Dog Food: Why looking at protein percentages alone doesn’t tell you much
Every day I get many questions about protein in dog food. In the majority of these messages people cite various protein percentages. 40% in a kibble must surely be dangerously high for a pet who doesn’t work very hard, even a piece of fresh meat like for example a steak only has about 20% protein! But then there’s canned food, and if it only has 8% protein, it’s not going to give the dog enough to stay healthy!
Where to begin? First things first: stop comparing apples and oranges. You can’t fairly compare different types of foods that have entirely different moisture contents. Percentages are always relative, and the main factor interfering with correct comparison is the amount of moisture diluting the solid components (“dry matter”) of a food.
Dry kibble is highly processed and very concentrated, with a low moisture content of typically around 8-10% and a “solid” portion of 90-92%. In some ways this is an advantage, since because it’s so dry kibble has a long shelf life and you get a lot of product in a relatively small package. The disadvantage is that its unnaturally low moisture content requires that the dog compensates sufficiently by drinking extra water (and many don’t – but that’s material for another article), and the concentrated, nutrient dense product makes for disproportionately small feeding portions, often causing owners to overfeed.
On the flip side, less concentrated foods with a more natural moisture content of about 65-75% only contain a solid portion of 25-35%. The added moisture directly provides what the body needs to process food, without the dog having to compensate.
Let’s have a closer look at the nutritional composition:
I will use fictional products for this example, with a guaranteed analysis of 42% protein, 22% fat, and 10% moisture. It has an ash content of 12%, leaving us with a carb portion of 14% to make up 100%. It contains 4,000 kcal per kg (=1,818 kcal/pound), and one measuring cup holds 4.5 oz of it, delivering 512 kcal. Guaranteed analyses show minimum and maximum values, not averages, but for the sake of this example we will assume these values are the actual average content. In reality this is not the case and you would have to get this information from the manufacturer.
The majority of dog owners feed kibble as-is, dry right out of the bag. Let’s look at how food composition and percentages change if we add water directly to the kibble in the bowl. Keep in mind that water doesn’t add any calories, protein, fat, etc.
|Dry kibble only||Adding 1 cup of water||Adding 2 cups||Adding 3 cups|
|Dry food amount||4.5 oz||4.5 oz||4.5 oz||4.5 oz|
|Weight of added water||–||8.36 oz||16.72 oz||25.08 oz|
|Total serving weight||4.5 oz||12.86 oz||21.22 oz||29.58 oz|
|Total protein content||1.9 oz||1.9 oz||1.9 oz||1.9 oz|
|42.0 %||14.7 %||8.9 %||6.4 %|
|22.0 %||7.7 %||4.7 %||3.4 %|
|Overall Moisture %||10.0 %||68.4 %||80.8 %||86.2 %|
Now, let’s compare a number of different foods by “mathematically removing” all of their moisture, looking at the solid portion (dry matter) only, in the same serving size of 4.5 oz by weight:
|Dry kibble example
||Canned food example
||Raw sirloin steak *||Plain nonfat yogurt|
dry matter %
|As-is Protein weight||1.9 oz||0.4 oz||1.0 oz||0.26 oz|
|As-is Fat weight||0.99 oz||0.31 oz||0.2 oz||0.007 oz|
|As-is Moisture weight||0.45 oz||3.38 oz||3.26 oz||3.85 oz|
|Dry matter Protein %||46.67%||36.0%||79.64%||38.51%|
|Dry matter Fat %||24.44%||28.0%||16.73%||1.35%|
|Amount needed to supply 512 kcal||4.5 oz||12.73 oz||13.4 oz||32.0 oz|
|Contains oz of protein||1.9 oz||1.13 oz||2.98 oz||1.85 oz|
* USDA Choice Beef, top sirloin, separable lean only, trimmed to 1/8″ fat
All rights reserved. No part of this document may be used or reproduced in any manner without written permission, except in the case of brief quotations embodied in critical articles or reviews.