Yes, you heard me right – you need to stop using the guaranteed analysis to compare dog food brands. You need to convert that guaranteed analysis to either a dry matter or percent calorie basis. There are several different reasons for this. But mostly this just comes down to the fact that the guaranteed analysis is not an accurate way to compare composition of different foods.
In order to give you a firm understanding of why we don’t use a guaranteed analysis to compare dog foods we will be covering several different topics including:
- What a Guaranteed Analysis Is
- What a Guaranteed Analysis is used for
- The limitations of the Guaranteed Analysis in Dog Food
- What a Dry Matter Basis in Dog Food Is
- How to Convert the Guaranteed Analysis to a Dry Matter Basis in Dog Food
- The limitations of a Dry Matter Basis
- What a Percent Calorie Basis in Dog Food Is
- How to Convert the Guaranteed Analysis to a Percent Calorie Basis in Dog Food
This post contains THREE free calculators to make it easier for you to covert the guaranteed analysis to a percent calorie basis, dry matter basis and grams per 1000 kcal (Metabolizable Energy or ME).
What is a Guaranteed Analysis?
If you have ever checked out your dog food bag before you have probably seen the guaranteed analysis on the package. This analysis is required by AAFCO in order to sell pet food internationally or across state lines within the USA. There are four required sections to the Guaranteed Analysis – Crude Protein, Crude Fat, Crude Fiber and Moisture. Some Guaranteed Analysis may contain additional information such as essential amino acids, vitamins, minerals, or fatty acids – however this information is not required by AAFCO.
In order to sell a pet food (or treat) the label must contain a guaranteed analysis that has been created by sending a sample of the product to a laboratory for testing. However it is important to note that the guaranteed analysis is not completely accurate, and can be limited or not include some values. So let's discuss.
What is Crude Protein?
Crude protein is an estimate of total protein content of a food based on nitrogen content. On average protein contains about 16% nitrogen. So scientists estimate total protein by multiplying the nitrogen content of a food by a constant. That gives the “crude protein” of the product. The issue with crude protein is there are other nonprotein nitrogen compounds within foods – thus this may elevate protein values.
Crude Protein also give no indicator of the digestibility or bioavailability of the protein. For example leather is actually 60% crude protein. However, it obviously is a very poorly digestible and bioavailable protein source for dogs.
What is Crude Fat?
Crude fat is an estimate of lipid (fat) content based on extraction with an ether. Basically with this extraction method it gives a value that includes organic acids, oils, pigments, alcohols, and fat soluble vitamins. However, it misses or does not include all complex lipids such as phospholipids. These fats are found in meats, eggs, fish, milk, seed/nut oils, and soy. Thus the “crude fat” content may underestimate total fat content of the dog food.
AAFCO also only requires minimum fat content to the specified, not maximum. This means that true fat content of foods may be well above the minimum crude fat value listed on the pet food label. For dogs who require controlled lower fat diets using a product that has both a guaranteed minimum and maximum may be ideal.
What is Crude Fiber?
Crude fiber is a measurement of the residue that remains after the food is treated with both an acid and alkali solvent and minerals have been extracted. This mostly measures insoluble fiber or cellulose within a food. Making it not a reliable way to measure other types of fiber like soluble fiber. This means that “crude fiber” often underestimates the total fiber content of pet foods.
What is Ash?
Ash is simply what is left if you were to literally burn the food. These are usually minerals within the food. Most dry foods contain between 5-8% Ash, and most wet foods contain between 1-2% Ash. AAFCO does not require pet foods to disclose ash content of diets. However this information can give us more accurate calculations of metabolizable energy (which we will talk about below!).
Moisture in Dog Food?
The last AAFCO required nutrient is moisture. Moisture can range in dog foods from 5% for dehydrated, air-dried or freeze-dried products to over 85% in wet products. Moisture content is probably the largest influence on nutritional values presented in the guaranteed analysis and can heavily skew numbers. Canned foods may list fat percentages of only 5% on the guaranteed analysis, however true values may actually be well over 40%. Making it almost impossible to compare diet types – such as wet vs. dry dog foods – based on guaranteed analysis alone. Instead we look to comparison of composition on a dry matter or percent calorie basis.
The Problem with Guaranteed Analysis to Compare Dog Foods
The main issues with using the guaranteed analysis to compare dog foods is that: (1) it includes moisture, and (2) is affected by the caloric density of the food. In order to remove these factors and allow for a more accurate comparison we have a couple options.
In order to remove moisture as a factor we can either convert the guaranteed analysis to a Dry Matter Basis. OR we can convert the guaranteed analysis to a Percent Calorie Basis. Because moisture is included in a guaranteed analysis it can make it impossible to compare moisture-rich with dry food diets
However neither of these calculations look at the caloric density of the diet.
Comparing dog food on a nutrient per 1000kcal ME (g/1000 kcal) takes takes into account the caloric density of the food item. Unfortunately, even though this is the most accurate way of comparing dog foods… It is also the most difficult to calculate or estimate. This is because many pet foods do not provide both Ash content and Caloric Density (kcal/kg) of their foods. We will be covering this in more detail later in this post.
Knowing which values you are looking at, and discussing this with your vet is extremely important – especially with medical conditions. If your veterinarian asks for you to keep fat content below 10% – the follow-up question should be “on a dry matter or a percent calorie basis”. Ideally even knowing the grams of the nutrient that your pet requires per 1000 kcal is even better.
Converting Guaranteed Analysis to Dry Matter Basis
Probably the easiest way to convert guaranteed analysis to allow for comparison between diets is to convert values to a dry matter basis. Converting the guaranteed analysis to a dry matter basis removes moisture from affecting values. This gives you are more true representation of the contents of the overall diet.
It is however important to note that dry matter does not take into consideration the caloric density of the diet. And diets of higher caloric density will have higher dry matter protein values. This the most accurate way to compare diets will be via a caloric basis (based on a typical analysis not a guaranteed analysis).
Converting Guaranteed Analysis to Dry Matter Basis 100 - % Moisture = Dry Matter of Diet % Crude Protein / Dry Matter of Diet = % Dry Matter Protein % Crude Fat / Dry Matter of Diet = % Dry Matter Fat Quick Carbohydrate Calculation: 100 - % Dry Matter Protein - % Dry Matter Fat = % Dry Matter Carbs More Accurate Long-Form Carbohydrate Calculation: 100 - % Moisture - % Protein - % Fat - % Fiber - % Ash = GA % Carbs Calculated by Difference % Carbs Calculated by Difference / Dry Matter of Diet = % Dry Matter Carbs
Converting Guaranteed Analysis to Percent Calorie Basis
There are two ways to convert the guaranteed analysis to a caloric basis. One is merely looking at the distribution of calories from protein, fat and carbohydrates. This is similar to dry matter, as it removes moisture from the equation, but still does not account for caloric density.
But the second is to look at grams of protein, fat or carbohydrates per 1000 kcal ME. According to board-certified veterinary nutritionists the best way to compare foods. This requires additional information such as Ash Content and Caloric Density (kcal/kg) to calculate. By using this calculation method we remove caloric density as a factor for comparing foods.
However it is important to note that these values are largely still estimates if based off the guaranteed analysis instead of the typical analysis. Contacting a company directly for typical analysis values to do these calculations is the most accurate.
Estimating Caloric Distribution or Percent Calories
Calculate Calories from Protein, Fat & Carbs % Crude Protein x 3.5 = calories from protein % Crude Fat x 8.5 = calories from fat 100 - % Moisture - % Crude Protein - % Crude Fat - % Crude Fiber - % Ash = GA % Carbs Calculated by Difference (CHO) % CHO x 3.5 = calories from carbohydrates cals from protein + cals from fat + cals from carbs = total calories Calculate Percent Calories (Distribution of Calories) Calories from Protein / Total Calories x 100 = % calories from protein Calories from Fat / Total Calories x 100 = % calories from Fat Calories from Carbohydrates/ Total Calories x 100 = % calories from Carbohydrates
Converting Guaranteed Analysis to grams/1000 kcal
Calculate GRAMS of Protein, Fat & Carbohydrates (% Crude Protein + 1.5)/( kcal/kg / 10,000) = grams of protein per 1000 kcal (% Crude Fat + 1)/( kcal/kg / 10,000) = grams of fat per 1000 kcal 100-(% crude protein + % crude fat + % crude fiber + ash + moisture) = carbohydrates by difference (CHO) (CHO + 1)/( kcal/kg / 10,000) = grams of carbohydrates per 1000 kcal
Once you know how many grams of protein, fat or carbs are within a food – the next piece of the puzzle is classifying that amount at “low, moderate or high”. Below is a chart that shows – generally speaking – the range. In homemade recipes a full AAFCO nutrient spreadsheet on a caloric basis should give you these values.
|Protein||25g / 1000 kcal||< 60g/1000kcal||60-90g/1000kcal||>90g/1000kcal|
|Fat||14g / 1000 kcall||<30g / 1000kcal||30-50g/1000kcal||>50g/1000kcal|
What values are we even looking for?
This is a great question – and honestly it’s not a easy answer. Ideal macro composition for your dog is based on many different factors – including life stage, body condition, muscle-condition, skin/coat condition, any con-current disease or conditions, activity level, and more. One composition is not ideal and does not work best for every dog. You need to consider your own dog’s individual needs then choose a food based on those needs. If you are unsure what your dog’s needs are, the below blog posts might be a great place to start.
- Dog Foods for Active Dogs
- Dog Foods for Weight Loss
- Puppy Nutrition 101
- Nutritional Management of Joint Disease
Remember – nutrition is not “one size fits all”, it is highly dependent on your dog’s individual nutritional needs.
About the Author: Nikki is a Registered Veterinary Technician (Veterinary Nurse) and Dog Mom with over a decade of experience with dogs and cats. Since graduation from college (BS Biology, Dip. Animal Nutrition, AS Animal Science) she has adopted two mixed breed dogs – Ranger and Ash, and has focused her time learning about pet food and nutrition.
Nikki shares information on a range of dog nutrition topics: from how to create a homemade complete and balanced dog food recipes, to how to choose a dog food. Nikki strives to give dog parents the information they need in order to make the best nutrition decisions for their pup!
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