Kibble Math Part 1: Dry Matter Basis
When you read the ingredient panel on the back of a bag of dog food, it can only tell you so much. Ingredients are just one part of the puzzle… macronutrients (like protein, fat, and carbs) are important to consider too.
To be able to accurately compare foods, first we have to look at them on a “dry matter basis.” We do this because the moisture content of a food can distort the amount of protein, fat, and carbs in that food when they are listed in percentages. This can be especially distorted when comparing different types of food, like kibble vs canned vs raw, because the moisture content of each type of food is different.
Let’s look at an example. The following are guaranteed analyses from one canned food and one kibble food.
These two foods are both the same brand and same formula, but one is the canned version and one is the kibble. At first glance, these foods seem very different. The bottom one looks like it has much more protein and fat than the other.
But when we convert them to a dry matter basis, it gives us much more accurate information about the true macronutrient content of these foods.
To do that, first we figure out what percent of the food is dry matter by simply subtracting the % moisture from 100. For our first food, that would be 100-78= 22% dry matter. For our second food, that would be 100-12= 88% dry matter.
From there, we divide each macronutrient (such as protein and fat) by the % dry matter, then multiply that by 100. Let’s try the protein from both of our foods above. For our first food, we have 9% protein divided by 22% dry matter = 0.409. Multiplied by 100, we have 40.9% protein. That is a huge difference! For our second food, 26 divided by 88 times 100 = 29.5% protein. Look at that – it actually has LESS protein than the other food, even though you would think the opposite if you were just comparing the labels!