Is My Dog Food Low in Carbs?
Last week we talked about the role of carbohydrates in a dog’s diet, their benefits and sources. Today we will show you how to determine the carbohydrate amount in your dog’s food so that you can easily assess whether your dog food is providing the needed energy requirements from the proper sources.
Let’s start by looking at the typical food label “crude analysis” which displays the relative amounts of the macro nutrients. Most labels show you the percentages for the following:
As you can see, there is no mention of the carbohydrate content. Some say that this is a nefarious omission by the dog food industry to obfuscate the fact that the food is carbohydrate laden due to the preponderance of lower quality ingredients. Today, we will leave that argument for others and focus instead on how to calculate the carbohydrate 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.
Though essential, there are a few situations where high ash quantity in food can be harmful. For example, dogs with crystals in their urine, and large breed puppies are two cases where the ash content needs to be appropriately reduced. Check with your vet to make sure that you dog is not especially sensitive to high ash content.
These days, the ash content is not often displayed on the 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 Carbohydrate Content
The calculation of carbohydrate 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 steps allows you to compare dry food and canned food as it adjusts for water content. As we explained in a prior post, the dry matter calculation is a simple ‘re-basing’ of the nutrient profiles after removing the water content.
Using our example above, we re-base by taking the carbohydrate amount 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.
What does this all mean for my dog?
First of all, remember that many dog food labels do not report ash in the guaranteed analysis. Use 2.5% and 8% ash values for canned and dry foods respectively if this is your case.
Secondly, we recommend that you check with your vet to make sure that your dog has no special dietary needs (e.g. protein or ash maximums).
Lastly, and assuming no special diet needs, we stick with our premise that dogs are best fed a diet high in protein and moderate in fat. In this case, stick with foods whose carbohydrate values are closer to 30% than to 70%.
References and further reading:
“Applied Veterinary Clinical Nutrition”, edited by Andrea J. Fascetti, Sean J. Delaney