakes recently posted…Glory’s Lone Pheasant HuntMy Profile

  6. Wow, this is detailed. I’m thinking there are very few Jones treats that have any carbs at all. Hm.
    Flea recently posted…Making Dogs Smile the All Natural WayMy Profile

  7. Thank you for the information. I definitely need to examine Bentley’s food habits. As I looked down your blog, all he say was the word “pie”…that can’t be a good sign!

  8. Way too much math for this pup. We will just stick with what was recommended to us and looks okay on a chart of good foods. Luckily we have no diet issues right now.
    emma recently posted…A Christmas Morning Tradition | GBGV | Tasty TuesdayMy Profile

  9. I tried to follow along based on the foods we feed, but I got a bit confused. I don’t see ash called out on the guaranteed analysis, so I got stuck. Normally I just look at the percentage of protein and fat and the protein and carb sources. We like at least 25 percent protein and 15 percent fat in a dry food.
    2 brown dawgs recently posted…Tasty Tuesday–Smooches Product ReviewMy Profile

    • Like we wrote, the Ash content is normally not in the label, so you need to estimate it.

      I would recommend that you look at your food because for a dry food with 25% protein and 15% fat, that implies a fairly high carb content! Send us a note with the exact brand and recipe and we can do the calcs for you.
      steve recently posted…Wordless Wednesday 12-18-13My Profile

      • Thanks for the answer. You did say that about the ash…lol. We like at least 25 protein and 15 fat in our foods, but that is our baseline. That is to keep keep weight on them. We have found that if we go below they will not maintain their weight.
        2 brown dawgs recently posted…Tasty Tuesday–Smooches Product ReviewMy Profile

  10. Great write up. It still makes my head spin. I know where to come though if I want an explanation of the calculation I can actually understand and follow 🙂

    I got an error again when I tried to submit my comment the first time. Something about Javascript. It may be on my end but it is confusing because sometimes it works. If it keeps happening I will look into it on my end more.
    Jessica recently posted…Yes, Chester and Gretel Have a MomMy Profile

  11. This was a highly informative and highly relevant post regarding dog food ingredients. I feel that if everyone had access to this information they would make much smarter and healthier choices when buying their dog’s food. I look forward to reading more!
    Gourmet Dog Food recently posted…Grand Opening of Urban WolfMy Profile

  12. I really wanted everything for my dog perfect and good for her especially the food. I always see to it that the food is good for her and nutrition is balanced.
    Wellness Dog Food recently posted…Dog fartsMy Profile

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